For years I've been experimenting with ways to let indie authors design better book covers without any design skills or expensive software. First I made over 150, so that authors could use a program they are already familiar with. It's easy to open the templates, switch the images and edit the text, and save the file as a ready-to-use cover. But I wasn't satisfied, so I built my own. You can use it on any computer connected to the internet, and it will always be totally free for everyone. These are design 'hacks' - and it's usually easier to just hire a designer to do it right. Sep 18, 2013 Free Kindle Book Covers: How to Make a Free Amazon eBook Cover using Cover Creator Self-Publishing. But if you're determined to DIY, I hope my templates and resources will help. Before you start designing, make sure you sign up and get my free training so you can avoid the embarrassing mistakes that all first-time authors make with their cover design. You can start with this video on cover design basics, but you'll get much more when you sign up. ![]() ![]()
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This is a Free EBook on Guitar. The aim of this book is to introduce beginners to the basic concepts of the guitar and to provide further stimulus for intermediate players. Important techniques are given their own sections with exercises and examples provided. It includes an extensive section on amplifiers and numerous tips and advice on all aspects of the guitar. Music theory concepts are clearly presented and explained. Topics covered: ➲ Open Chords ➲ Arpeggios and Sweep Picking ➲ Harmonics ➲ Lead Guitar and Rhythm Guitar ➲ Harmonica and Guitar Combo ➲ Alternate Tunings ➲ Hammer-ons, Pull-offs, and Trills ➲ Tapping ➲ Scale Theory ➲ Intervals and Power Chords ➲ Vibrato Bar Techniques ➲ Flamenco ➲ Bending and Vibrato ➲ Muting and Raking ➲ Movable Chords ➲ Tremolo Picking and much more. ![]() ![]() ![]() You need Alphonso EBook Viewer to view this EBook. You will be prompted to download it for FREE when you open EBook. 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Shop with confidence. ![]() Harry leaves the Dursley's house and is picked up by the Knight Bus, but only after an alarming sighting of a large, black dog. The Knight Bus drops Harry off at Diagon Alley, where he is greeted by Cornelius Fudge, the Minister of Magic. ![]() ![]() He rents a room and awaits the start of school. In Diagon Alley, Harry finishes his schoolwork, admires a Firebolt broomstick in the window of a shop, and after some time, finds his friends and. At a pet shop, Hermione buys a cat named Crookshanks, who chases Scabbers, Ron's aging pet rat. Ron is most displeased. The night before they all head off to Hogwarts, Harry overhears Ron's parents discussing the fact that Sirius Black is after Harry. The students board the Hogwarts Express train and are stopped once by an entity called a Dementor. Harry faints and is revived by Professor Lupin, the new defense against the dark arts teacher. Soon afterward, the students arrive at Hogwarts and classes begin. In divination class, Professor Trelawney foresees Harry's death by reading tealeaves and finding the representation of a Grim, a large black dog symbolizing death. In the care of magical creatures class, Hagrid introduces the students to Hippogriffs, large, deeply dignified crosses between horses and eagles. Malfoy insults one of these beasts, Buckbeak, and is attacked. Malfoy drags out the injury in an attempt to have Hagrid fired and Buckbeak put to sleep. In Defense Against the Dark Arts, Professor Lupin leads the class in a defeat of a Boggart, which changes shape to appear as the viewer's greatest fear. For Lupin, it turns into an orb, for Ron, a spider. Harry doesn't have a chance to fight it. During a Hogwarts visit to Hogsmeade, a wizard village which Harry is unable to visit because he has no permission slip, Harry has tea with Professor Lupin. Harry discovers that the reason he wasn't allowed to fight the Boggart was that Lupin had worried that it would take the shape of Voldemort. This concern catches Harry by surprise, because Harry had been thinking even more fearfully about the awful Dementors. Snape brings Lupin a steaming potion, which Lupin drinks, much to Harry's alarm. Later that night, Sirius Black breaks into Hogwarts and destroys the Fat Lady portrait that guards Gryffindor Tower. The students spend the night sleeping in the Great Hall while the teachers search the castle. Soon afterwards, Quidditch moves into full swing, and Gryffindor House plays against Hufflepuff. During the game, Harry spies the large black dog, and seconds later he sees a hoard of Dementors. He loses consciousness and falls off his broomstick. Harry wakes to find that his trusty broomstick had flown into the Whomping Willow and been smashed in his fall, and the game itself had lost. Later, Harry learns from Lupin that the Dementors affect Harry so much because Harry's past is so horrible. During the next Hogsmeade visit, from which Harry is forbidden, Fred and George Weasley give Harry the Marauder's map, written by the mysterious quartet of Moony, Prongs, Wormtail and Padfoot. This map leads him through a secret passageway into Hogsmeade, where he rejoins Ron and Hermione. Inside the Hogsmeade tavern, Harry overhears Cornelius Fudge discussing Sirius Black's responsibility for Harry's parents' deaths, as well as for the death of another Hogwarts student, Peter Pettigrew, who was blown to bits, leaving only a finger. Back at Hogwarts, Harry learns that Hagrid received a notice saying that Buckbeak, the hippogriff who attacked Malfoy, is going to be put on trial, and Hagrid is inconsolable. The winter holidays roll around. For Christmas, Harry receives a Firebolt, the most impressive racing broomstick in the world. Much to his and Ron's dismay, Hermione reports the broomstick to Professor McGonagall, who takes it away out of fear that it may have been sent (and cursed) by Sirius Black. After the holidays, Harry begins working with Professor Lupin to fight Dementors with the Patronus charm; he is moderately successful, but still not entirely confident in his ability to ward them off. Soon before the game against Ravenclaw, Harry's broomstick is returned to him, and as Ron takes it up to the dormitory, he discovers evidence that Scabbers has been eaten by Crookshanks. Ron is furious at Hermione. Soon afterwards, Gryffindor plays Ravenclaw in Quidditch. Harry, on his Firebolt, triumphs, winning the game. Once all the students have gone to bed, Sirius Black breaks into Harry's dormitory and slashes the curtain around Ron's bed. Several days later, Hagrid invites Harry and Ron over for tea and scolds them for shunning Hermione on account of Scabbers and the Firebolt. They feel slightly guilty, but not terrible. Soon Harry, under his invisibility cloak, meets Ron during a Hogsmeade trip; when he returns, Snape catches him and confiscates his Marauder's Map. Lupin saves Harry from Snape's rage, but afterwards he reprimands him severely for risking his safety for 'a bag of magic tricks.' As Harry leaves Lupin's office, he runs into Hermione, who informs him that Buckbeak's execution date has been set. Ron, Hermione, and Harry are reconciled in their efforts to help Hagrid. Around this time, Hermione is exceptionally stressed by all of her work, and in a day she slaps Malfoy for picking on Hagrid and she quits Divination, concluding that Professor Trelawney is a great fraud. Days later, Gryffindor beats Slytherin in a dirty game of Quidditch, winning the Cup. Exams roll around, and during Harry's pointless Divination exam, Professor Trelawney predicts the return of Voldemort's servant before midnight. Ron, Hermione, and Harry shield themselves in Harry's invisibility cloak and head off to comfort Hagrid before the execution. While at his cabin, Hermione discovers Scabbers in Hagrid's milk jug. They leave, and Buckbeak is executed. As Ron, Harry, Harry and Hermione are leaving Hagrid's house and reeling from the sound of the axe, the large black dog approaches them, pounces on Ron, and drags him under the Whomping Willow. Harry and Hermione and Crookshanks dash down after them; oddly, Crookshanks knows the secret knob to press to still the flailing tree. They move through an underground tunnel and arrive at the Shrieking Shack. They find that the black dog has turned into Sirius Black and is in a room with Ron. Harry, Ron, and Hermione manage to disarm Black, and before Harry can kill Black, avenging his parents' deaths, Professor Lupin enters the room and disarms him. Harry, Ron, and Hermione are aghast as Lupin and Black exchange a series of nods and embrace. Once the three students calm down enough to listen, Lupin and Black explain everything. Lupin is a werewolf who remains tame through a special steaming potion made for him by Snape. While Lupin was a student at Hogwarts, his best friends, James Potter, Sirius Black, and Peter Pettigrew, became animagi (humans able to take on animal forms) so that they could romp the grounds with Lupin at the full moon. They explain how Snape once followed Lupin toward his transformation site in a practical joke set up by Sirius, and was rescued narrowly by James Potter. At this moment, Snape reveals himself from underneath Harry's dropped invisibility cloak, but Harry, Ron, and Hermione disarm him, rendering him unconscious. Lupin and Black then explain that the real murderer of Harry's parents is not Black, but Peter Pettigrew, who has been presumed dead but really hidden all these years disguised as Scabbers. Lupin transforms Scabbers into Pettigrew, who squeals and hedges but ultimately confesses, revealing himself to be Voldemort's servant, and Black to be innocent. They all travel back to Hogwarts, but at the sight of the full moon, Lupin, who has forgotten to take his controlling tonic (the steaming liquid), turns into a werewolf. Sirius Black responds by turning into the large black dog in order to protect Harry, Ron, and Hermione from Lupin. As Black returns from driving the werewolf into the woods, a swarm of Dementors approaches, and Black is paralyzed with fear. One of the Dementors prepares to suck the soul out of Harry, whose patronus charm is simply not strong enough. Out of somewhere comes a patronus that drives the Dementors away. Harry faints. Harry awakens in the hospital wing to hear Snape and Cornelius Fudge discussing the fact that Sirius Black is about to be given the fatal Dementor's Kiss. Harry and Hermione protest, claiming Black's innocence, but to no avail; then Dumbledore enters the room, shoos out the others, and mysteriously suggests that Harry and Hermione travel back through Hermione's time-turning device, and save both Black and Buckbeak. Hermione turns her hour-glass necklace back three turns, and Harry and Hermione are thrust into the past, where they rescue Buckbeak shortly before his execution. From a hiding place in the forest, Harry watches the Dementor sequence and discovers that he had been the one who conjured the patronus, and he is touched and confused to note that his patronus had taken the shape of a stag that he recognizes instantly as Prongs, his father's animagi form. After saving his past self from the Dementors, Harry and Hermione fly to the tower where Black is imprisoned, and they rescue Black, sending him away to freedom on Buckbeak's back. The next day, Harry is saddened to learn that Professor Lupin is leaving Hogwarts because of the previous night's scare. Dumbledore meets with Harry and gives him wise fatherly advice on the events that have happened. On the train ride home, Harry receives an owl- post letter from Sirius that contains a Hogsmeade permission letter, words of confirmation that he is safe in hiding with Buckbeak and that he was, in fact, the sender of the Firebolt, and a small pet owl for Ron. Harry feels slightly uplifted as he returns to spend his summer with the Dursleys. By, March 22, 2015 There is two things I'd like to note. Let's take a look at Sirius and Peter, two of James Potter's good friends. Sirius Black stands for loyalty and Peter Pettigrew for betrayal. Now, Sirius even stated, that he'd rather die than betray his friends. Peter - in contrast - actually went to Voldemort and betrayed them. Anyway, someone who stayed 13 years in prison - even if he was innocent - deserves some respect. Now let's take a look at the argument between Ron and Hermione about Scabbers and Crooks. ![]() May 2008 was something of a milestone for me as far as the modification of cylinder heads for more performance was concerned. It was 50 years since I performed my first cylinder-head flow test. The technique I used was crude, to say the least, but it worked. Looking back on it many years later, I realized I should have continued flowing heads using this original method, instead of being swayed by convention. My original method employed the floating pressure-drop measuring method described in Chapter 2. This was not because I had, even at the tender age of 15, figured out that a floating pressure drop was better; it was because I had no idea how else to do the job. But as events unfolded, I flew into the face of convention for one of the first times as far as high-performance technology was concerned, but it was hardly the last! This Tech Tip is From the Full Book,. For a comprehensive guide on this entire subject you can visit this link: SHARE THIS ARTICLE: Please feel free to share this post on Facebook / Twitter / Google+ or any automotive Forums or blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: Here is how events unfolded. Read David Vizard's How to Port & Flow Test Cylinder Heads by David Vizard with Rakuten Kobo. Porting cylinder heads is an art and a science. It’s like sculpting a. Book, How To Port & Flow Test Cylinder Heads. Vizard shows how to optimize flow paths through the heads, past the valves, and into the combustion chamber. The first flow bench was, in fact, my mother’s vacuum cleaner. I mounted the head to be tested (an A-Series head as per the Austin/Morris Mini engine) on a bare A-Series block. ![]() The head was equipped with a way to precisely open the valves. Then, for the intake tests, the suction side of the vacuum cleaner was located in the bottom of the bore and sealed, so there were no leakages at this point. The type of flow bench illustrated here is the floating-pressure type. ![]() Round up the minimal parts required, and you can build one like this on a Saturday morning. If you already have a block and vacuum cleaner, the rest of what is needed can usually be sourced for less than $75. Next, a spark plug with the middle removed and a piece of 1/4-inchdiameter copper tube glued in was installed into the spark plug hole. It was connected to a manometer, made of clear plastic tubing stapled to a 2 x 4-inch board. This was marked out in inches from –48 inches at the bottom through zero to +48 inches at the top. The plastic tubing was looped, so that the bottom of the “U” was formed about a couple of feet or so below the bottom of the 8-foot-long 2 x 4. A section of the U-tube was filled with food-coloring-dyed water until it reached the zero mark. As you can see from Figure 3.2, there is not much to this bench. It can be constructed in a few hours for a minimal expenditure. If you already have a shop vac, the rest of it costs probably less than $75. Here is how it works. The more open the valve is, the lower the pressure drop is, as measured by the manometer. At low valve lift, say, 0.050, the manometer can read (depending on the vacuum cleaner’s capability and the valve’s ability to flow air) anywhere between 60 and about 100 inches H2O. If the flow at a given lift is improved, the manometer reading at that lift drops. Let’s say that the stock head at 0.050 valve lift produced a reading of 80 inches. We then do some seat blending on the valve and head casting, and on the next test the manometer reading is 70 inches. This means the flow has gone up, so the pressure drop pulled by the vacuum cleaner is lower. To a first approximation, the flow has increased by the square root of 80 divided by 70. ![]() That works out to 1.069, or a 6.9-percent improvement. You can see that this bench primarily tells us whether or not the port is flowing better or worse. Also we can see that it does not test the head at a standard pressure drop, as does almost every pro-built bench. This standard pressure drop, as previously stated, is considered conventional practice and allows a uniform method to be used for quoting the CFM of flow produced. At this point, you may be thinking that not having the ability to determine the CFM is a small price to be paid to establish positive or negative trends in a head’s airflow capability. After having built my bench, I spent a couple of years wondering how I could get real CFM numbers off it, so I could swap flow bench war stories with the guys at Weslake (the big name in airflow at the time) with-out revealing both my youth and then-amateur status. As far as CFM measurement was concerned, I saw the light some years later during a conversation with an engineer who was somewhat older and more experienced than I. During our conversation he used some key words: “standard pressure drop.” Well, there we go—I realized that I could adjust the test pressure/vacuum so that it was a constant; and then I could calculate the CFM. It was not quite as easy as typing the words but that, in essence, was it. Over the next few years, I built increasingly more sophisticated benches until finally, during the early 1970s, I built a bench that conformed to British Standards for precision gas flow measurement. It was a 15-foot-long monster. It worked just fine and cost a small fortune but the payoff was a lot of flow work that was done for those porters who didn’t have a bench. In the late 1970s to early 1980, I even did some work on it for the McLaren F1 guys. ![]() A Rethink on Matters By the time the mid 1980s came around, I began to have second thoughts about using a standard pressure drop to test heads. The issue here was: What sort of pressure differences do we see between the port and cylinder on a live-running race engine compared with what was typically being used on a flow bench? In Smokey Yunick’s Power Secrets, the author went to some length to make sure we understood that a seemingly magic 28-inch pressure differential should be used. That, as of 2012, is practically an industry standard. But as I have already pointed out, a race or even a high-performance street engine does not see a fixed standard pressure drop. Here, we need to deal with the reality. At cycle number-1, the exhaust generated vacuum starts the intake charge moving into the cylinder way before the piston even starts down the bore. As the crank rotates farther we get to cycle number-2. This is normally considered the charge inducing stroke. In an ideal situation, cycle number-1 has cleared the combustion chamber and put a considerable amount of kinetic energy into the incoming charge before the piston starts down the bore. The result is an engine that can achieve a volumetric efficiency well in excess of 100 percent. The bottom line is a good exhaust system that is worth a lot of extra torque, horsepower, and, best of all, extra mileage. But to make all this work as intended, the cam must generate the right events around TDC. The curve of interest here is the red one. This represents pressure seen in the cylinder. The valve lift starts at the 315-degree mark. With the valve just 0.050 inch off the seat, the suction caused by the exhaust is 100 inches H2O, and the velocity between the seat on the valve and the head is 200 ft/sec. The induction system on a true race engine is, for the most part, exhaust driven. That means the scavenging pulse from the tuned exhaust pulls a far bigger depression in the cylinder than the piston pulls going down the bore. On something like an engine from NASCAR’s Cup series, this can amount to 120 inches or more at TDC during the overlap period. The draw on the intake port at TDC can be such that, even though the piston is virtually parked, the intake charge in the port can be moving into the cylinder at as much as 90 mph! When the valve is near wide open and the piston is traveling at peak piston speed (this is between 72 to 74 degrees after TDC), the draw is somewhat less. How much less? For a typically high-flowing two-valve head feeding about 1.2 cfm per cubic inch to the cylinder, the pressure drop is about 15 to 20 inches H2O at peak power. The red curve in Figure 3.4 is a smoothed curve of the pressure difference between the cylinder and the intake port throughout an induction stroke. Although the curve can vary quite substantially from one similar engine to another (due to relatively small changes in lengths, diameters, and cam characteristics), this curve is representative of a 620-hp, single 4-barrel 355-ci motor.The first point of the graph is that the draw on the intake valve/port is greatest at low lift, in which the suction reaches 100 inches H2O while the valve is at just 0.050 lift. This means testing at 28 inches at this low valve lift is far from representative of the real world. Therefore, your floating pressure-drop tests should use a high-pressure differential at low lift and a lower one at high lift. Current Conclusions All the forgoing leads to one conclusion: To more nearly simulate what happens in a running engine, intake flow tests need to be done at a high pressure drop at low valve lift and a lower one at high lift. This is exactly the situation that happens with a flow-test rig (Figure 3.2). An uncontrolled vacuum source, such as a shop vac, pulls a large vacuum when the intake valve is closed and a progressively lesser vacuum as the intake is opened. So running a floating pressure drop, as we are doing here, is actually a more realistic simulation of what happens in real life. At this point we have, with a floating pressure-drop bench, a flow testing situation that more closely mimics the pressure differentials seen in the cylinder/intake port of a running engine. So what are the advantages? Let’s quickly go through them again to be clear on the justification for adopting this procedure over the more normal fixed pressuredrop method. If the pressure drop is too low, the flow pattern that develops in the port, especially in the more critical regions close to the valve seat, is not the same as at the higher pressure drop seen in a running engine. If we use a pressure drop that is too low, the flow attaches itself to the port wall on critical curves, such as the short-side turn, without any significant flow separation. When these conditions exist, air is fed to the part of the valve circumference that is situated adjacent to the short-side turn, so that the flow is better than it typically is at a higher pressure drop. When the pressure drop is increased to something more nearly representing that seen in a running engine, the port velocity increases to the point where the air simply skips off the short-side turn and tries to exit the valve on the long side. As a result, a considerable section of the intake valve’s circumference experiences very little flow. If we take a low standard pressure drop test of, say, 8 inches and correct it to 28, the resulting number comes out higher than if we had flow tested at 28 inches in the first place. In practice, if pressure drops significantly below 8 inches are used, the flow in the port slows enough to stay attached even around a relatively tight turn. Running the flow bench tests and conducting high-to-low floating pressure-drop tests creates the same pattern of flow-reducing portto-wall separations that occur during real-world running conditions. From this, it follows that the most effective port modifications are achieved by addressing real-world flow patterns and improving the port shape to improve such patterns. The bottom line is that our cheapo flow-test setup is actually a better tool for developing an intake port than a $10,000 commercial flow bench used in a conventional manner. At this point, the only down side is determining just how many CFM the head is flowing when each reading is corrected to the common 28-inch pressure drop. Without this number, you won’t be able to make a comparison with other flow test results or be able to compare your work to others. This can be fixed relatively easily, but for now let’s consider the exhaust. Flowing the Exhaust Without making some fancier test equipment, we are not going to be able to flow the exhaust at reallife test pressures. Typically, when an exhaust valve opens, the cylinder pressure is somewhere between 70 and 120 psi. If you are intent on having a pump that develops this kind of test pressure, even for just the low-lift tests, be aware that you need about a 200-hp motor to drive the pump. Very few flow bench setups are capable of this. Although unconfirmed, I have heard that Ford’s Detroit division has a flow bench that can approach real-world pressure drops, and that it costs a mere seven-figure number to build. For the most part, we flow the exhaust at 28 inches and live with the fact that it is not the best way to do things. However, our budget bench, with its uncontrolled floating pressure drop, actually does a better job than a commercial bench at a fixed pressure drop. I can say that there is little to prevent using a commercial fixed-pressure drop bench, such as the SuperFlow 600, in a floating pressure-drop mode, which I address in Chapter 3. Quantifying Results My friend Roger “Dr. Air” Helgesen built a bench that worked along the same lines as this in the early 1980s and still uses it today to flow heads and intake manifolds. As usual, Roger adopted a singularly simple way to convert the pressure drop seen on the manometer to CFM at 28 inches with nothing more than a sheet of graph paper and a few calibration orifices. Just how this is done is our next subject. Establishing the Numbers Okay, so you have built a budget flow bench. While this may allow you to establish whether a move has increased or decreased airflow, it does not, at this time, allow you to compare your efforts with the rest of the head porting community. Within reasonable limits, that problem can easily be taken care of. These holes need to be machined to a very smooth surface. Make tolerances as accurate as possible (+/0.001 is acceptable). The hole sizes and X-Y coordinates are: • Hole 5: 0.210 Dia. On 4.30/3.40 inches • Hole 10: 0.296 Dia. On 3.95/4.10 inches • Hole 20: 0.419 Dia. On 3.05/4.30 inches • Hole 40: 0.594 Dia. On 2.10/3.80 inches • Hole 80: 0.840 Dia. On 2.05/2.5 inches • Hole 160: 1.185 Dia. On 3.70/2.40 inches Radius entry for all holes is 0.25 inch. This is machined so that the edge of the radius goes out to 80 degrees, not the full 90. The back of the 5 and 10 size holes must be chamfered with a 90-degree cutter. The 5-hole chamfer should be 0.460-inch diameter and 0.546 for the 10 hole. When using my early flow bench, I never made the connection between using a floating pressure drop and actually calibrating the setup to give CFM. Instead, I invested a lot of hours building my monster British Standards bench with all the corrections then known to man. A venture like this is not the sort of job I recommend to other would-be porters/ cylinder-head development engineers. Your time is better spent on developing heads and selling what you are producing. Doing otherwise means investing what is potentially a huge amount of time, effort, and money in a bench that, at the end of the day, serves you less effectively than the super-cheap floating-pressure-drop one I advocate here. However, if you want a little more than just a vacuumcleaner-powered bench for a greater range of pressure drop, by all means build it with more powerful motors. But let’s get back to reading out our results in CFM. Here’s where the revelation came in. For many years, I knew Roger Helgesen had a flow bench but the deal was we always hung out at my place (maybe that’s because the Serdi seat and guide machine was there). But one day I was at his house, where he had his flow equipment, porting bench, and tools. What an eye opener that was. If ever there was a guy who could come up with ultra simple ways of doing ultracomplex jobs it was Roger (Another good friend of mine christened Roger “Dr. Air,” and I always thought that to be a very appropriate moniker). What really caught my attention was the calibration plate Roger had made and the graph he was using to simply read off the CFM at 28 inches of depression. The plate is shown in Figure 3.5, and the dimensions to produce it in Figure 3.6. It has holes sized to flow 5, 10, 20, 40, 80, and 160 cfm at 28 inches of depression across the plate. Not only can you use this plate to figure out how much flow is passing through a head on a floating depression bench, but you can also use it as a reference tool for a regular bench, such as a Superflow. A few words about producing or acquiring a Helgesen plate: With Roger’s kind permission I have reproduced the dimensions here, so you can make your own. I trust you to not go into production with these and sell them. It is Rogers’s idea and I ask you respect that. If you are not in the position to make one, you can check to see what the availability is through Dr J’s Porting Supply. Let us assume at this point you have a plate; how is it used to give CFM at 28 inches? Here is how that is done. Step 1: Make sure your bench is sealed so no leakage takes place, except through the test piece. Position the Helgesen plate on the bench with all holes plugged with clay (or any convenient plugs). Step 2: Start with a reading on the manometer, with the plate completely blocked off for a “zero flow” depression test, and note the pressure drop seen on the manometer. Note this stalled depression. (If you did not make your manometer tall enough, the vacuum cleaner has now drunk all the water from it!) Step 3: Open the 5-cfm orifice and note the depression (when I was talking about machining this plate they were referred to as holes—now that we are flowing through them they are orifices). Step 4: Plug the 5-cfm orifice and open the 10; flow test and note the depression. Step 5: Open the 5and 10-cfm orifices together and again note the depression. Continue in 5-cfm increments until all the orifices are open and you have recorded the depression at each 5-cfm increment. Step 6: Get a couple of large sheets of graph paper, the larger the better. I recommend something like 20 x 20 inches. Then for the intake, make a graph as shown in Figure 3.7. If you plot out your results, you should get a similar curve. Where it starts and finishes is totally dependent on the vacuum/pressure source you are using. Step 7: When you have a curve for the intake, repeat the test but use the blower side of the vacuum cleaner and reverse the plate. Step 8: Blow through all the holes in the same progression used for the intake and make a graph for the exhaust. You can now flow a head and get some respectably accurate flow figures for comparative purposes. Accuracy—How Good? Although what we have done here is very basic, it can produce results comparable to benches costing $10,000 or more and considered the industry’s standard. There are, however, many points at which errors can creep in and considerably reduce the accuracy of your results. Let’s start first with leakages. For the numbers to stand even a halfway decent chance of being accurate, the bench must not leak at any point. The voltage input to the motor influences the amount of suction a vacuum cleaner or any electric air mover can produce. You must monitor the voltage at the motor input and make sure you test at the same voltage each time. For the record, Dr. Air has a step-up transformer that increases the line voltage from whatever it may be (it varies between 110 and 115) to 130 volts, and then a rheostat device is used to adjust it to 115 volts. By plotting the individual orifices against the depression, you can develop a graph like this. You can then convert the subsequent pressure drop to CFM. The way the calibration plate is mounted on the flow bench also affects the readings. The ideal situation is to mount a box, which can be made of wood but must be airtight, about 9 inches down each side (9 x 9 x 9) with a 5-inch hole in the top, and whatever size hole mates up to the block or whatever you are using to simulate a block. Place the calibration plate directly over the 5-inch hole in the box and flow test it. If the plate is mounted on top of a bore even as large as 4 inches, there is a residual effect from the downstream velocity of the air and the plate flows about 2 to 3 percent higher than if flowed into an open box. Big changes in temperature and pressure also affect the reading, but this is only minor if the bench is in a constant indoor temperature. If there is any doubt about the figures, recheck the depression with the plate at, say, 160 cfm. Using this reading, correct the numbers up or down by whatever percentage of error is seen. Note: When the depression falls between 160 inches and 15, the highest degree of accuracy is achieved. If the depression drops much below about 6 inches at high valve lifts, you can figure that when corrected they could read a little higher than they should. Just how much is dependent on how severe any flow separation on the short-side turn is at the higher pressure-drop readings I am advising you to use. Summary If you have built a bench along the lines I’ve suggested, then at this point, you have a bench that was cheap to build and can deliver CFM numbers. The next step for an upgrade here is to write a spreadsheet program that does the number crunching for you. I have written a relatively simple Microsoft Excel program that allows me to input the depression numbers into my computer and subsequently prints a professional-looking set of graphs of the flow tests, complete with my business details along the top of the paper. Can a low-power shop vac be used as a pressure/vacuum source for a flow bench intended to flow typical small-block V-8 heads? You might guess this Sears 2½-hp, 6-gallon unit cleans but cannot flow a head; but with a floating pressure drop, this unit got the job done in spite of its marginal power. You may say that’s all well and good, but I am not into writing my own programs. That is not really a problem. But whether you can write programs or not, I have a simple question here: How would you like to upgrade what we have built so far with an electronics package? Such a package costs about $1,000. It allows your bench to read out in corrected CFM and directly integrate with your computer, so you can do fancy printouts. Well, in practice you have two companies that I know of that can be of great help with this, so that’s our next topic. Budget Computerization Okay, you have built the budget flow bench detailed so far. While this may allow you to see moves/ alterations that help or hinder and to determine CFM flow, it does not necessarily allow neatly printed comparisons of your efforts with the rest of the world. Nor, without considerable programming yourself, does it produce an analysis of what has been achieved such as flow efficiencies, port velocity, velocity gradients, and the like. Although there may be others, Audie Technology and Performance Trends are two companies I have dealt with that have very cost effective products that are professional quality but well within the reach of the home-based porter. Budget Bench Electronics Let’s look at how to take the floating depression bench just described, and substantially upgrade it to a professional-grade piece of test equipment. This includes an electronic readout in CFM, pre-corrected to the depression of your choice (probably 28 inches), and that alone might convince most of you wanting a more up-market bench to take the plunge. But that is far from all that is dealt with here. If you hook up your bench to a computer, you can record data with a push-to-read button that, while held down, averages the readings for as long as you do so. In addition, the system can also screen-display graphs of your porting efforts as well as print out professional-looking reports with your name on the top of the sheet (customers like this). Probably the best news is that you are only out of pocket by about $750 or so in 2012 dollars. If all this sounds appealing, let’s make a start on why and how to get from here to there. You don’t need to have moved that much up the ladder from novice to realize that maximizing power means maximizing cylinder head capability. Everything else in the loop is developed simply to make the most of the cylinder head’s capability. If we further analyze the performance equation, we find that at least 70 percent of a cylinder head’s performance capability is airflow related. The upgrades and accuracy tests, which I conducted with the aid of engine builder/tech writer Bob McDonald, brought our floating depression bench to full professional capability. This allowed it to meet the needs of those who port and prep high-dollar, four-valve heads for equally high-dollar clientele, as well as the more regular home-porter applications. But, in our case, meeting the needs of a high roller is maybe not quite as important as meeting the needs of the racer on a tight budget, and that probably includes most of us. Plenty of drag and circle-track race classes limit head castings to less-expensive, production-style items. This puts a greater emphasis on even small flow differences; and if you want to win, it’s important that whatever you have is better than whatever your competition has. Though it’s not the only category to do so, the IMCA racer in the United States falls squarely into this group. Since the engine can be claimed for a fixed fee, it’s good to get power without parting with a bunch of cash. If you are building an engine for this or a similar class of racing, you have to ask yourself: Just how much money can I afford to give away to be competitive? Like it or not, time and money are closely linked. We may resent giving away a pair of heads with an $800 porting investment, but not feel nearly as bad parting company with similar heads we have personally spent 10 to 15 hours porting. The bottom line is: Most racers have far more surplus expendable time than surplus expendable income! You don’t have to tour many head shops to realize the most popular bench used by pros is the SuperFlow 600—possibly with electronic support. You probably also understand the reason you don’t have one of these benches is because it can cost as much or more than the race car you are planning to build. So, for most racers and enthusiast engine builders, a $10,000 to $15,000 bench is simply out of the question. The electronic support system I am going to cover is not. Audie Technology Within pro engine/cylinder head circles, Audie Technology is well known. This company produces, among many other things, the Flow Pro data acquisition unit that is an add-on for non-computersupported benches such as the big SuperFlow units. It also produces the cost-conscious Flow Quik, which sells for about $750, and is not a flow bench in itself but more a means of measuring flow. By adding this unit to an existing flow bench, we can achieve as much as can be done with a commercial flow bench but at a fraction of the cost. Accuracy and the Budget Any piece of measuring equipment that comes in at less than 1/10 of the cost of its principal competition might rouse some concern about functionality and accuracy. Since the Flow Quik is a measuring instrument, tech writer/racer Bob McDonald and I decided to put it through its paces and pass on that info to possible end users. Our plan was to check ease of use, repeatability, and, most importantly, overall accuracy. To expedite matters, Audie Thomas of Audie Technology shipped us the Flow Quik unit the company exhibits at the Performance Racing Industry show. Bob and I extensively tested it for a full week and what follows are the results. Introducing the Flow Quik Audie’s show unit has a dummy cylinder mounted on a flow box. This is connected via a 2-inch-insidediameter (I.D.) hose to the tube containing the measuring device. Upstream and downstream of this orifice is a pressure tap, which is connected to a box of electronics. The pressure transducers in this box convert air-pressure signals to electronic signals. These signals are transmitted to a microprocessor and the data is displayed as CFM on an LED readout. For the tests done here, a Helgesen plate (left) was used as a reference to test the Flow Quik’s overall accuracy. On the right is the flow measuring device housed in the Flow Quik’s measuring tube. The first tests we ran were to compare the end results of a run at 28-inch fixed-pressure drop and another run with a floating pressure drop. To do this, we ran the bench both ways and used our Helgesen calibration plate as the test piece. In the floating mode, the test pressures seen on the bench by the Flow Quik ranged from about 72 inches to less than 10. The resultant corrected numbers and the accuracy produced (compared to corrected 28-inch numbers) are shown in Figure 3.15. A calibration tube, which is installed in the system, is supplied with the Flow Quik. The readout is adjusted to 80.9 cfm on the 28-inch scale. In this instance, the unit was calibrated with the 80-cfm orifice in our Helgesen calibration plate, hence the zero error at that point. As far as overall accuracy, it is far better than the majority of benches in the performance world. Compared with a typical commercial bench, the Flow Quik, from 40 cfm up, averages about the same error; i.e., about 2 percent. Although overall accuracy is important for us to make comparisons from different benches, the number-one requirement for a head porter is consistency from one month to another. We were able to make a relatively good check of that because of a dramatic weather change during our testing period. Readings taken seven days apart showed the Flow Quik’s repeatability to be about 1 percent. At the end of the day, we can say that the Flow Quik’s accuracy against a calibration plate was as good as a bench costing ten times as much. Computer Program At this point our tests turned to determining just how well, given the floating pressure drop, the Flow Quik’s performance translated into accurate and repeatable results on a real head. The LED readout on the Flow Quik box is only one function of it. This box has connections to allow the output from the microprocessor to be input into a computer. Also a push-to-read or take-reading button can be used to transfer the measured CFM to a Flow Quik program. The Flow Quik program allows the user to type in info relative to the head being tested. This head-spec info is then used to calculate many factors important to the serious head porter. Such things as valve discharge coefficient and port velocities at various pre-determined points are calculated and displayed. The take-reading button also greatly improves accuracy and repeatability by virtue of its averaging capability. For our tests, a 5-second interval was used as the averaging period. The “take-reading” button (left) averages the readings for as long as the button is held down. A 5-second “hold down” interval produced repeatable results. The graph (right) is what comes up on the computer screen. To put the Flow Quik through its paces, we used a Holley 23-degree, high-performance street small-block Chevy head. This pushed the Flow Quik to what we perceived to be about 80 percent of its limit with a dual motor-vacuum source. Head Setup Although installing the test head on this bench was the same as with any other bench, there was a difference from, say, a SuperFlow bench: The Flow Quik does not directly sense and compensate for any extraneous leakage. Although leakage at any point other than the intake valve can be deducted from manual readings, the same cannot be done in the computer-supported mode if accurate number crunching is expected. This means making sure there are no leaks in the equipment itself. And because the test depression goes so much higher than on a regular bench, the springs holding the valves closed must be at least twice the stiffness. Test Pressure Comparisons Our first tests with the Holley head were made in floating pressure drop mode. This allowed the Ametek motors to pull whatever maximum test-pressure differential they were capable of. At 0.050 inch lift, 62 inches of vacuum was seen across the intake valve of the test head. As the lift increased the pressure dropped; so at 0.700, it was down to just more than 12 inches. Several tests run under identical conditions showed readings spanning less than 1 percent. Our next test was designed to simulate a lesser pressure/vacuum source. To do this, we introduced a fixed leak prior to the measuring point, to bleed off some vacuum. The curves starting high on the left and dropping toward the right show the test depression used for each of the two flow tests. Regardless of the big difference between the red and green test depression curves, the Flow Quik still corrected the flow numbers to generate the nearly identical red and green flow curves seen here. Executing the same test but with about half the vacuum, and comparing the readings with the fullvacuum source, produced the results shown in Figure 3.15. You can see the microprocessor computations compensated and corrected, to within a close margin, for the difference between the floating test pressure and the 28-inch fixed test pressure. Comparing these numbers with those achieved from a freshly calibrated SuperFlow 600 (using a fixed 28 inches) we saw a maximum difference of 2.8 percent below 0.200 lift and 2.2 percent above. The average difference from 0.050 to 0.700 was only 0.9 percent, with the Flow Quik showing slightly more flow than the SF 600. The bottom line: Our test Flow Quik unit produced figures (which could be expected to vary a little from unit to unit) that are closer than typically measured between two conventional and supposedly identical fixed-depression benches. The Shop-Vac Test The last and, from our point of view, the most important test was to run the Flow Quik with a regular shop vac. Since the point was to see if a typical vacuum cleaner could be used, it was not part of the plan to get the biggest one we could find. The goal was to see if we could get respectable CFM readings with an average shop vac. Figure 3.16 shows that this is possible. Although about at the limit, a 2½-hp Sears shop vac is capable of sufficient pressure/vacuum to deliver the results shown by the yellow curves in this graph. Until the 220-cfm mark, the correlation between results produced by two powerful Ametek vacuum motors and the shop vac was extremely good. Above that, only a modest error of up to 1.5 percent was shown. Conclusions Our first thoughts on the performance of the Audie Technology Flow Quik were that it far surpassed expectations. Ease of use, speed, and accuracy were far beyond what you normally expect of such a cost-conscious unit. In its least expensive form, the unit from Audie sets you back about $650. Add to this the cost of building the bench as detailed earlier, a dial gauge, and a means of opening valves, and you are in business. If the shop-vac selected is about 6 hp, like a big Sears unit, I estimate a realistically accurate range of flow capability of about 330 cfm. Think about this: You can have a professional-capability floatingdepression bench for under $750. Port two sets of heads, and you have more than recovered your investment! Performance Trends Another recognized name for flow bench testing is Performance Trends. In fact, SuperFlow resells Port Flow Analyzer software, Pitot tubes, swirl meter, and other accessories with its flow benches. A swirl meter can make important contributions toward developing heads that produce wide power curves. I have used three different types over the years, including a paddle-wheel type (from Performance Trends), a Torsional torque one (no longer available), and a honeycomb one (as seen here from Audie Technology). Performance Trends offers a couple of options for the DIY flow-bench builder: Port Flow Analyzer software and Black Box II electronics. These can be fitted to almost any type of DIY bench, even older SuperFlow, JKM, and FlowData benches. Their sales and tech staff ensure that you get the correct system for your DIY bench. Performance Trends also offers calibration services for a small charge; you simply provide them flow readings from your bench with orifice plates of various sizes. Using this data, they tell you the full-scale CFM readings for your particular bench; so your bench, with their software, now matches the rest of the industry. For those who want to start building a bench from scratch, Performance Trends offers a system called EZ Flow for about $999. This kit includes software and electronics, and plans for building a bench from PVC tubing. PVC tubing and fittings are especially suitable because they are inexpensive, easy to work with, and they do not leak. That is a good point because the major drawback of a DIY bench is air leakage. Unless multiple layers of paint are applied, significant amounts of air can leak right through plywood if enough care is not taken during prep and assembly. EZ Flow kits come in two sizes, for either 4or 6-inch PVC. For flows up to about 150 cfm, the 4-inch system works fine. For anything greater, up to around 500 cfm, you need to build it out of 6-inch PVC. The EZ Flow system also includes critical machined components, the flow orifice, and the head adapter. If you don’t have a machine shop, or want to get running right away, this is a huge time and cost saver. The head adapter for the 6-inch EZ Flow allows for easy replacement of the head-bolt adapter plate and bore sleeve. This means you can quickly change your bench to flow different-style heads and engine bores in minutes. The standard 4and 6-inch systems come with a head adapter and components to accommodate a small-block Chevy and small-block Ford bolt pattern with a 4.030-inch bore. Other Bench Sources After building my British Standards compliant monster bench and using it for several years, I moved from the UK to Tucson, Arizona. This was my second introduction to SuperFlow airflow benches. I had used a small 110 for accuracy comparison to my home-built bench while still living in the UK. But that was only a few hours of experience. The Saenz J-600 bench I currently use. It comes fully instrumented with the Audie Technology electronics and computer software. Also available is the automatic valve opener seen here, which speeds up testing significantly. In 1976, the publisher I was writing for acquired an SF 300, which is the big bench that evolved into the SF 600. I have put literally thousands of hours on such a bench. I still, as of 2012, regularly use an SF 600 bench with all the Audie Technology addons. The only difference between what I do on this bench and what most others do is that I use a sliding scale of pressure drop, the same floating pressure drop I described earlier in this chapter. Another bench I am cur-rently testing on is the Saenz J-600 bench, built in Brazil. What I can say is that this Saenz unit lends itself well to the floatingpressure-drop measurement technique because it pulls a lot of vacuum. Combine this with the fact it comes equipped with the Audie Technology flow measuring gear and software, and you get a bench that delivers results in a standard form while measuring with a sliding scale (floating) pressure drop—all good for doing the job right. Written by David Vizard and Posted with Permission of CarTechBooks GET A DEAL ON THIS BOOK! If you liked this article you will LOVE the full book. Click the button below and we will send you an exclusive deal on this book. Filed Under:. Before getting into the subject of physically modifying cylinder heads, let’s look at the history and basic logic and techniques involved with establishing a cylinder head’s number-one criteria: airflow. A working knowledge here allows a better understanding of all the head characteristics we are attempting to improve and how they may each affect the others involved. Make no mistake; in the quest for optimal head configurations, you need to make many compromises. This Tech Tip is From the Full Book,. For a comprehensive guide on this entire subject you can visit this link: SHARE THIS ARTICLE: Please feel free to share this post on Facebook / Twitter / Google+ or any automotive Forums or blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: The information covered in this chapter will help you make many better decisions down the road. As you have probably guessed already, measuring cylinder heads’ capacity to flow air is our number-one priority. After that, there are a number of secondary but none-the-less vitally important factors we need to measure and manipulate in the manner most beneficial to us. Such factors include port velocity, velocity distribution, wet-flow characteristics, swirl, and the like. All of these factors tend to start at one focal point: the standard pressure drop. Why the crosshairs? Getting it right means making it happen here, and by “happen” I mean cylinder pressure. To produce the highest cylinder pressure means feeding the cylinder with as much air as possible. Next, the charge has to be effectively burned and then dispelled through the exhaust port as efficiently as possible. The red dot represents a prime position for the spark plug tip; the green one is poorly positioned for a high-compression engine. The Standard Pressure Drop Air is an elastic medium and, as such, its rate of flow has to be measured under specific conditions. An analogy of where I am going here is to imagine you have to measure the length of several different elastic bands for comparison. Just how long these elastic bands are depends on how much tension they are experiencing. To make an across-the-board comparison, we need to have a fixed amount of tension. In this case, we need to know how long these bands are when stretched by a tensile load of 2 pounds. In this instance, we call that our standard load. By adopting a standard load we are eliminating the principal variable that changes its length, without actually involving any properties the band may have in the first place. Much the same situation applies when it comes to the measurement of airflow. The greater the suction on a given orifice, the greater the volume of airflow through that orifice. To make a comparison across the board for a number of different orifices, we have to fix the amount of suction, so that it is the same for each orifice tested. Figure 2.2 shows why we must, for comparative reasons, have a standard pressure drop or, at the very minimum, quote it on our test results. As of 2012, common practice when testing cylinder heads is to use a fixed “standard pressure drop” throughout the valve opening range tested. Although going this route may make the comparison of results fast and convenient, it can also, as we shall see, compromise port development. Until the 1990s, when the International Automobile Federation (FIA) let the reigns go on naturally aspirated F1 engine development, it seemed the heyday of rapid piston engine development was during World War II. Back then, each engine manufacturer used a test pressure drop of its own choosing, so there really was no universally accepted pressure drop. As postwar civilian companies, such as We slake in England, got into flow testing for engine development, nothing much changed. When it came to test pressures/vacuums, it was each to its own. But then along came the ever-innovative hot rodder Henry “Smokey” Yunick. Smokey was not only something of a rascal (and, in performance-automotive circles, a famed one at that), but a rascal who was always pushing boundaries when it came to making power from piston engines. I knew Smokey personally, but since his passing in 2001, I wish I had taken advantage of numerous opportunities to spend more time with him. Smokey was one of the great performance-engine innovators of the later part of the twentieth century. He was also very vocal about his theories and findings and any other of his opinions he thought you should know about. An AFR small-block Chevy combustion chamber. This shape is the result of flow testing and then qualifying it on the dyno. He was the kind of a guy who devised equipment to test theories almost at the drop of a hat, if it looked like it might bring about any kind of progress. After utilizing any possible advantages, he was ready to share what he found with the rest of the performance community. It’s worth mentioning that, apart from having a must-read autobiography, Smokey did a book for Car Tech. Here, I can say with all certainty that you may want it in your auto-tech library. Anyway, returning to the subject of the standard pressure drop, Smokey built a number of flow benches and his final one was a monster that did a whole lot more than just deliver CFM numbers. Early on, Smokey made it one of his missions to find out which standard pressure drop value, in a meaningful manner, translated observed flow improvements to possible power improvements on the dyno. Starting at a relatively low test pressure, he ran the gamut on this and declared that tests had to be done at a minimum of 28 inches of water (H2O) depression for a flow bench improvement to consistently show up as a power improvement on the dyno. The majority of engine builders in the United States held Smokey in high regard, and he was also widely read, so this 28-inch measurement became an accepted standard for the performance-engine building community. So when you see airflow test results in various publications, and in my books, you find that the test pressure at which the flow is quoted (as opposed to actually being measured at) in the charts and graphs is with 28 inches H2O pressure drop. So was Smokey right in claiming that at least 28 inches was needed for that meaningful translation of results from the bench to the dyno? Well, although test results can be converted from one test pressure to another, the results, when corrected from a lower to a higher test pressure, don’t quite tally (for reasons I address shortly). Certainly, there was more than enough justification for Smokey’s claims here, but it is still a few steps short of what we may do for optimal port development. What I want to do here is to address how relevant a steady-state flow test is as far as correlating it to the pulsing flow seen in a running engine. Let’s go back to when the other guys kept telling me a flow bench was not even worth its weight in paper because of the difference between steady and pulsing flows. The difference in flow seen on a bench versus that within a running engine is dramatic. At first sight, this makes the other guys’ argument appear very valid, but the following was my counter argument on this subject: “If we open a valve and test the flow at whatever pressure drop is chosen, we can say that in a running engine the flow will, for all practical purposes, be steady if it is considered over a short enough period of time. In other words, if we looked at the flow past the intake valve for a period of, say, one millionth of a second, the flow at the beginning of that period essentially is the same as the flow at the end of that millionth of a second. So we can say, within close limits, the flow in a running engine, when taken over a small enough time increment, is virtually steady. The implication here then is that our flow bench, on this score, does reasonably simulate what goes on in a running engine.” In the 1980s or so, a top Japanese engineer, apparently with a large amount of funding, researched this subject right down to the bare bones. At the end of the program he proclaimed that, for all practical purposes, a steady-state flow test was a meaningful test because it substantially related to the pulsing flow seen in an engine and the dyno results produced. So, now we have an accepted standard pressure drop from which to get fully serviceable flow figures and strong evidence that the steady flow seen with the bench still correlates well with the pulsing flow seen in a running engine. Although we have now arrived at what are now widely accepted practices, I am far from finished on the subject. I am not finished because 28 inches can present its own set of test problems. Real-World Test Pressures So why can 28 inches of test pressure drop be a problem? The short answer is that it is a compromise. A higher test pressure allows the development of better ports, especially the intake, but stepping it up can present real bench-motor power problems. In an effort to overcome this, I have seen flow benches that required two 50-hp electric motors to run. The space, time, money, and effort required to build a bench like this is nearly prohibitive and, as we shall see, unnecessary. The problem is: If you want to test a typical big-block Chevy head or even a really good small-block head, you need a lot of amps for the inevitably large electric motors needed to produce the required vacuums/pressures. This means buying a pretty stout commercial flow bench at something between $6,000 and $18,000, or building your own bench with as many as six high-powered vacuum motors. On top of that, you may have to have your shop or household electricity supply up-graded to deal with the amperage involved. Here is what happens as the test pressure and, consequently, the port velocity goes up. At low test pressures (left) the air has a better chance of staying attached to the port floor, and as a result the entire circumference of the valve is used to good effect. When the test pressure is increased to that more commonly seen in a running engine, the flow detaches from the short-side turn, and the higher-velocity air attempts to exit the long side, which is already busy passing air from the long side. A drop in efficiency, which is otherwise unaccounted for during normal pressure-drop corrections. Corrections In the early 1970s, Neil Williams, the founder and driving force behind Super Flow, introduced the compact Super Flow 110 flow bench. I believe this was the first commercially available flow bench and it tested heads using a 10-inch pressure drop. I had the opportunity to do a comparative check on one of these benches in late 1973 at Piper Cams in England. For all its simplicity, it did produce results that compared well with the ones I saw on my monster BSI flow bench, which tested at 20 inches for small heads and 15 or so for larger heads (such as Chevy big-blocks). The pressure differences on a bored and stroked small-block Chevy (final displacement: 441 ci). This was a little large for the heads involved, but the trends we need to appreciate can be seen here. When the intake valve was 0.070 off the seat, the suction from the exhaust as measured in the combustion chamber (red curve) was 100 inches H2O while the suction caused by the piston never exceeded 50 inches H2O. This graph also shows that the intake port velocity (blue curve), while the piston is parked at TDC, is no less than 120 ft/sec. As mentioned earlier, you do have an option here to correct a, say, 10-inch pressure drop to 28 inches with a mathematical correction. The problem is that this type of correction is only satisfactorily valid when corrections are small, and you are testing a simple orifice or a straight port with absolutely no bends in it. Any time a seat and valve enters the equation, errors made in corrections from a low to a high test pressure have a greater impact on flow. Equally as bad is the fact that the corrections almost always produce artificially higher flow numbers. But there is a fix for this problem, and it’s one that has absolutely no downsides. The fix makes testing more meaningful, reduces the cost of a bench, and you are able to do it all without having to invest in any workshop electrical upgrades. To see how all this works, let’s get back to test pressures. Floating Pressure-Drop Testing As I just mentioned, the Super Flow 110 bench tested at 10 inches of pressure drop. When doing so, the port velocity is substantially lower than when that same port is tested at 28 inches. At 10 inches, the air could be traveling at a speed just marginally less than that needed to produce flow separation around the short side turn (Figure 2.7). When the flow stays attached, the air makes better use of the entire valve circumference. Under these conditions, the valve is more efficient. When that same situation is tested at 28 inches, the air in the port may not make it around the short-side turn in anything like the same way and the flow past the valve adjacent to the short-side turn is consequently disrupted to a far greater extent, thus cutting the overall flow. However, the typical mathematical adjustments applied to correct a 10-inch measurement to a 28-inch result do not work well for this. Also it is a problem that it results in a port that may work at 10 inches but be far less effective at 28. At 28 inches, the flow separation influences the development of the final seat and port used. In other words, that higher test pressure goes toward solving a problem that did not even show up at a 10-inch test pressure. Taking stock of the situation so far, we can say that we need higher test pressures, but the downside is the requirement for increasingly larger pump motors. The situation looks bleak until we stop to look at the cyclic pressures that exist in the intake port of a high performance engine. In Figure 2.8 we see the pressures that occur within an intake port of a street/strip 441ci (7.23-liter) small-block Chevy during the induction phase are far from being a steady 28 inches. During the overlap period, where valve lift is relatively low, we can see a depression across the intake valve as high as 100 inches, and it can be much higher in an all-out-race, two-valve engine. This low pressure is brought about by the negative pressure wave arriving at the exhaust valve and it functions as a means of extracting the combustion residuals. It does so with sufficient amplitude to pass through the chamber and act on the intake port. This high-exhaust-generated vacuum starts the intake flow into the cylinder well before the piston even starts down the bore. Do not underestimate the value of this effect. In practice, it can make or break the degree of success seen on the development of a high performance engine. Although at high valve lift, the pressure drop across the intake valve for our example is some 50 inches we find that for a highly developed engine with decent seat and port design, depression is more in the 15to 20-inch range. If in-cylinder pressure measurements show anything much more than that, it’s a sign of inadequate heads for the displacement/RPM involved. Now here is where we get a break. If we hook up a typical vacuum cleaner to a cylinder head and progressively open the intake valve, we find the pressure drop at low lift is high and at high lift is low. That is exactly what we are looking for. Accepting a floating pressure drop is the key that immediately unlocks the door leading to the building of a very simple yet extremely effective flow bench. The construction of such a bench is explained in Chapter 3, but I first want to address the relative importance of the intake versus the exhaust. Intake Fixation? It is patently obvious that any cylinder head has two distinctly different ports that need to be developed to produce high-flow efficiencies for maximum power: intake and exhaust. The question being posed here is: Which of these two is the most influential toward the production of power? At first sight, it may seem to be the exhaust because, after the charge has been burned, the volume is so much greater. Let’s assume for the moment we are dealing with a naturally aspirated (non-supercharged) engine. At the point of exhaust valve opening, there is between 70 and 120 psi waiting to escape from the cylinder. When the exhaust valve opens, the flow velocity between the seats in the head and those on the valve momentarily exceeds the speed of sound. The green curve is the intake flow of a big-block Chevy 049 casting in stock form but with a 2.250 valve. The blue curve is for the same head ported. The solid red curve is for a head having a flow efficiency of 100 percent based on the valve O.D. In practice, it is helpful to look at the flow efficiency based on the throat diameter of the port (red dotted curve). In either case, the flow efficiency of most heads is a long way from the best that can theoretically be obtained. For the intake valve, the situation is far different. The greatest pressure available to drive the charge into the cylinder is that of atmospheric pressure (i.e., 14.7 psi). Worse yet, of that 14.7 psi, we can’t really use more than 1 or 2 psi at most. Therefore, we need to see the minimum drop across the intake valve for best breathing. From this, we can see it is going to be a lot harder to fill the cylinders than it is to empty them. In addition, if the cylinder fails to adequately fill due to poor induction efficiency, the engine’s power potential is reduced no matter how good the exhaust may be. So, initially at least, we need to focus on finding intake flow from a performance cylinder head. It is not until average flow efficiencies of the intake throughout the intended valve-lift envelope have exceeded about 60 percent that we need to start considering intake-to-exhaust flow ratios and the valve sizes involved. Flow Efficiency For a given pressure drop, there is a relatively well-defined limit for how much air can pass through a given area available for that flow. At 28 inches pressure drop, an opening like the size of the one created between a valve and the seat in the head flows 146 cfm for every square inch of available opening area. At this level, the aperture created is 100-percent efficient. Of course, the area available to flow in or out of the cylinder varies with lift. As the aperture geometry varies, so does the flow efficiency. At very low lift (0.0 to 0.050 inch), the gap at the valve seat resembles a venturi. At this size of gap, there can be some pressure recovery, so at these low lifts the valve seat configuration acts as a nozzle. Then the flow efficiencies appear very high and can often exceed 100 percent. However, that is more a function of how we determine what the 100-percentile figure is. In practice, a nozzle requires a different equation to compute its flow, hence the apparent anomaly here. Figure 2.9 shows the difference between a stock big-block Chevy head, a ported one, and the 100-percent mark that we should strive for. A similar high-efficiency situation at low intake lift can exist for a well designed exhaust port. Not only can very high efficiencies be realized at low lift, but also at lift values exceeding about 0.28 inch of the valve diameter. At these lift values, a steeply up-drafted port can start to take on the properties of a nozzle. As a result, the flow figures can appear extremely high and in certain instances exceed the 100-percent mark. I address flow efficiency more in Chapter 10. But it may help here to show some typical efficiency figures versus the figures seen if the valve and port were 100-percent efficient. Figure 2.9 shows this. Note how a typical stock port is usually barely more than about 50-percent efficient. If porting time is put into production two-valve heads, efficiency can be raised to 65 percent or more, depending on the casting involved. That, without resorting to bigger valves, is a 30-percent increase in airflow. What that can do for power output, especially if it is combined with a compression ratio (CR) increase, is very gratifying. Written by David Vizard and Posted with Permission of CarTechBooks GET A DEAL ON THIS BOOK! If you liked this article you will LOVE the full book. Click the button below and we will send you an exclusive deal on this book. Filed Under:. ![]() FROM THE AUTHOR OF THE BESTSELLING BIOGRAPHIES OF BENJAMIN FRANKLIN AND ALBERT EINSTEIN, THIS IS THE EXCLUSIVE BIOGRAPHY OF STEVE JOBS. Based on more than forty interviews with Jobs conducted over two years-as well as interviews with more than a hundred family members, friends, adversaries, competitors, and colleagues—Walter Isaacson has written a riveting story of the roller-coaster life and searingly intense personality of a creative entrepreneur whose passion for perfection and ferocious drive revolutionized six industries: personal computers, animated movies, music, phones, tablet computing, and digital publishing. At a time when America is seeking ways to sustain its innovative edge, and when societies around the world are trying to build digital-age economies, Jobs stands as the ultimate icon of inventiveness and applied imagination. He knew that the best way to create value in the twenty-first century was to connect creativity with technology. He built a company where leaps of the imagination were combined with remarkable feats of engineering. 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The author was transformed from a boring accountant-controller working 12 hours a day to an individual who found his passion and is now able to manage his and others' priorities by implementing the 4 Steps described in this material. Reading in and of itself has plenty of benefits for our minds: have shown that reading over the course of a lifetime (or even starting to read consistently when you’re well into your 60s and 70s) can prevent mental decline. Along with keeping your mind sharp and enlarging your knowledge base, reading can expand your sense of empathy, too. A 2013 found that when people were transported into the emotional travails of books' characters, they grew to become more empathetic in real life. So the act of reading is great, of course. But the way you’re reading also has an impact on your physical and mental health. In our technology-driven world, the paper book has been replaced by electronic devices — Kindles and Nooks, and even reading on your laptop or smartphone. Good old-fashioned books are no longer seen as practical. There’s something simple and special, however, about reading a classic paper book that e-books seem to lack. Recently, I was reading before bed while I drank a cup of chamomile tea, and I found that it not only relaxed me, but I fell asleep almost immediately, I slept soundly through the entire night, and I woke up feeling refreshed. I found myself pondering events and scenes in the book, the imagery glowing in my mind in place of my typically exhausting anxieties. I’m going to believe it wasn’t a coincidence: Putting aside my phone — which, in addition to texting, has access to the cyclical, distracting spirals of Facebook, Instagram, and Snapchat — and focusing on a tale that took me outside of myself, somehow, inexplicably, helped me feel better on many levels. Reading sharpens the mind and helps fight off dementias. Photo courtesy of Researchers have been examining the differences between reading regular books and e-books for years. Many of the studies have shown that reading old-fashioned books has plenty of advantages over e-books, which can be gateways to other electronic distractions, all of which screw with your sleep. This is why you should ditch the screen for printed pages. You're Missing Out On Important Information A 2014 study found that readers who used Kindles were less competent in recalling the plot and events in the book than those who used paperbacks. Researchers still aren’t quite sure why this occurs, but it might have something to do with being able to physically and visually track your progress in a real book. For thousands of qualifying books, your past or present print-edition purchase will soon allow you to buy the Kindle edition for $2.99, $1.99, $0.99, or free. ![]() “In this study, we found that paper readers did report higher on measures having to do with empathy and transportation and immersion, and narrative coherence, than iPad readers,” said Anne Mangen of Stavanger University in Norway, an author of the study, according to. “When you read on paper you can sense with your fingers a pile of pages on the left growing, and shrinking on the right. You have the tactile sense of progress, in addition to the visual. Perhaps this somehow aids the reader, providing more fixity and solidity to the reader’s sense of unfolding and progress of the text, and hence the story.” Digitization of text also means it’s likely to be more fragmented, full of disturbances and links that can lead you to anywhere on the Internet. Reading on an iPad with the ability to check Facebook provides an avenue to take “breaks” way too often. And in order to retain information, you need to read in long, undisturbed chunks of time. Using laptops or phones late at night to read doesn't make way for restful sleep, according to studies. Photo courtesy of E-Books Get In The Way Of Sleepytime A out of Harvard University found that reading an e-book before bed lessened the production of an important sleep hormone known as melatonin. ![]() As a result, people took much longer to fall asleep, experienced less deep sleep, and were more fatigued in the morning. “The light emitted by most e-readers is shining directly into the eyes of the reader, whereas from a printed book or the original Kindle, the reader is only exposed to reflected light from the pages of the book,” Charles Czeisler, lead author of the study, told the. “Sleep deficiency has been shown to increase the risk of cardiovascular disease, metabolic diseases like obesity and diabetes, and cancer. Thus, the melatonin suppression that we saw in this study among participants when they were reading from the light-emitting e-reader concerns us.” In contrast, reading an old-fashioned book can actually help you sleep better. By taking your mind off the things that you may normally stress about before falling asleep, a book can clear your mind and also make you sleepy, easing you into a full night’s rest. In addition, soft light being reflected off the pages of a book doesn’t signal to your brain that it’s time to wake up like the glaring screen of an e-book or phone. Putting away your electronic devices and focusing on a paper book creates singularity in focus. Photo courtesy of Screens = Stress Reading helps you de-stress faster or just as fast as listening to music, taking a walk, or having a cup of tea or coffee, according to a 2009. When researchers measured heart rate and muscle tension, they found that people relaxed just six minutes into reading. But reading on a device might cancel out this effect, and may even impact your stress levels negatively. Repeated use of mobile phones or laptops late at night has been to depression, higher levels of stress, and fatigue among young adults. Constant use of technology not only disrupts our sleeping patterns and throws off our circadian rhythms, but it fosters a shorter attention span and fractured focus — online, we jump from meme to meme and link to link, checking Facebook intermittently. Social media and technological distractions also always seem to foster guilt and regret, and before we know it, three hours have passed and our brains feel like mush. It's hard to put my finger on what exactly draws me to paper books, and makes me avoid electronic ones. Perhaps it's the tangible qualites: Turning the pages of a book helps me mark my progress, and underlining prose that stands out to me makes reading a very intimate occasion. It could also be the science behind it: that regular books ease our minds into sleep. But it's likely that reading allows me to rely on a singular focus to transport me to a new world, leaving all my stresses and personal problems behind. I stop the selfish cycle of technology that centers around checking my Facebook or Instagram, or taking selfies, as I wait for my brain to get rewarded from notifications and likes. Real books allow me to step outside myself and enter someone else's world. The modern world, after all, can be tiring. Reading an old-fashioned paper book might seem out of style, wasteful, or impractical. But don’t underestimate the simplicity of holding a physical book in your hands, flipping through the pages, and not having anything else to shift your focus to. Commit to the classic paper book and you'll get the full, healthier experience. By By February 22, 2015 Frank Schembari loves books — printed books. He loves how they smell. He loves scribbling in the margins, underlining interesting sentences, folding a page corner to mark his place. Schembari is not a retiree who sips tea at Politics and Prose or some other bookstore. He is 20, a junior at American University, and paging through a thick history of Israel between classes, he is evidence of a peculiar irony of the Internet age: Digital natives prefer reading in print. “I like the feeling of it,” Schembari said, reading under natural light in a campus atrium, his smartphone next to him. “I like holding it. It’s not going off. It’s not making sounds.” Textbook makers, bookstore owners and college student surveys all say millennials still strongly prefer print for pleasure and learning, a bias that surprises reading experts given the same group’s proclivity to consume most other content digitally. A University of Washington pilot study of digital textbooks found that a quarter of students still bought print versions of e-textbooks that they were given for free. “These are people who aren’t supposed to remember what it’s like to even smell books,” said Naomi S. Baron, an American University linguist who studies digital communication. “It’s quite astounding.”. Earlier this month, Baron published “,” a book (hardcover and electronic) that examines university students’ preferences for print and explains the science of why dead-tree versions are often superior to digital., distraction is inevitable and comprehension suffers. In years of surveys, Baron asked students what they liked least about reading in print. Her favorite response: “It takes me longer because I read more carefully.” The preference for print over digital can be found at such as the Curious Iguana in downtown Frederick, Md., where owner Marlene England said millennials regularly tell her they prefer print because it’s “easier to follow stories.” Pew studies show the highest print readership rates are among those ages 18 to 29, and the same age group is still using public libraries in large numbers. It can be seen in the struggle of college textbook makers to shift their businesses to more profitable e-versions. Don Kilburn, North American president for Pearson, the largest publisher in the world and the dominant player in education, said the move to digital “doesn’t look like a revolution right now. It looks like an evolution, and it’s lumpy at best.” And it can be seen most prominently on college campuses, where students still lug backpacks stuffed with books, even as they increasingly take notes (or check Facebook) on laptops during class. At American, Cooper Nordquist, a junior studying political science, is even willing to schlep around’s 900-plus-page “Democracy in America.” “I can’t imagine reading Tocqueville or understanding him electronically,” Nordquist said in between classes while checking his e-mail. “That would just be awful.” Without having read Baron’s book, he offered reasons for his print preference that squared with her findings. The most important one to him is “building a physical map in my mind of where things are.” Researchers say readers remember the location of information simply by page and text layout — that, say, the key piece of dialogue was on that page early in the book with that one long paragraph and a smudge on the corner. Researchers think this plays a key role in comprehension. But that is more difficult on screens, primarily because the time we devote to reading online is usually spent scanning and skimming, with few places (or little time) for mental markers. Baron cites research showing readers spend a little more than one minute on Web pages, and only 16 percent of people read word-by-word. That behavior can bleed into reading patterns when trying to tackle even lengthier texts on-screen. “I don’t absorb as much,” one student told Baron. Another said, “It’s harder to keep your place online.” Another significant problem, especially for college students, is distraction. The lives of millennials are increasingly lived on screens. In her surveys, Baron writes that she found “jaw-dropping” results to the question of whether students were more likely to multitask in hard copy (1 percent) vs. Reading on-screen (90 percent). Earlier this month, while speaking to sophomores about digital behavior, Baron brought up the problem of paying close attention while studying on-screen. “You just get so distracted,” one student said. “It’s like if I finish a paragraph, I’ll go on Tumblr, and then three hours later you’re still not done with reading.” There are quirky, possibly lazy reasons many college students prefer print, too: They like renting textbooks that are already highlighted and have notes in the margins. While Nordquist called this a crapshoot, Wallis Neff, a sophomore studying journalism, said she was delighted to get a psychology textbook last year that had been “run through the mill a few times.” “It had a bunch of notes and things, explaining what this versus that was,” she said. “It was very useful.” When do students say they prefer digital? For science and math classes, whose electronic textbooks often include access to online portals that help walk them through study problems and monitor their learning. Textbook makers are pushing these “digital learning environments” to make screen learning more attractive. They prefer them for classes in which locating information quickly is key — there is no control-F in a printed book to quickly find key words. And they prefer them for cost — particularly when the price is free. The Book Industry Study Group that about a quarter of 1,600 students polled either downloaded or knew someone who downloaded pirated textbooks. Students, it turns out, are not as noble in their reading habits when they need beer money. They become knowledge thieves. But stealing texts probably is more a reflection on the spiraling cost of higher education — and the price of textbooks, up— than some secret desire of students to read digitally. If price weren’t a factor, Baron’s research shows that students overwhelmingly prefer print. Other studies show similar results. The problem, Baron writes, is that there has been where faculty and textbook makers are increasingly pushing their students to digital to help defray costs “with little thought for educational consequences.” “We need to think more carefully about students’ mounting rejection of long-form reading,” Baron writes. And that thinking shouldn’t be limited to millennials, Baron said. Around the country, school systems are buying and laptops for classroom use, promising easier textbook updates, lower costs, less back strain from heavy book bags, and more interactivity. But the potential downsides aren’t being considered, she said. “What’s happening in American education today?” she said. “That’s what I’m concerned about. What’s happening to the American mind?” When Baron started researching her book on reading, some of her colleagues responded with pity. “Did I fail to understand that technology marches on?” she writes. “That cars supplanted horses and buggies? That printing replaced handwritten manuscripts, computers replaced typewriters and digital screens were replacing books? Hadn’t I read the statistics on how many eReaders and tablets were being sold? Didn’t I see all those people reading eBooks on their mobile devices? Was I simply unable to adapt?” But after learning what millennials truly think about print, Baron concluded, “I was roundly vindicated.”. ![]() ![]() Book Description How the Immune System Works 4th Edition pdf How the Immune System Works is not a comprehensive textbook. 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It balances text and equations, allowing the physics to shine through without compromising the rigour of the math, and includes numerous problems, varying from straightforward to elaborate, so that students can be assigned some problems to build their confidence and others to stretch their minds. A Solutions Manual is available to instructors teaching from the book; access can be requested from the resources section. Related searches: Download Introduction to Electrodynamics by David J. Griffiths ebook, Introduction to Electrodynamics David J. Griffiths PDF format, Introduction to Electrodynamics by David J. Griffiths.doc download, Read Introduction to Electrodynamics by David J. Griffiths in ePub, Listen to Introduction to Electrodynamics AUDIOBOOK, Introduction to Electrodynamics David J. Griffiths azw download, Check out Introduction to Electrodynamics David J. Griffiths ePub Download, Book review Introduction to Electrodynamics David J. 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