i recently heard of a technique to for lack of a better phrase 'Supercharge' An naturally aspirated engine, with a technique called "inertia supercharging", all with proper engine blueprinting and cam timing. Anyone know of any good websites, books, etc, on how to accomplish such a feat? let me know! Thanks fellas
It's a lot of work, and even if you do it it won't be that much better. Also it pretty much has to be a 4 valve or more engine. I had a teacher at UTI tell me he got 104% volumetric effenciency out of a hyabusa engine. Jimmy
You are essentially filling the cylinder with more fuel/air mixture than it would normally fill with...i.e. increasing the volumetric efficiency. Hard to do?? Maybe...maybe not. What you have to consider is the WHOLE tract...starting with the air cleaner/entry into the carb & ending some ways down the exhaust pipes. A lot depends on your combination of parts, & how you, the engine builder, choose to make them work together. There are some things than can be done to street engines...but, by and large, street car owners can't be bothered. To be fair, pressure wave management/scavenging is harder to accomplish on a street car due to having to fabricate the exhaust around the car, vs. having a "clean slate". There are certain other techniques/parts that may not be practical on a street car (for example, some single plane intakes are very efficient & lend themselves towards increasing VE, but, it may not be a good idea to use them on the particular engine in question). So far as "not that much better" goes...again, it depends on a lot of things...also, as a general rule, you can increase VE at a certain RPM, or RPM band, but you will not necessarily see it increased over the entire RPM span of the engine. Certain NASCAR (2 valve )engines are capable of reaching 118% VE or more, albeit over a fairly narrow RPM band. Well-built drag racing engines tend to have somewhat lower VE comared to this, but generally have a wider RPM band. David Vizard is one author who has written about this...his books on cams/valvetrains & carbs/manifolds are useful to get a start on this subject. You might also want to look at his book How To Build Max Performance Chevy Small Blocks On A Budget for an overall view (regardless of your engine brand). There are some older books that are difficult to find nowadays that address it as well. Two other sources of information can be kart engine builders & motorcycle engine builders....racing kart engines depend heavily on improving VE, due to their lack of displacement.
The Chrysler long rams were originally set up for max effort at fairly low RPM for high end passenger cars; according to one test I read back when, ram effect fairly well matched kickdown of the auto trans, producing a real rush when passing. Along came the superstock era, and Chrysler's first move was a kit of instructions and template to remove a section of divider in these, shortening the isolated passages for ram effect at higher RPM. Later they released castings with walls already shortened.
good info homespun. the inertia 'supercharging' is limited to a pretty short powerband, whether it's high or low, even with variable timing and variable plenum volume. perfect example of a low rpm inertial S/C is the Tuned Port Injection from the 80's/90's IROCs/Vettes. the iron 305/350's have some pretty aweful heads but still have a wonderful low rpm torque curve because the plenum volume AND shape are "tuned" or engineered to give that ram air effect. Both Lingenfelter and TPIS have quite a bit of good material available. TPIS is mostly focused on TPI/LT1/LS1 efi but lingenfelter covers the whole gamut of designing air/fuel delivery for sbc's
It's all about plenum volume and keeping a column of air moving. When a moving mass of air/fuel hits the back of a closed intake valve, it all stops. Keep the motor revved up, keep the cam timing "aggressive" and keep the mass moving in a big container and you got yourself a recipe for "inertia supercharging." It's the principle behind long-runner intakes, like tunnel rams and those big injector stacks on Hilborns and the like. They work great within a specific RPM range assuming the cam timing, valve size, intake port and exhaust will all support it. But they don't work so well outside of their comfort zone. Real superchargers work better.
I posted this a while back. It's not mine but a good explanation of ram theory, which I think, is what you are asking about....kind of. It makes references to charts that did not make the cut and paste, so you can't see them but it should still provide some useful info. Ram Theory In addition to discovering the best use for the fig, Sir Isaac Newton created three "law's of motion". More commonly known as the "law of inertia", the first law of motion is: An object at rest tends to stay at rest and an object in motion tends to stay in motion. This law is the foundation for Ram Induction. Visualize the intake cycle of the engine as air flowing through the intake manifold runner, past the intake valve, and into the cylinder. Everything is fine and dandy until the intake valve shuts. Here is where the law of inertia comes to play -- because the air was in motion, it wants to stay in motion. But the air can't go anywhere because the valve is shut so it piles up against the valve like a chain reaction accident on the freeway. With one piece of air piling up on the next piece of air on the next on the next, the air becomes compressed. This compressed air has to go somewhere so it turns around and flows back through the intake manifold runner in the form of a pressure wave. This pressure wave bounces back and forth in the runner and if it arrives back at the intake valve when the valve opens, it is drawn into the engine. This bouncing pressure wave of air and the proper arrival time at the intake valve creates a form of supercharging. In order to create this supercharging, all of the variables have to be aligned so the pressure wave arrives at the intake valve at the right time. This combination of synchronized events is known as 'resonant conditions'. The Math for Long Rams Let's look at some numbers to see how the 30" long ram tubes were developed. Our pressure wave travels at the speed of sound. A good estimate for the speed of sound is 1,125 feet per second. For the F & G camshaft, the intake valve is open for 2680 of crank rotation. The engine rotates twice (7200) for the intake to open once. 7200 minus 2680 = 4520 of crank rotation that the intake is closed. At 2,800 RPM, 4520 = .0268 seconds. (See below) 2800 rev/minute divided by 60 seconds/minute = 46.66 rev/second 46.66 rev/second X 3600/rev = 16,8000/second 4520 / 16,8000 per second = .0268 seconds. This .0268 seconds is the critical time factor. During this .0268 seconds that the intake valve is closed, the pressure wave is moving at 1,125 feet/second and travels 30.15 feet. At resonant conditions, the pressure wave has to travel 30.15 feet to arrive at the intake valve when it is open. Since the pressure wave spends this time going up the runner AND going back down the runner, the runner length is actually only half of 30.15 feet, or 15.075 feet, which is equal to 181 inches. Swell. Terrific. 181 inches. How does a 30" ram tube work if our equations say we need 181"? The answer is: 6 Start the clock the first time the valve slams shut and the pressure wave is formed. The wave bounces away from the valve and reaches the end of the 30" tube. Time now: .00223 seconds. The wave bounces back down the 30" tube and hits the closed intake valve. Time now: .00446 seconds. The wave bounces off the valve and repeats the trip every .00446 seconds. Time Bounce .00446 sec 1 .00892 sec 2 .01338 sec 3 .01784 sec 4 .0223 sec 5 .0268 sec 6 At the critical time of .0268 seconds, our wave traveled the target distance of 181" up and down the tube. Although our pressure wave arrived at the intake valve five times to find it was still shut, on the 6th bounce our wave arrived to find the valve open. The pressure wave entered the cylinder and we had ram induction! This chart demonstrates the effect of ram induction using long rams: The example above has demonstrated why ram induction works. Now let's look at the limitations of ram induction. The following parameters affect the arrival of our pressure wave at the intake valve: Engine speed The number of crank rotation degrees the intake valve is closed. Length of the intake runner tube. If these parameters are not balanced properly, ram induction doesn't work. Let's go through the calculations again with the engine RPM changed to 1200 RPM: The critical time factor calculates to .0528 seconds. At .0528 seconds, our pressure wave has bounced around 11.8 times. In this situation, the wave is only 80% through the intake when the valve opens and the pressure wave arrives at the valve too late. Change the RPM to 3600. The critical time factor decreases to .02084 seconds. At .02084 seconds, our pressure wave is midway down the tube during its fourth bounce when the intake valve opens. Once again, the pressure is not synchronized to the open intake valve. In the illustrations above, we only changed engine speed. What would happen if you also decreased the intake runner length and adjusted the cam timing? You could once again synchronize the pressure wave to the valve opening for 3600 RPM and you would have Short rams! QUESTIONS Why wasn't ram induction use before 1960? It was. Racing engines used tuned intake and exhaust systems to boost performance. Offenhauser and Hillborne produced some exotic tuned systems. What problems did Chrysler solve to make ram induction viable for a production vehicle? First, the engineering equations had to be meshed with the realities of the real world. In the real world, the speed of the pressure wave is affected by the cross sectional shape of the intake runner, the number of turns and bends in the intake, the temperature of the under hood air, the fuel evaporation cooling from the carb, the heating by the exhaust gas bypass pipes, the surface roughness of the manifold walls, and the list goes on. It would take considerable time and effort to evaluate these factors. To expedite the ram induction development program, Chrysler built adjustable length (telescoping) ram manifolds. With adjustable rams, Chrysler could easily evaluate different configurations until they got something that worked. Reliable sources say the ram configuration that reached production was designated as "stage 5". Secondly, solving the problem of under hood packaging was a hurdle. The ram manifolds not only had to fit under the hood, they had to be reasonably easy to service, and they had to survive for the normal life expectancy of the vehicle. There were also manufacturing problems: the long aluminum castings took every bit of manufacturing expertise available at the time to overcome porosity problems. Where is Ram Induction Today? Ram Induction didn't die with the letter cars. In fact, ram induction is so common today that almost every new engine design incorporates the concept. When you look at those snake-like intake manifolds in the new 300M or the PT Cruiser or the V-10 Viper, you are looking at ram induction.
simply put: you are calculating the sine curve (harmonic frequency) of the intake charge and utilizing its characteristic of continual motion to maximize the potential fuel mixture getting into the engine at a specific range.
wow, Lucky Strike, that expands on my plenum volume/shape comment just a little bit! that's an awesome explanation, where did you get that from?! another little piece of useless knowledge I have relative to the TPI manifolds...a lot of guys that modify them will get higher flowing baseplates and runners(the tubes that curve around), which increases the volume. The effect of that is that it raises the rpm range in which the ram effect takes place. you gain mid range to high rpm power but lose low rpm (well, if you consider 800-1,500 rpm an important of your powerband!! haha) it's interesting to see a lot of the mid 90's and newer plenums because they do a lot of variable plenum volume stuff specifically for this ram effect. I remember working on a Ford Taurus SHO with a Mitsubishi?(I think...) engine. had a medusa head for an intake, with both short and long runner plenums and seperate throttle bodies to be able to have that ram effect for a much wider rpm range so it would be a useful street engine. that thing was pretty damn fast for a mid 90's family ferd sedan.
This is just plain old soup up savvy, nothing new, just that most people never thought about it this way.
And...to think about it yet another way...it goes beyond the manifolding, beyond 1959, back to the first practical applications of the Otto engine. The classic descriptions of the otto cycle describe the valve events as coinciding with pistons moving into each of the 4 strokes, so valves are described as opening and closing at TDC and BDC for their events. This did not work worth a hoot in real life due to charge inertia...just what this is about. SO...from very, very near the beginnings of our engines, valves opened and closed before and after piston events to allow the gasses to get moving and to take advantage of resisual movement...exactly the stuff that any camshaft design jacks around to maximize results at some given RPM range. The oldest reference that I have concealed at work here, nowhere near the beginning of this stuff, is a Ford of England engineering 101 text from about 1935. "this arrangement (classic otto)...is not practicable in operation...valves merely used to open and shut....and have no part in inducing those gases to start flowing..." The article then goes into gas inertia/momentum and how this relates to valve timing events and their extension past the relevant piston events. In other words, the same thinking as is used in exotic manifolding has already gone into simply making your lawnmower run.
Nothing new,and you don't need a 4 valve motor to do it. Intake runner length is optimized for a specific rpm range. Search for "ram tuning".
Thems is the alleged ringleaders...but my main point was that you couldn't build a curved dash Olds or a lawnmower without recognizing gas inertia. It intrudes even into extreme low RPM engines with flow tracts made out of pipe fittings. The Ramchargers certainly put certain ideas firmly into the popular consciouness...inertia tuning and altitude, for two.
So all I need to do is increase my volumetric efficiency?!?!?! Dude! I'm TOTALLY gonna do that to my FLATTY!
With todays electronics you can actually vary the length of the "ram" tube to provide a very wide range of tuned length. In fact the 2007 Yamaha 1000 cc crotch rocked actually has a pair of inlet stacks located one above the other and when a certain rpm is reached the top stack is raised which changes the tuned length to the length of the bottom stack. Pretty neat. Variable lenght inlets worked so well that F1 outlawed it for 2007. Rex
I read somewhere that the Ramchargers got a lot of their info on Tubing Lengths and Cone Tapers from the guys who worked with Norton Racing Bikes in England. ( Norton Racing Bike Technology was also used on the Vanwall Grand Prix Cars BTW... ) Not what this Thread is about, but the Title made me think of a type of "Supercharging" I read about some time in the late '70s ( I think...) It was a weird system with a Crank driven Drum which had a lot of Ports ( or channels ) connecting the Intake and Exhaust side. There was almost no energy used to turn the drum, because it was only spun to phase the pressure waves between the Intake and Exhaust sides. It must have been a dead end, as far as practical use goes. Because I never heard anything else about it...
isn't there some benefit also gained in those rotating air cleaners not quite the volumetric efficiency tack but relevant to us rodders/customizers in terms of more bang for your buck
Does anyone have a formula that you can input variables to decide runner length at a given RPM or RPM range? I saw one in one of the magazines a few years ago and would like to ram tune the intake runners on a bike that I want to run at the ECTA speed trials at Maxton NC. It will be a run from standing to timing at the end of one mile. It will be running at wide open throttle so the Rpm range should be easy to determine. Thanks for any help or input. Gene
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