Wave Tuning Goals

[SteveS]

From what I have been able to read thus far on the internet, it is my understanding that the specific goals of wave tuning the induction system are to produce compression waves at the point of maximum piston velocity and at the time of valve overlap. And the goals of exhaust system tuning are to produce rarefaction waves at debated points during blowdown and at the time of valve overlap. Before I dig into Phillip Smith's book, I would like to ask the experts.....several of whom have already helped me......on their opinions as to the specific goals of wave tuning and their relative importance. I mention specific only to distinguish it from the general goal of promoting VE through enhancing intake charging and improving scavenging.

[Ape]

Well being unfortunately not an expert, but having read most of the literature (Smith, G.p.blair,..)about the topic and having it put into a rather strong running single cyl 2valve engine (32 cui and about 58hp), i will try to answer the question as good as possible. the intention is to lower at a certain rpm( Observable either with good P-I diagramms and lots of sophisticated and expensive equipment or with good simulation software) range the exhaust pressure+exhaust blwdwn thus resulting in low cylinder pressure, and having the intake wave entering just right on time. This of course in relation to cam timing and the specific rpm range for the specific intake closing point, and if possible over a broad range or perhaps depending on the application with possibly more than one pressure spike. pretty soon one notices that not just camtiming points are important(rules of thumbstyle) but also the involved timeareas for flow motion.(funny how the 2stroke guys new that allready in the 60´s). but i have to say i learned quite a lot

Anyways may i also recommend g.p.blairs excellent book about design and simulation of 4stroke engines, its pretty new and its more informative about the "whys" and how to deal with them than smiths book. unfortunately very expensive but worth every single penny.

regards

christian

[maxracesoftware]

Steve , i just finished converting PipeMax 5.0 DOS-version
to PipeMax 1.0 Windows 32-Bit version, it will calculate all your
"Tuned" Intake and Exhaust Lengths

but also the involved timeareas for flow motion.(funny how the 2stroke guys new that allready in the 60´s). but i have to say i learned quite a lot

and will do
"Time/Area" calculations included in Data results
along with Piston CFM demand @ 28" FlowBench Test Pressure

[BillyShope]

Go to the "formula to determine plenum size" thread for some of my comments on this subject. Also, see the article in the July '99 Hot Rod. (I'm the old guy in the picture.) A lot of people got "hung up" on the idea of sound waves back in the fifties and sixties and Phillips was one of them. A "wave" isn't going to do you much good. You've got to have a tube filled with compressed air when you open the valve and this means a process which is called, in fluid mechanics books, "water hammer." As the name infers, this is usually of interest in the flow of liquids, but water hammer wouldn't occur at all if water wasn't slightly compressible. Pressures involving liquids are much, MUCH higher, but the principle is exactly the same.

I think I've also made extensive comments in either hotrodder.com or hotrodders.com. Might be worth a search, if you can't find information, on the 'net or in a book, on water hammer.

[SteveS]

Always appreciate the help.

[jacksoni]

Larry- Does the windows version do anything the DOS does not do from a calculation/output point of view? Is it a lot easier to use? Ie what advantages of one over the other?

[BillyShope]

First, I'm always confusing Smith's first name with his last. I was referring to Phillip Smith.

Have a question about the simulation software: Does it pick up only the most significant harmonic or does it tell you where all the torque curve "bumps" can be expected?

The water hammer equation for determining pressure differential is:

qVc

where "q" is the density (don't know how to display a Greek rho), "V" is the flow velocity, and "c" is the sonic velocity. If you substitute appropriate values for air, you'll see that this provides a pressure consistent with that which would be necessary to provide the torque increases experienced with a tuned manifold.

[Ape]

hi folks are you talking about some shareware sorta program??
If so i would be rather interested )

about the intake waves, i have to say i read quite often allready that on us cars it seems like there is ambivalent info on the subject. It seems like there is not such a concentrated focus on intake wave tuning, but correct me if im wrong, ok the intake wave might not induce such pressure to be that much of value(of course also depending on the wave#+ caused added# dampening), but what if you cant get the exhaust suction low enough. Wouldnt that situation call for serious reverse flow, if the exhaust flow stays higher than intake psi? It seems like on modern 4stroke bike engines there is considerable effort given to getting the intake architecture right in order to even spread it(different lengths, on middle cylinders on stacks and headers) to spread the tq. One thing i notice of course that on my test bike it got really cammy because of the reduced spreading, of timing.

christian

[Ape]

Hi bill in case you ment the simulation software im referring too, as far as im concerned. No it unfortunately doesnt do any recomendations, or i just havent found that option:-) But as intakewave force also depends on wave dampening(angles diameters and the lot), one would have to doubt the mathematical model anyways. I for myself try to somehow interpret the spikes shown on the diagram, adn owrk on the side with the calculator or spreadsheets. But talking about ph.smiths book i do own it too but i would love to recommend g.p.blairs book with perhaps the optional simulation software. His interpretations on pressure indicatordiagrams are really great, and valuable, also he goes in depth into the subject of pressure tuning, with tons of diagrams. He is in motorcycle circles a well known guy famous for developing the modern 4stroke exhaust, also his professional software is being used by hans hermann.

PS: There seems to be really good simulationsoftware out by lotus engineering, available for free dwonloads for single cylinders

[BillyShope]

I was involved with a drag car that had both intake and exhaust tuning. It was the C/A "High & Mighty" of the Ramchargers (late fifties, early sixties). The exhaust was simply 8 tubes with megaphones at the end. The intake used a plenum with 2 4bbls. As far as I'm concerned, the exhaust tuning was a complete waste of time. (Except for the psychological effect. We were noisier than the AA/FD's!) All the exhaust did was give us a torque curve "hole" right at the launch rpm, meaning the driver tended to either bog or go up in smoke. (A group at Daimler-Chrysler is presently building a duplicate of that original car and some of us old timers are trying to talk them into somehow improving the exhaust without sacrificing the appearance.)

Some of the header manufacturers even include features which obviously act to reduce tuning effects.

For some reason...and I can't really explain it...the intake tuning depressions aren't as severe as I would expect. Everything's pretty much plus, plus.

[Ape]

Oh my gosh where you in involved with that group of chrysler students campaigning the akward looking ramcharger, werent you folks also the ones that developed the wedge fromulas for intake lenght. I think i herad about that group. Are we talking about the same thing, since i know only one car that independent "megaphone" exhausts. Hmmm the independent headers didnt do anything??? Anyways let me know if it was you folks that where on the cover of hot rod with the riveted sheetmetal ramcharger with rubber hoses.
great pioneership

regards

christian

[BillyShope]

Don't know if I'm anxious to admit to all that, but, if you've got pictures, I guess I'll have to.

The tuned intake equation was empirically derived by those involved with the development of the production manifolds, not the Ramchargers. Some of the Ramcharger members were, however, directly involved with that development. Some, but not all, were part time students at the Chrysler Institute of Engineering (now defunct). All were Chrysler employees.

[Ape]

Hey i found the site about the rebuilding of the real thing, funny how that Ram tunnel thing is still alive. Did you guys calculate back then allready the paramaters of the diameter (friction diameter etc) or was it just the length calculation?? Hmm thought about what you said about the exhausts, and they should have worked from what i think, maybe the primaries where too long, taking into consideration how short mine are(32-35") with i assume similar (65ic@0.040)camtiming. hum hum hum, wasnt that a hemi?? wonder because architecture is really similar to my engine besides slight cui mismatch. where you guys running with hemis or welded up dual squish, is that actually something considered on carhemis??? Where the intakes straight as for high rpm appl. or biased for swirl?? It must have been such a pioneerfeeling back then. did oyu guys work out the equations for the plenum by yourself working out from helmholtz theories?? by hte way short story: you know helmholtz was from over here and worked out his resonance theory in a monestery in upper austria, with claycups of certain dimensions to get the resonance outta the room while the monks where singing chorals.

[BillyShope]

Didn't know they had a URL. I'll have to look for it.

Again, we were merely utilizing the information gained by those involved with the ram manifold project.

It was a 354 with 392 hemi heads.

Again, we're not concerned with sound waves, so noise cancellation techniques are not employed.

[jacksoni]

Here is the above mentioned Hot Rod Article








Mark Hot Rod, July 1999 v52 i7 p74
RAMMING THE RAT: A Funny Thing Happened on the Way to the Dyno. Steve Magnante.
Abstract: Resonant manifold tuning, also known as ram tuning, of an automobile engine can increase torque. An experiment, using different lengths ram tubes is described. Ram tuning began to be used in automobile racing in the 1950s, and is based on the idea that it is possible to use the inertia produced by an air/fuel mix.

Full Text: COPYRIGHT 1999 EMAP-USA

Free horsepower. What a great idea. In the case of resonant manifold tuning, most commonly known as ram tuning, an engine can actually realize additional horsepower and torque simply by catching the wave. We wanted to see what effect different length ram tubes would have on horsepower and torque output. To explore this phenomenon, we plopped a Hilborn/Electromotive EFI setup on a freshfrom-the-crate GM Performance Parts ZZ 502/502 big-block and strapped it to the Superflow dyno at John Baechtel's Westech Performance Group. To help decipher the data, we asked Bill Shope, a founding member of Chrysler's legendary Ramchargers factory drag-racing team and an expert on the subject of ram tuning, to be our guide.

What Is Ram Tuning?

Ram tuning surfaced in the racing community during the early 1950s. The idea is both simple and quite complicated, depending on how deep you dig. On the surface, ram tuning simply takes advantage of the inertia contained within a moving column of air/fuel mixture as it comes to a stop against the closed intake valve. Traveling at close to 100 mph through the intake runner, you can imagine there is plenty of energy waiting to be released. By adjusting the length of the intake runners, this energy can be used to improve cylinder filling when the valve opens again. The more pent-up energy waiting to crash the gate, the more air to pack the chamber. But there's much more to it than this.

It all begins at the piston. After expelling spent combustion gases through the open exhaust valve during the exhaust stroke, the piston reaches TDC. At approximately the time the piston begins its journey back down the cylinder during the intake stroke, the intake valve opens and suction draws in a fresh air/fuel charge through the intake tract. By the time the piston reaches BDC, the intake valve is closing, and it is here that we can begin our examination of the occurrences along the length of the intake tract. For these few milliseconds, we aren't concerned about what is happening inside the cylinder or the combustion chamber. Our attention is focused on the column of air that exists between the back of the closed intake valve and the opening of the ram tube or, on a carbureted engine, the entrance to the plenum directly below the carburetor.

The instant the intake valve closes, it initiates a chain of events within that column of air. A set of four of these events will always occur in a particular order. These four events constitute a harmonic cycle. Each event involves a change in the pressure and velocity of the air/fuel mixture in the tube. These changes always begin at one end of the tube (either the closed valve or the open end) and progress to the other end. This progression, or traversal, occurs at the speed of sound; a harmonic cycle consists of four traversals.

The first traversal is the result of the fuel mixture adjacent to the valve coming to a sudden stop. As it does, it builds up a pressure which is equal to the product of the air density, the air velocity, and the sonic velocity. As the incoming molecules of air hit this pocket of air that is already stopped, they also stop, and the volume of stalled air grows in size, creating a division between the two zones; this "front" is like a weather front on the evening news. The front separates regions that are at different pressures. This front moves away from the valve and toward the open end of the tube at sonic velocity. It is the front between the two regions that traverses the tube at the speed of sound, not a portion of the air/fuel mixture itself. Each wave actually moves through the air without being of it.

When the front reaches the open end of the tube, the molecules of air nearest the open end begin to flow away from the opening of the tube. This volume of zeropressure air flowing away from the engine then extends toward the closed valve at the speed of sound, constituting the second traversal, where the air in the tube is at zero pressure and negative flow. Then, the air at the closed valve experiences a negative pressure equal in magnitude to the positive pressure initially developed when the valve first closed, thus initiating the third traversal which also travels away from the engine. Once the front reaches the end of the tube, the air inside is entirely stagnant, and at the negative pressure, air once again begins to flow into the open end of the tube. This represents the beginning of the fourth traversal, where all the air in the tube is at zero pressure and has a positive velocity traveling toward the engine.

With this fourth traversal, one harmonic cycle is completed, although it's difficult to imagine all of this taking place in the short timespan between valve closure and valve opening. The beginning of the first cycle of the next harmonic occurs when this flow region reaches the closed valve, and, again the pressure rise is equal to the product of the density of the charge, the velocity of the charge, and the speed of sound, which - at 60 degrees F - is equal to 13,420 inches per second! Shope divulged that tests conducted at Chrysler in the mid-'50s concluded that the most effective time to open the valve was after the third harmonic - the intake valve is opened just as the pressure rise begins to occur at the valve head after the 12th traversal. These experiments also showed that when tuning for the fourth harmonic, the intake runner had to be too short and couldn't contain enough air/fuel mixture to completely charge the cylinder. And efforts to tune for the second harmonic resuited in extremely long runners and the acceleration of an excessive air/fuel mass, so the third harmonic was the most advantageous.

Chrysler testing resulted in a formula to calculate where the ram effect will come into play. To wit: N x L = 84,000, where N represents the desired engine rpm to tune for and L is the length in inches from the opening of the ram tube to the valve head. Shope explains: "Let's say you're running at Bonneville with an engine that develops peak horsepower at 8,400 rpm and want to tune for maximum ram effect at that level. Then, L should equal 10 inches, as in 8,400x10 inches = 84,000." To achieve ram tuning at 5,500 rpm, simply divide the constant, 84,000 by 5,500 rpm. The result of 84,000-5,500 = 15.27, the ideal distance for the intake tract as measured from the opening of the ram tube to the valve head.

The effects of ram tuning reveal themselves as blips in the horsepower and torque curves which can either be tailored (by manipulating runner length) to coincide with, and enhance, the power peak or to bolster some other area of the power curve. In other words, just because a given engine may make maximum horsepower at 7,000 rpm doesn't mean you have to utilize the benefit of ram tuning at that speed. In fact, in most cases, you wouldn't. A drag-race engine, for instance, would have its intake system tuned for a speed a bit above the midpoint of the engine-speed range. Is ram tuning responsible for where peak torque and horsepower are made? Well, it can shift the peaks a few rpm, but the more dominant contributors are found elsewhere (camshaft, compression ratio, and so on). But there is no doubt ram tuning can be a useful tool for enhancing the power curves.

The Engine

In upcoming issues, we'll feature our 1963 Nova "The Wilshire Shaker," a street-legal replica of a mid-'60s altered-wheelbase match-race Funny Car. And what better powerplant to totally capture the "run what ya' brung" vibe than this Hilborn-injected Rat? But unlike the Hilborn-injection setups of yore, modern units are completely adaptable to EFI. By incorporating an Electromotive Total Engine Control (TEC) ignition and fuel-management system, our Nova will have street manners that match its power output.

The object of port fuel injection is to eliminate flow restrictions caused by the nozzles and venturis present in a carburetor and to optimize mixture distribution between the cylinders - fuel sprays into the individual ports, enabling equal flow. But the hassle associated with a constant-flow mechanical-fuel-injection setup on the street centers on fuel metering. Typically, the fuel pump is driven at a direct ratio to engine speed. The fuel pressure rises with speed and feeds more fuel to supply the greater demand of the engine as rpm ascends. Despite the use of metering valves and bypass circuits, it is virtually impossible to obtain optimum performance over a wide range of engine speeds. If you adjust for best power at the top end, the mixture will be lean at the bottom end and vice versa.

The Electromotive TEC-II system adapts easily to the Hilborn 396-C-8LEL EFI-specific intake manifold (2 7/16-inch-diameter throttle bores) to provide accurate fuel metering for any driving condition. A complement of sensors (TPS, MAP, [0.sub.2], CTS, IAT); eight 55lb/hr injectors (specified for this particular application); and a powerful computer which utilizes a direct-fire, distributorless, crank-triggered ignition system and phase-sequential injector firing. No, the Southern match-race stocker boys never tuned their motors with a laptop PC, but they never dreamed of running on the street either. We're nuts, though. The work is based around a GM Performance Parts 502 (PN 12371171) which was checked for proper bearing clearances before commencing a grueling 30-pull dyne party.

The Test

Dyno runs were first made with runner lengths of 19 1/2 inches - the distance from the intake-valve head to the bellmouth of the ram tube, which we achieved with the standard 12-inch stacks and the Hilborn throttle-body casting. Shope soon discovered that the calculated engine speed for the appearance of the blip on the torque curve didn't match the dyne-pull results. A comment by test-assistant Steve Abruzzese as to the possible effect of intake duration, caused Shope to remember that Chrysler's testing was done with comparatively mild camshaft events, while the cam in the 502 is a hotter 224 degrees duration at 0.050-inch lift and is a fast-acting roller to boot. For this engine, Shope calculated that a better formula would be NxL = 80,300.

After a 30-minute break-in, Baechtel let 'er rip. The best of three pulls yielded 518.1 hp at 5,000 rpm and 602.3 lb-ft of torque at 3,500 rpm. Compare that to a stock carbureted ZZ502 (502 hp at 5,200 rpm and 567 lb-ft at 4,200 rpm), and it is clear that the Hilborn/Electromotive EFI unleashed a wall of bottom-end torque and a respectable dollop of horsepower as well. And just as Shope had predicted, there's a blip in the torque curve which reflects the increased cylinder filling brought on by the harmonic tuning (see "Proof of the Pudding"). Shope also calculated that the ram effect was good for a whopping 3psi boost in intake-charge pressure at 4,800 rpm. That's close to the output of some small blowers - and it's free!

We made more pulls to test the efficiency of different runner lengths and achieved this by shortening the Hilborn tubes in 2-inch increments. With 17 1/2-inch runners, we gained 5 hp and 10 lb-ft, producing 528.3 hp at 5,400 rpm and 607.2 lb-ft at 3,700 rpm. Trimming more inches from the tubes reduced total runner length to 15 1/2 inches; horsepower and torque fell off slightly to 525.1 hp at 5,500 rpm/604.3 lb-ft at 4,000 rpm. We also tested the naked throttle-body casting (no tubes), resulting in a runner length of only 9 inches. This placed the third harmonic tuning speed at 8,900 rpm, well above our redline. Output diminished to 508.8 hp at 5,500 rpm and 547.1 lb-ft at 4,200 rpm, indicating the effect of turbulence which will form just inside the throttle body when the bell-mouth entry is absent. This turbulence reduces pressure, the flow area, and power.

As the sample tune-speed graph indicates (see "Proof of the Pudding"), agreement between calculated speeds and observed blips is quite good. Still, this procedure is not an exact science. No two dyno runs are exactly the same, and the general slope of the torque curve can cause the peak of the blip to occur at a different engine speed than that calculated by the equation. Regardless, ram tuning is very real. If you have any doubts, check out the intake manifold of practically any engine designed during the last 15 years. From the Ford 5.0 to the Chevy TPI to the Dodge Magnum, you'll see tuned runners - a sure sign that Detroit is quite hip to the lure of free horsepower and torque.

Sources

Camp Cams

Dept. HR07, 3406 Democrat Rd., Memphis, TN 38118, 904/258-6174

Edelbrock

Dept. HR07, 2700