Wave Tuning Goals

[buddy rawls]

Are you actually seeing response due to the enertial tuning in and of its self? Or are you rocking in and out of the engine's flow characteristics with respect to valve events and ramp rate? I do not know how you can determine that the enertial tuning was truly the culprit for the power gain or loss.

there will be far better gains, for the average motor hound, with correctly matched valve events.

To truly evaluate the aspects of enertial effects paired up with valve events and evaluate the true culprit for power loss and gain would take a serious lab and engineering facility.

[hotrod]

There are actually two different techniques for "tuning" intakes and exhaust. As mentioned in the above post, one technique takes advantage of the conversion of kinetic energy of the mixture velocity as it decelerates and the other takes advantage of the effects produced by the reflections of pressure waves in the intake tract ( sonic wave tuning)

The first is mostly involved with runner diameter and mixture velocity, and to some extent tube length and parasitic effects of collector lengths on exhaust headers and intake runners and plenum volumes on the intake side. Rapidly moving exhaust as it streams into an exhaust collector tends to drag exhaust gasses out of adjacent exhaust tubes, likewise, in the intake manifold mixture motion into one runner tends to help acceleate mixture moving into an adjacent runner.



The sonic tuning or wave tuning is based solely on the cam events timing, and the local speed of sound in the intake mixture or the exhaust gasses. When the intake valve first opens a negative pressure pulse begins to run up the intake runner at the local speed of sound, when it reaches the plenum it is reflected as a positive pressure pulse and runs back down the runner to the intake valve. If the intake runner is the right length this pulse or a second or third harmonic pressure pulse will arrive just as the intake valve is closing and stuff the last little bit of mixture into the cylinder and help resist reversion.

There are also sonic effects that take place inside an intake plenum as if its sized properly it "rings" at a frequency that aids or fights the sonic wave reflections in the intake runners. By "rings" I mean that pressure waves reflect back and forth inside the plenum like a wave sloshing from one end of a bathtub to the other. It in effect acts much like an organ pipe or a pop bottle as you blow across the top of it.

Likewise the enertial effects of the mixture column suddenly slowing down as the valve begins to close "stacks up" mixture at the back of the intake valve from the ram effects of the rapidly moving air slamming into the rapidly closing valve. the combined effects of these two processes can produce overpressures in the intake runner in excess of 5 psi.

I'm at work so cannot go into more detail at the moment, but if you want to see the best simplified explaination of sonic wave tuning I've ever seen, go to a library and check out the july and august 1962 hotrod magazine.

Very good article that I have yet to see improved on. In the book on scientific design of intake and exhaust systems they also have a pretty good discussion of the issues complete with the forumula that Chrysler Corporation used in its patent application for the long "ram" manifolds it put on the ramcharger engines, 413, and 392 hemi etc.

Another good book that touches on is the a book on Two cycle engine tuning but off the top of my head I cannot recall the exact title.

Short version --- it gets really complex really fast!

Larry

[BillyShope]

"jacksoni" has gone to the trouble of posting the complete Steve Magnante article from, as I recall, the July '99 issue of Hot Rod. Steve did an excellent job of explaining inertial or "water hammer" tuning.

I realize it's a long post, but, please, Larry, take the time to read it.

Many have confused the traversal of a pressure front with that which is called a "sound wave." Again, a sound wave, by definition, involves a negligible pressure difference and should not be considered when discussing intake and manifold tuning.

I believe it was in this thread that I posted a description of an exhaust system which consisted of simply a tube for each cylinder with a megaphone at the end of each tube. After reading Steve's article, you'll understand that the purpose of the megaphone was to minimize flow losses as air entered the megaphone to flow toward the closed exhaust valve and NOT to aid directly in the expulsion of the exhaust gases.

[SteveS]

There are actually two different techniques for "tuning" intakes and exhaust. As mentioned in the above post, one technique takes advantage of the conversion of kinetic energy of the mixture velocity as it decelerates and the other takes advantage of the effects produced by the reflections of pressure waves in the intake tract ( sonic wave tuning)

The first is mostly involved with runner diameter and mixture velocity, and to some extent tube length and parasitic effects of collector lengths on exhaust headers and intake runners and plenum volumes on the intake side. Rapidly moving exhaust as it streams into an exhaust collector tends to drag exhaust gasses out of adjacent exhaust tubes, likewise, in the intake manifold mixture motion into one runner tends to help acceleate mixture moving into an adjacent runner.



The sonic tuning or wave tuning is based solely on the cam events timing, and the local speed of sound in the intake mixture or the exhaust gasses. When the intake valve first opens a negative pressure pulse begins to run up the intake runner at the local speed of sound, when it reaches the plenum it is reflected as a positive pressure pulse and runs back down the runner to the intake valve. If the intake runner is the right length this pulse or a second or third harmonic pressure pulse will arrive just as the intake valve is closing and stuff the last little bit of mixture into the cylinder

The literature seems to casually mix these two different effects. From my reading, the first effect is a reult of what was posted in the lengthly article in the preceding post and is initiated at the time of intake closing. The second effect, which is described above, is initiated at intake opening and is said to be a result of a pressure differential between the chamber and the the port........the accelerating gasses creating a pressure wave. Is this correct and which of the two is more significant ?

[BillyShope]

Obviously, I'm a strong proponent of the inertial, or "water hammer," effect. I have never read or heard any valid explanation for the observed torque increases based on sonic waves. The required pressures simply aren't there! In addition, only the water hammer paradigm allows an explanation for all the torque curve "bumps" which occur with a strongly tuned engine.

[hotrod]

"jacksoni" has gone to the trouble of posting the complete Steve Magnante article from, as I recall, the July '99 issue of Hot Rod. Steve did an excellent job of explaining inertial or "water hammer" tuning.

I realize it's a long post, but, please, Larry, take the time to read it.

Perhaps you should read my references before you jump to conclusions.
I did read the article and that is the reason I made the post. I very much appreciate the effort involved in transcribing the article but, I have problems with the content of the article itself. It contains factual errors and is poorly written in my opinion, over simplifying and in some cases confusing causes and effects.

He starts off by asserting that :

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.

He then goes on to give a rather muddled description of the tuning of the arrival time of pressure waves in the pipes, repeatedly mentioning "catching the wave", "Resonant manifold tuning" (the organ pipe analogy) i.e. his assertion and his description do not match up.

His quote:

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.

This is a description of a sonic pressure pulse moving up a runner and being reflected and traveling back to the valve that initiated the pressure pulse (sound wave). This description and following paragraphs, has no reference at all to pressure recovery from the kinetic energy of a moving column of gas. It is a reasonably accurate description of what I alluded to as "sonic wave tuning" in my post.

He also miss states the gas velocities by a substantial margin when:

Traveling at close to 100 mph through the intake runner, you can imagine there is plenty of energy waiting to be released.

As we all know from other discussions on this forum ideal peak mixture velocity at max flow in a well designed head is approximately .55 mach or about 600 fps, or about 400 mph on a flow bench. Recent research shows the peak velocity in a live engine could be significantly higher. The maximum possible pressure due to suddenly slowing a 400 mph air flow is with adiabatic compression ( i.e. no loss of heat) --- 3.04166 psi).
(Source NACA report number 247)

Pressure recovery due to suddenly slowing an air stream is never perfect and you are very lucky if in practice you can get from 50% - 75% of the theoretical maximum. Ram effects have been measured well in excess of 5 psi, so the acoustic effect is at least as important as the inertial ram effect.

He states that Chryslers formula for the ram length was N x L = 84,000 where the N = the rpm, and L= length in inches. According to other sources, the actual formula used in the patent application was L= 72C/N + or - 3 inches, where C = speed of sound in the gas at the expected temperature and pressure in the intake runner.

This reduces to the above NxL=84000 formula if and only if the speed of sound in the intake runner is 1166 ft/sec.

I personally would rather have the real formula rather than a simplified formula with no explanation of its source or the information content lost due to the simplification.

He also completely ignores the scavenging effect or interaction of adjacent pipes due to either acoustic pressure wave effects or the "jet eductor" effects of a high speed flow in one pipe pulling gas flow from adjacent pipes. ( collector action on 4 to 1 and 4-2-1 headers which is an effect of the velocity of flow of the exhaust stream and choosing ideal pipe diameters)

Obviously Bill Shope was trying to simplify a very very complicated topic, which is why I listed 4 sources that are much more in depth and every bit as authoritative as his article.

I do have one correction to the sources, my memory was a little off, now that I am home here are the complete citations for the sources I mentioned.

Hot Rod Magazine -- July 1964 ( not 1962)
Gordon Blair B. Sv, PHD G.I. Mech Eng. Mexico State University.
4 page article with formulas for intake ram tuning. Includes additional technical references.

Hot Rod Magazine -- August 1964 ( not 1962)
Gordon Blair B. Sv, PHD G.I. Mech Eng. Mexico State University.
3 page article with formulas for ram tuning exhaust systems.

Tests and calculations conducted by the above author show that for a 2 psi peak suction at the intake valve at maximum piston velocity would be reflected as a 2 psi positive pressure pulse from a properly formed bell mouth inlet stack.
Formulas derived by the author produce results consistent with the Chrysler formula, but include a more refined approach.

Scientific Design of Exhaust and Intake Systems
Philip H. Smith FI Mech E MSAE
John C. Morrison BSc PhD MI Mech E


274 page book covering in great details the dynamics of the automotive intake and exhaust system with Chapter 5 pp75 - 116 devoted exclusively to pressure phenomena. Source for the above mentioned Chrysler Patent application formula. Many illustrations of actual pressure diagrams of pressures in cylinder and in the intake and exhaust tract of running test engines. Very interesting data.



Two-stroke Tuners Handbook.
Gorden Jennins

156 page book on tuning the two cycle engine with 21 pages devoted to exhaust ram tuning design, including formulas which like all the above sources focus on tuning the arrival time of a reflected pressure pulse and not pressure recovery from the enertia of a fast moving column of gas.
Gives very good illustrations and easy to read discussion. Includes design and effects the megaphone has on ram tuning.

Larry

[BillyShope]

Larry, you continue to make reference to sonic waves, which only confuses the matter.

The pressure rise due to sudden valve closure, as I indicated earlier, is equal to the product of the density, flow velocity, and sonic velocity. For a derivation of this, I would refer you to any standard fluid mechanics text which discusses water hammer. With a flow velocity of 400 mph, the pressure rise would be about 10 psi. I didn't bother to check out Steve's estimate of 100 mph for those tests, but, considering the huge diameter tubes that were used, I wouldn't be surprised if it was closer to 100 than 400. (When I saw them, I was beginning to wonder if we'd see any effects at all.)

The NL = 84000 is what you'd hear in the hallways of Chrysler Central Engineering at the time. I've never read the patent application. I'm not even certain the understanding was clear at the time of the patent application. Remember, the relationship was empirically determined, so the value of the sonic velocity...and any analysis offered in the patent application...was considered unimportant. And, should still be considered so. Common sense would seem to dictate that the "information" front should chase the last pressure front for optimum effect, but I wouldn't bet any money on it.

I would still maintain that Steve's explanation is very clear, but I'm familiar with that which he's describing. Perhaps you should read it again, being careful to omit any consideration of sonic waves. I thought his comparison to weather fronts was quite helpful.

You mention interaction with other cylinders. This greatly complicates any analysis, of course.

Peugeot had an intake manifold, quite a few years ago, that had an odd lump in it. When asked, by one of the magazine testers, the purpose of the lump, all an engineer could say was that the engine ran better with it there. I would like to see more tests run with tubes with closed ends connected perpendicular to the main passages. The effects of such closed tubes are well known to those who study water hammer, but little has been done with engine manifolding in this area.

While I was teaching a few years ago, I tried to get some student interested in doing an open channel simulation of engine manifolding (for his thesis), using flow depth of water...instead of pressure...to simulate water hammer. I think this would be a fascinating study. Unfortunately, I couldn't get anybody interested.

[OldSStroker]

I would like to see more tests run with tubes with closed ends connected perpendicular to the main passages. The effects of such closed tubes are well known to those who study water hammer, but little has been done with engine manifolding in this area.

This works well as an exhaust tuning device, and has since at least the early 60s. Don't OEMs use this principle to attenuate certain frequencies in inlet tracts? If it works to cancel frequencies can it work to amplify high pressure areas? Maybe I'm on the wrong track here, but I see a loss of total energy in the inlet runner even if the tuning added to the + pressure area near the closing valve. Net net might be a gain. Direct injection would be useful here, I think.

If you did such a thing on an FI intake, you might give new meaning to "bunch of snakes" plumbing.

[BillyShope]

I'm not aware of its use on the inlet side, OS, but I've been away from the industry for a long time. The Peugeot example would seem to indicate that gains are possible. This is something that could easily be checked out with the open channel simulator. Any engineering students out there looking for a Masters topic? Triaged?

[Ape]

Hello everyody

Hotrod reffered to two articles of g.p.blair!!

Is there somewhat a chance that´you could perhaps scan those articles in and send em?? I would be very gratefull since im allways interested in articles by g.p.blair, and from the period of time i assume it must heve been falling into the period where blair did a lot of work together with norton to develop highly succesfull race motorcycles.

anyways intersting to read the ongoin communication, about watérhammer vs. sound waves, i ve also allways been kept into believing in the theory of sound waves, but then on two strokes it´s also defintely not the sound waves on the intake. Hmm i´ll warm that topic up perhaps when im more settled on the theory.

[SteveS]

anyways intersting to read the ongoin communication, about watérhammer vs. sound waves, i ve also allways been kept into believing in the theory of sound waves, but then on two strokes it´s also defintely not the sound waves on the intake. Hmm i´ll warm that topic up perhaps when im more settled on the theory.



When you secure control over the additional theory, please share it as we are now up to four, variously supported and purported, "induction tuning effects":

1) An effect arising from the opening of the intake valve

2) An effect arising from the closing of the intake valve

3) An effect arising from maximum piston velocity on the descent and

4) The Helmholtz effect

[gofaster]

Here's a site that has more GP Blair info

http://www.profblairandassociates.com/index.html

[hotrod]

Sorry for the delay getting back to this thread, I've been working 12 hour night shifts the last few days and dealing with a major server outage at our data center so had other things on my plate.

Is there somewhat a chance that´you could perhaps scan those articles in and send em?? I would be very gratefull since im allways interested in articles by g.p.blair, and from the period of time i assume it must heve been falling into the period where blair did a lot of work together with norton to develop highly succesfull race motorcycles.

It is most certainly the same guy, he even mentions the DOHC Norton Manx engine in the article. I have good copies of these issues of Hotrod magazine and will see if I can scan them as either PDF or image files. If someone is willing to host the files PM me with contact info and maybe we can get these up were they will stay available for a while to the forum. I currently do not have a good place to host the files that can accept multiple downloads of large files.

we are now up to four, variously supported and purported, "induction tuning effects

I believe there are a couple other issues to consider in addition to the four you list. I personally think it is a mistake to assume there is only one dominant effect. I believe intake and exhaust tuning represent as in most engine building excercises a combination of effects and proper balance of them to achieve a specific end.

For example on an engine that has too much cam duration and is pushing a lot of fresh mixture out the exhaust port you may gain both BSFC improvements and power by tuning the exhaust so that a pressure pulse arrives back at the exhaust valve just before it closes and "kicks" some of that mixture back into the cylinder.

On another engine with different cam timing that has problems properly scavenging spent exhaust gases you might want to tune for exactly the opposite effect to have a suction wave arrive just as the exhaust valve is closing to help pull that hot combustion gas out of the cylinder.

Different horses for different courses sort of thing. That is probably one of the reasons none of the tuning formulas work in all cases, at some point you need to put the engine on a dyno and see what it tells you it needs / likes, and ignore the numbers.

Larry

[Ape]

Hey thank you very much for trying, to somehow scan it. it is very appreciated, since i have the books by him but none of his old articles, and i bet in any magazine they are easier readable than pages and pages of advanced math.

Hmm did some thinking, but i still have to look into literature, waterhammer really sounds like something i heard before. From what i remember thats how walter kaaden (of MZ-GP fame) got to the twostroke chamber(i know we are not talking exhausts, but for now it wont matter). He was in the garden and looked to the rain drain coming down from the roof, and noticed that the waves were reflected in the waterbarrel. Then they did some testing and on the intake side it worked too.

But wouldnt the waterhammer and the helmholtzchamber be perhaps the same if one looks aside what provokes the waves?? So i do believe in fact we are talking about same kids different names here.

1.Helmholtz
2. Organpipe (openvalve(end), closed valve(end))

[panic]

There are 2 important differences:
1. Helmholtz uses flask resonance including the total engine displacement and volume per cylinder, not simple pipe.
2. the better calculations include the compression ratio, since the flask volume varies with CR.