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Applying accoustical theories for combustion engine tunning ..
Applying accoustical theories for combustion engine tunning ..
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Old 8th August 2007, 04:25 AM   #1
JinMTVT is offline JinMTVT  Canada
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Default Applying accoustical theories for combustion engine tunning ..

I would like to know if anyone of us here,
as worked with accoustical knowledge, on engine tunning of intake to exhaust systems ??

I have read multiple books
( probably near 50 now ... )
On application of fluid mechanics and such to design and or tunning of engine components ,
and i have yet to see one that talks about the accoustical theory part of waves for tunning ...

they all state the obvious base that waves are created then propagated , and used for tunning ..but never do they go in the path of actually telling how to use,
how to predict and or how to tune for ..

What i am talking about here,
is using waves tunning with intake part, camshafts timing and lift, piston speed, valves, exhaust port to headers collectorts to exhaust end ....

If no one has any experience with that ,
i'd like to have help on finding how we can use the accoustical stuff to work with engines ..

i'll have to get reading my Master Handbook of Accoustics...but even there, i recall reading the basis,
but not real exemples on how waves acts and bouces and all ...

thanks for any help
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Old 8th August 2007, 07:25 AM   #2
Elvee is offline Elvee  Belgium
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Try a search like this one:
And then refine by examining the results
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Old 8th August 2007, 07:58 AM   #3
phase_accurate is online now phase_accurate
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Do an IP search for the international patent classification F02B27 described as:

"Using kinetic or wave energy of charge in induction systems, or of combustion residues in exhaust systems, for improving quantity of charge or for increasing removal of combustion residues"



Edit: Sorry the above is the European classification but this shouldn't pose any problem if you use a database where you can search after european classifications.
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Old 8th August 2007, 08:02 AM   #4
Jonathan Bright is offline Jonathan Bright  Australia
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A good point. I was obsessively interested in this in the 1960's when I wanted to spend my life designing formula One grand Prix cars. By chance the first serious book I read was by L.K.J. Setright who continued the series begun by Laurence Pomeroy (and his, Pomeroy's, father, I think). "The Grand Prix Car" by Setright ends in 1966. But in that he details exactly what you are after. He goes into the resonances and pipe length etc. This material is around and has been pretty exhaustively (if you excuse the pun) dealt with when you find the right source.
The theory leads to variable length induction manifolds i.e Mecedes sport cars of the mid 50's and then again much more recently, variable valve timing etc etc.
"It was the Springtime of the year when aunt is calling to aunt like mastodons bellowing across primeval swamps." P.G. Wodehouse.
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Old 8th August 2007, 08:33 AM   #5
Speedsmile is offline Speedsmile  Netherlands
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The fact that many books don't go into the specifics of inlet/outlet manifold tuning is probably because there is not very much to it*, is simply a matter of reflected waves at an pipe ending/expansion chamber, the speed this wave travels is fairly constant, the speed of sound, therefore the timing at which the reflected low pressure wave (in case of exhaust system) arrives at the inlet valve is only determined by the pipe length. The timing is then determined from the fact that you want an low pressure wave at the exhaust valve exactly around the time it opens.

Off-course this tuned state can theoretically hold only for one value of the engine speed, in practice this means a rpm small range.

The last argument is also the reason why intake/exhaust tuning is not always used on normal cars, besides the fact that the intake/exhaust geometry and especially length is severely limited due to space constraints. Although the more performance oriented makes like BMW, Audi etc are starting to use variable inlet geometry, but this adds just another complex part to the engine bay.
BTW, it is needless to say that in applications were engine speed is fairly constant intake/exhaust tuning is extensivly applied, like prop airplanes.

Hope to cleared some things up,
I study Automotive engineering as a master track so if you have any more questions you're welcome...

*I only talk about simple pipe length tuning, off-course there are other more complex methods, like adding Helmholtz resonators and the like.
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Old 8th August 2007, 09:05 AM   #6
OzMikeH is offline OzMikeH  Australia
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A friend of mine had a 4 cylinder engine with 4 into one tuned exhaust, at a certain distance down the pipe in the collector there was a flat plate welded into the pipe partially obstructing it. the obstruction did provide some restriction and turbulence but the idea of it was the exhaust valve opened, the pressure pulse (bang) travelled through the hot gas in the pipe, about half of the compression wave reflected off the washer, back up the pipes and off the back of the exhaust valves, hopefully just before the valve opened. The exhaust valve was supposed to open into a rarefraction right after the pulsation to help extract exhaust gas.
No idea if it worked as intended.
Apparently it was incredibly loud with these pulsations reinforcing each other. I think it would only work for a very limited rev range.

I have also heard of using temperature sensitive paint on the exhaust during a dyno run to determine the optimum length of pipe after the collector in a set of extractors. You trim it off at a hot or cold spot, not sure which. This also make an incredibly loud system.

Neither of these methods are suitable for street vehicles, these are open exhausts with no muffler.

have a look at 2 stroke racing bikes, they have a rather interesting looking expansion chamber on them

Australian made 4 litre 6 cylinder ford engines use a variable length intake manifold. with a set of butterflies in the inlet runners to change the length. I'm sure other engines use this method also.

remember with the exhaust gas temperature and composition is not air, the speed of sound will be different.
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Old 8th August 2007, 03:51 PM   #7
neutron7 is offline neutron7  Canada
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Dont forget to spend $13000 on a new battery wire, it will make your car feel more open and dynamic, and the slow speeds will be darker
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Old 8th August 2007, 04:51 PM   #8
DCPreamp is offline DCPreamp  United States
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I never thought about until now, but the air horns on the Webber carb in my ’69 Mini look just like the flaired port in my subwoofer.

I imagine there’s a lot that can be done with aftermarket parts to improve performance and tuning using acoustical modeling. However, there’s a ton of variables under the hood of a car that one doesn’t have to deal with in a listening environment. I also imagine the car manufacturers perform extensive tests and tuning to optimize performance and economy. Unlike what the conspiracy nuts will tell you, I highly doubt that there are substantial gains to be had that will not result in deficits somewhere else. Huge exhaust = noise, popping, and size limitations. Huge intake = noise, worse idle, lean running, etc. Exotic cams and variable-valve-timing = cost, complexity, poor idle, etc. With naturally aspirated engines, I think there are a lot of improvements in head design left to be done to improve volumetric efficiency. I saw an article on a cylinder head that used some sort of rotary ball-valves that greatly reduced friction, improved valve actuation speed, and improved the directionality of airflow into/out of the combustion chamber. The head was also thin and light. I haven’t seen anything about it in a long time, so it either doesn’t work, or there were issues with sealing the valves, or Detroit killed the inventor – who knows. . .
"Believers cling to the myth despite the evidence, reinterpret the myth to suit the evidence, or lie about the evidence to support the myth." "To err is human; to blame errors on external factors is even more so."
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Old 8th August 2007, 05:02 PM   #9
Speedsmile is offline Speedsmile  Netherlands
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Talking about normal cars, cost is a very big factor, and normal car manufactures (to my knowledge) usually do not get trough the trouble of optimizing an entire manifold system to a detail which is simply VERY costly to produce in series due to added production costs . Furthermore this argument is backed by the fact that interchangeability is important to, different engines are used in 2 or 3 types of one make.
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Old 8th August 2007, 09:24 PM   #10
Cal Weldon is offline Cal Weldon  Canada
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Applying accoustical theories for combustion engine tunning ..
Default Re: Applying accoustical theories for combustion engine tunning ..

Originally posted by JinMTVT
i'd like to have help on finding how we can use the accoustical stuff to work with engines ..
Nothing to do with tuning an engine but Ford did a neat thing a few years ago in their pick ups. They added a resonance chamber to the intake to make the engine sound more manly. No kidding, a chamber that does nothing more than make it sound good.
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