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Who said anything about exact? I'm guessing that by "dead on using e=mc(2)" you mean "e=mc^(2)"? At the risk of sounding like an ******* (I am, don't worry... I'll own it) I just did to you what you were doing to him. I don't recall anyone stating some 9th place past the decimal accuracy. Maybe it's just me but you come off condescending about accuracy and exactness yet you can't use basic punctuation to express your thoughts to someone else so they don't have to decrypt what the hell you're trying to say.
i only point it out if someones trying to pass of their inaccuracy as being the correct way.
and i ready said i know my speling grammer, or punktuation are no best way two type, me sorrie (can you desniffer that haha)
Originally Posted by 1970camaroRS
It's a SWAG, buddy. Scientific Wild *** Guesses are done every-day to get engineers into the ballpark when experimenting to solve problems that are overly complicated or have too many variables.
too many variables? theres 2! only thing easier is x=x!
i think that jamesdem has the right method im just curious if pipe placement effects the length it needs to be. Also if SOS is calculated by temp at exit or where j is going to be or maybe averaged throughout the length.
(SPECULATION)The speed of sound would change all through out the pipe and in the resonator due to heat loss, therefore the speed of sound (and wavelength) would change. You would want to match the temperature where the pipe will be at operating temperature, ie during driving. The reduction in drone is due to the 1/4 wavelength. It goes through the pipe and reflects back and collides with the original wave at 1/2 wavelength, equaling a phase shift of 180 degrees. if you add these waves together the sum of the amplitude is zero.
in the top is a drawing of the waves. the area between the green lines is one cycle of the amplitude of the wave. the red arrow shows the shift.
thanks for explaining the wavelength thing, one more question. if the resonator was mounted much closer to the engine the SoS is faster so the wavelengths(and resonator length) would be shorter or longer? i thought shorter but your drawing seems to depict longer.nice drawing btw lol
for the guys just ballparking it 25-30inch seems best on the ones mounted towards muffler area, any guess what size on ones mounted in engine bay?
the velocity is equal tothe wavelength multiplied by the velocity. The frequency of the tone stays the same while the velocity increases, therefore the wavelength must increase. You need a longer resonator closer to the engine.
Every single part of the exhaust system contributes to where it will experience drone. Headers/manifolds, X/H-pipe, diameter/length/number of bends, and muffler/resonator/cats. All of those things effect the exhaust gas, and thusly effect where drone occurs.
That being said, the Helmholtz chamber has to be after all these things, right? Your "J-pipe" should be post-muffler, correct?
That would seem to be true........but check out the Ford Mustang thread I cited above. There are several instances of installations where the Helmholtz chambers are located in the head pipes, way ahead of the mufflers because of space limitations at the rear of the car.
It seems to be about chamber length and diameter, rather than location. Sometimes you just have to stick them where you can if you want a drone-free experience.
Here's another interesting set-up. I wish I had better pictures to share.
The exhaust comes out of the mufflers and feeds into an X-crossover and then out to the tailpipes. And we all thought that the X pipe or H pipe had to be up front. Sometimes outside the box means freedom to think for yourself.
Bringing this back from the dead because it's fascinating...
Would the distance or time between the pulses make a difference?
I ask due to the comparison of equal length headers vs old style log manifolds vs an engine like the LFX that has the exhaust manifold built into the head.
Are the differences to minute to factor in?
Hi,
Really sorry as I know this is a super old thread, and I am new to this forum.
Is there a way I could contact you aknovaman directly? I am just after some tips as I have a V8 and looking at getting a j pipe added to my exhaust.
Cheers
Leo
He is still active here. Hopefully he will tag up with you soon.
Love this topic -- it was being discussed at length (or ad nauseam) on the fox body Mustang forums about the same time novaman got the ball rolling here (2014). As my car was 5.0L Ford powered at the time, it RESONATED with me.
It's mentioned by a few others -- many (if not most) OEM mufflers have Helmholtz chambers built in. And they're specific to the power plant. If you cut open the V8, V6 or turbo 4 mufflers on the newer Mustangs, you'll see the internal construction is different for each. I put 5.0L Coyote mufflers behind the LS3 in mine. To my ear -- nice sound without being loud. And not a trace of resonance/drone anywhere.
Of course, if you have a system on your car that you like, but drone is an issue - then the 1/4 wave tubes will solve your problem and preserve the system/sound you like. FWIW, look under the hood of almost any EFI car from the last 30 years and you'll see Helmholtz chambers/quarter wave tubes attached to the air inlet piping - for exactly the same reason. To quell intake drone. Pic of my wife’s 2016 Subie Crosstrek.
Last edited by Michael Yount; Jul 16, 2022 at 08:10 AM.
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