Define an ITB setup's signature sound

RyDeFly

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Aug 5, 2006
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Westminster, CO
Now, I have a question thats been buggin me for a while:
Exactly what makes the deliciously crisp intake noise of an ITB setup?

EXAMPLES:
First is the TVR Sagaris, with a n/a 4.0 liter inline 6 with factory ITBs.
http://www.pistonheads.tv/clip1049

Second is a Nissan Skyline 2000GT-R, n/a 2.0 liter inline 6 with factory ITBs..
http://www.youtube.com/watch?v=BU7L9OawuMI @28 seconds into the vid

Despite a 2.0 liter difference between the engines, they sound surprisingly similar (and I think the Nissan sounds even narlier...).


My Supra is currently undergoing surgery, and I'd contemplated an ITB setup before, but decided against it (daily driver). Even though I'm turbo, I'll be running the 9.2:1 n/a pistons and using the MAFT-Pro for tuning. The MAP sensor for the MAFT dashes any hope of a steady vacuum signal with ITBs anyway.

I've always been kind of dissapointed with how the 7M sounds. Although still far and away better than the JZ engines, 7Ms always seem to have messy harmonics. The engine note might be more at home emanating from a truck than a sports car... I'm hoping the 9.2 pistons will help in the sound department, as well as drivability, the main reason for use.
I'd happily trade horsepower potential in order for my supra to spew out that wondrous noise. I'd much rather have 250HP and that SOUND, than 400HP and a thrashy soundtrack. :biglaugh:

Anyways, I WANT THAT SOUND.
But is it possible without the throttle butterflies?

What if the actual culprits are the velocity stacks? Since the radius of the horn increases the open area of the runner the intake pulse would reflect from, would a stack create a sharper "bark" than a butterfly valve placed closer to the intake valve?
Has anybody ever seen/heard an engine with stacks, but a single throttle body?

Maybe I'm over thinking it. It might be something as simple as a tubular header(doubtful, though I've suspected the stock manifold adds to the mushy sound), or maybe its nothing more than the increased valve overlap that an ITB'd engine sports? (In which case my turbo dooms me.)

Any knowledge and experience you guys have would be a help.
 
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RyDeFly

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Aug 5, 2006
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Westminster, CO
Yeah, I've kept up with Jens' projects, very cool stuff. The 5M with 7M head and M3 ITBs is going to be incredible too.

But unfortunately, both his engines are naturally aspirated and *HAVE* ITBs, which my engine won't have, so his work doesn't help me too much.
 

mkIIIman089

Supramania Contributor
Mar 30, 2005
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You have a tubular manifold? They make a pretty significant difference in sound from my experience.

On another note... what an awesome road in the TVR vid!!
 

RyDeFly

New Member
Aug 5, 2006
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Westminster, CO
mkIIIman089 said:
You have a tubular manifold? They make a pretty significant difference in sound from my experience.

No, I don't have one, but fabricating is always in the cards.
Quite possible the sound I associate with 7Ms is actually the result of the stock exhaust manifold, as I mentioned before.
Anybody have links to video/sound of a 7m with tubular headers?

Another idea kicking around in my head is to make radically UN-equal length headers, to create a "boxer engine" type warble. eh?


buckshotglass said:
The turbo will always deaden the sound you are looking for.
I know the turbo will deaden the intake pulse and add certain amount of noise to the engine note, but I can't imagine it completely altering the type of noise, only the quality of it.
ITBs are incredibly loud as well (being vented directly to atmosphere), so a turbo to dampen might not be so bad....
I am assuming that a turbo would dampen all frequencies equally though; if not, and it creates a noticeable attentuation of certain ranges, then you definitely have a point.
If that ends up being my roadblock, how about a very thin-walled plenum to propagate the sound BEFORE it hits the turbo?
 

Ckanderson

Supramania Contributor
Apr 1, 1983
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sounds like your making a huge effort just to try to replicate intake noise.......

buy a e-30 m3 and be done with it.