Destro

Okay, let me start by saying I abandoned this thread the last time, because it was threatened with moving to the S2000 Talk section, being a product discussion. So let's be clear; I'm not asking "which intake do u like best" or anything of a product comparison nature.

What I'm after is some thoughts on intake design theory in general. To be 100% clear on my motives, I'm planning on making some molds to lay up myself. So, this is a technical theory discussion, not a product discussion. Anyway:

There has been a recent move among many intake designers to include large volume plenum chambers between the filter and the throttle body (e.g., Gruppe M, ASM, J's). Now, traditional Helmholtz tuning suggests that a longer tube leading to the plenum will reduce the tuning peak (i.e., the rpm at which the 'supercharge' occurs). It is on this premise (I believe) that AEM produces long intake tubes, which move the tuning peak down the RPM range, and result in a torque boost at lower RPM.

So, shortening the effective length of the intake tube should raise the tuning peak, shouldn't it? I would have thought that would be a bad thing, since it would seem (from some rough calculations) to be pretty high in the first place. What am I missing?

P.S.,

Clearly, all that nice, open volume will act like a subwoofer, and it probably sounds great. But that's not what we're after here, is it?

dmw16

Now I am now tuning expert, but I do have a degree in aerospace engineering and I have done a little reading on Helmholtz tuning. I think a few things.

1) The performance gains, if any, would be miniscule
2) There is almost no way you could really analyze and control the shape of your intake to get any gains even if gains were possible

So the conclusion that I come to is that the odd shape intakes are mostly for show/marketing and not for performance gains.

This might be worth reading http://www.phys.unsw.edu.au/jw/Helmholtz.html

mic_crispy

I think AEM makes intakes with long tubes in order to get the colder air closer to the ground...

Destro

Thanks for the reply!

I'm glad you're an engineer- I don't have to worry about dumbing this down...

I agree that predicting the actual performance gains would take a lot more work that I'm willing to put into it! Predicting the frequencies of the tuning peaks is not as difficult as it sounds, though, if you can make some assumptions (as always in engineering). Particularly, that you have a system of discrete, connected volumes for which you can calculate the equivalent inductance and capacitance (so-called, because the first models were analog LC circuits). Capacitance in this case has to do with the volume of the intake runners, plenum, cylinder at TDC etc. Inductance for any tube goes as the definite integral of dx/A(x) over the length x=0..L. This type of analysis was fist published in:

Engelman, H. W.

jasonjm

Variable intake runners + fully exposed direct pathway to high-moderate pressurized air outside is the best case scenario.

negcamber

I thought the chamber was to hold an extra charge of air which would allow faster throttle response when suddenly opening the throttle.

I never made it all the way through engineering school as an undergrad, but did take a fluid dynamics class (and stayed at a Holiday Inn Express last night ). Considering the Comptech (rest in peace) CAI, the way I would envision the flow would be:

Laminar flow enters the chamber and due to the volume increase, the flow becomes turbulent filling the outer diameter of the chamber with vortexes. These vortexes create a rankin body, which allows the core flow to remain laminar from entry to exit. This state remains as long as the manifold pressure is steady. If the throttle is suddenly opened wider, the drop in pressure pulls the stored air in the outer diameter of the chamber. This allows faster response since the air does not have to travel the full length of the plenum to reach the combustion chamber.

Anyway...I'll go back to playing Dilbert.

wazzurp

S2kpuddydad or whatever his name his I think this is it, fabricated some sort of intake thingy that made 6 whp throughout the entire powerband I beleive, maybe he can chime in on his experiences.

Destro

Sounds like a pre-2006 F1 car.

s2krey

interesting.

iDomN8U

It look liked a OEM box but out of metal instead of PVC (if I recall his sig correctly)

I have a manufacturing plant at my disposal that I would like to recreate his setup and maybe even pay royalties if it works as he claims.

The fastest/biggest way to increase the HP would be to reduce the temperatue first, then design will definately help but I believe it wont be anything significant.

Unless you have a larger cc engine, then increasing the radius and design will have a greater effect.