barkster

Greetings, fellow rice burners...

I don't own a Honda/Acura, but I was pointed this direction by one who knows engines much better than I to get some expert advice on tuned intakes. He said GT-R/ITR guys were the best at it.

I drive an MX-6 and my question came from the fact that stock MX-6's (and Probes) have a Variable Resonance Intake System (VRIS) that "tunes" the intake manifold by changing its effective length at certain RPMs through a pair of shutter valves and bypass tubes. The theory being a tuned intake, much like a tuned exhaust, will improve power. In that way, the VRIS acts like a (very) mini super charger and there is a small but noticable boost during acceleration at 3250 and 4250 RPMs.

Well, I want to add a CAI, but I'm looking for advice on tuned intakes because I don't want to counteract the "tuning" being done by the VRIS. Else, I'd like to disable it all together, and build a precision tuned air intake to get the most from it and the intake manifold.

Is there someone here who can (is willing to) explain, in the most nauseating detail (go ahead, I'm an engineer) some of the principles behind DESIGNING a tuned intake?

Thanks,
Glenn

shifty35

It's pretty simple (ha ha). Basically, your intake pipe is a closed resonator - that is, it has a resonant frequency which depents on length. You tune the length to a specific engine RPM so that subsequent air "pulses" are arriving at the valves right when they open. If you really wanted a tuned CAI, buy an AEM V2. It's tuned to 2 frequencies using 2 diameter pipes in order to maximize power in the lower RPM range as well as the upper.

barkster

Roger on the V2... I've seen it. But the VRIS already "tunes" the intake manifold to 4 different RPM bands, kinda making the 2-tuned feature of the V2 redundant and maybe even detrimental. I'm curious to know if changing the air intake (to anything other than stock) will dork that VRIS "tuning" up and counteract any of the benefits of a CAI.

... and although I do appreciate your response, I already understand what a tuned intake is and (fundamentally) how it works. What I'm looking for are any principles and simple rules or equations that I could use in designing a tuned custom intake to make the most of my existing IM and VRIS. (Or, perhaps, to know with certainty that the V2 is tuned by design specifically for my engine.)

Thanks, again.
Glenn

shifty35

Sounds like maybe the best idea would be to replace the piping after the last butterfly valve with a hard pipe the same length and an open element filter. That would give the the increased airflow capacity of a CAI without disturbing the existing system.

96gsintegra

i may be wrong but here goes... i was under the impression that a tuned intake mani changes the lenghts of its runners. why would the addition of a coold air intake change the way it would function? unless of copurse the cai and mani were tuned for diffrent rpm. then i would say just go with a "regular" cai...

s1ngle

From what it sounds like, this is a pretty cool system to begin with. Never heard of it before, and i'd definitely like to learn more. I would recommend, for now, not messing with the length of your intake by adding a Cold Air pipe. i'd say just add an open element filter, and leave it at that. otherwise you might end up with more loss than gain.