What is the tube between the air box and plenum called?

[Topless]

QUOTE=Steve Tinker]Chris - I would be carefull about removing the Helmholtz resonator - I removed mine on my Mazda Miata and immediately lost about 25% of available torque below 4000 rpm.
It sounded better but after about a week I was convinced that I was missing something driving around town - I was, about 25 lb ft of torque which I immediately regained when I reconnected the resonator (they are removable on the Mazda). I thought that they were fitted for only noise supression but an ex Mazda man on the MiataForum confirmed that after lots of testing at the factory, the engineers found the sound wave harmonics actually improved cylinder filling at low to medium revs.[/QUOTE]

Confirmed. That silly little box thingy (Helmholtz resonator) in the intake serves two purposes: Noise suppression and improved midrange torque. It is part of a "tuned intake" and removing it may leave a trough in your torque curve. Caveat, I have not done the math on this but I am betting a bright engineer in Stuttgart has.

For more info on what it is and what it does: http://www.sae.org/technical/papers/2005-01-3803

Ultimately though it is your car and you can mod it as you see fit. I am just passing on what I know about the intake resonance concept. My dad designed "tuned jet engine intakes" for Northrop and Rohr. Intake resonant frequency and acoustic standing waves were regular dinner table conversations, much to my mothers disappointment.

[Steve Tinker]

Thanks for the link Topless - your SAE paper seems to confirm my findings.
Ricardo Engineering has an enviable reputation in Europe for their state of the art engineering going back to the 1920's, probably one of the best consultants in the world....
We all want to improve on the design or efficiency of our vehicles, but sometimes the factory engineers who have access to millions of dollars worth of equipment really know what they are doing - or at least should do....
Unfortunately, the bean counters have a bigger and bigger hand in the final product.

[ChrisZang]

OK,

you guys got me thinking. So I'll first source a used intake and then try the mod.
If anyone has one lying around let me know. I'll also post in the classifieds

[Boxtaboy]

Wait a second...from what I'm reading, people are saying you lose torque from doing this mod, and so you're gonna do it anyway?!

[ChrisZang]

Originally Posted by Boxtaboy

Wait a second...from what I'm reading, people are saying you lose torque from doing this mod, and so you're gonna do it anyway?!

Yeah, if I don't try I'll never know - won't I?
But by securing a spare pipe I can go back to OEM

makes sense?

And actually I don't think that torque will suffer

[Topless]

Chris, give it a try and let us know what you find. If you can measure your results you will know for sure if power improved. 30-70 mph times work pretty well for performance testing our cars.

For those interested in more information on induction tuning, intake acoustic resonance, helmholtz properties, and how standing waves affect engine torque, this may be useful:
http://dinamoto.it/DINAMOTO/8_on-line_papers/risuonatore/risuonatore.html

[manolo]

I would love to see some data on this. I've seen AFE's dyno chart but Im skeptical.

[Gary H]

I'm sorry, but can someone spell it out to me: I can find references to Helmholtz resonators relating to noise suppression...and that's it.
Having an expanded air reservoir POST MAF/Throttle body can make a huge difference to the available torque - I had this bulbous looking cross-over pipe on my old Miata and it made a huge difference...but this is um-metered air before it gets to the throttle body.

So the Helmholtz resonator on the snorkel is there for added torque?

And there was me thinking it was ll about noise reduction and passing certain EU noise levels...