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

[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.

[Steve Tinker]

The engineering paper that Topless link shows us is only the input side of the internal combustion equation - even more complicated is the exhaust gas / muffler variations available. And one can definately affect the other.

Going back to the original question, it would have been so much easier for Porsche (or Mazda) to simply bolt on an inlet manifold sans Helmholtz resonator like Chris & Voilamettalic plan on doing BUT (as Topless says) a lot of clever engineers have done the calcs and come up with a resonator that fills the cylinder with a more efficient charge - and for very little money. How could the accountants complain. If the Helmholtz had cost $500 to produce, it may be a different matter.

Many years ago, we were trying to improve Manx Norton & AJS 7R motorcycle race engines to try & complete with the Japanese 2 strokes and it was quite common to replace the Amal GP carburettor inlet trumpet length to move the power band up or down the rev band. At the same time, we were changing the length and shape of the exhaust to prevent "megaphoneitis" a phenomenon where a hole appeared in the powerband and you went backwards so to speak. This was long before dyno's or ignition curves & power printouts.

I'm not saying don't try the mod - after all its not going to cost a lot and it can be reversed, but personally I must have spent hundreds of hours trying to "improve" basic physics concepts on motorcycles and cars, all designed by far cleverer engineers than me, and all I mostly got was blooded knuckles & negative results. Maybe I should have studies Mech Eng instead of Elec Eng.....

[ChrisZang]

So I finished my little DIY hi-flow intake project
I cut the original intake next to the Helmholtz resonator and replaced the part with a 45 degree silicon knee from eBay ($20) (see picture)

Results:
a) Performance gain/loss: No gain and no loss
I did 4 timed 30 to 60 runs in 3rd gear with same results before and after

b) Sound:
Not a dramatic improvement, but the orchestra that starts playing in my intake above 5,000 RPM has added at least one more Trumpet player to the mix

So overall, not bad for a few bucks