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

[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.....