Quote:
Originally Posted by Eddie25
... common sense will tell you shorter pipe means less restriction = les suction motor has to do to get air in.
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In this case, common sense is wrong. Or rather, it is only right in some circumstances.
If you've done research on exhaust systems, you'll have seen that the shortest, fattest exhaust pipes possible are generally not what you want on most engines. Short and fat pipes have a higher maximum flow, but at lower flow rates they don't do anything for you. Conversely, a long skinny pipe limits the maximum flow, but at lower flow rates the inertia of the moving gas in the pipe actually pulls more exhaust out of the cylinder.
The intake works the same way. Except the inertia is pushing the air into the cylinder, instead of pulling it out.
There are also more complex effects, like the resonances set up in the system of pipes. (Google "Helmholz resonator" for way too much info on the subject.) If you design the lengths of the pipes correctly, at some RPM/flow conditions, air will get packed in even more strongly by pressure waves in the intake than it would with just open air pressure.
OK, so with that all said: The typical low-restriction intake or exhaust will help flow at high flow rates--that meaning, at WOT and high RPMs. Guess where anyone driving for fuel economy hates to drive? Yes--WOT and high revs.
Stick with the stock intake, and just deal with the downshift is my take-away from all of that.
-soD