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Originally Posted by nextse7en
I'm thinking of doing a ram air setup.
functional small scoop on the hood that feeds directly into the stock filter box?
I know that there are proven gains by going with some sort of ram air setup.
One member reported some level of success by simply cutting a hole under the fender where the intake resonator resides. My logic is that I could get higher pressure in the manifold with a scoop. And possibly a quicker throttle response with a dramatically shortened intake length.
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It's distinctly possible that you might see some gains at high speed, while running at high revs, and with wide-open throttle, although even this is not a cast-iron certainty.
At low speed there will be little or no ram effect, and at less than wide-open throttle any ram air-flow effect that you do achieve will be reduced.
Which is, of course, what throttles are supposed to do.
The price you pay is one of altering the resonant behaviour of the entire inlet tract. By making it shorter you raise the resonant frequency, which might possibly help at high engine revs,
except for the fact that the IRIS valve in the inlet manifold is set up to work with the original system.
Subaru claim that the IRIS valve contributes to a volumetric efficiency of over 100% for certain portions of the rev range. Once you change the inlet tract the IRIS valve will not open at the optimum time any more.
Its anyone's guess whether such a change will be for the better or worse overall - but if I had to bet, I know where I'd put my money
Pete.
p.s. If you want higher airflow at all speeds, just take the air filter out!!!