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Hi guys, ive just finished supercharging my toyota 2.5 1jzgte l6 engine in my mazda rx7 and the intake is sooo loud its driving me insane! Instead of the twin turbos ive got an eaton M112 which i believe was made for a mustang. Its all running perfectly producing plenty of boost but i just cant stop the high pitch rush of air going into the s/c, even at idle when its just recirculating! Ive got a stock toyota supra air filter in line and pipework off to the inner wing and its alot better but not at all quiet! The airbox is made of ali which prob isnt ideal. The s/c got the stock bypass valve which works fine but is giving me a massive dump valve effect noise which i dont like every time i come off the power. Now the prob is i am seriously limited for room under the bonnet so a massive plastic airbox and pannel filter id out of the question. There is only about 4" of 3" ali tube between the airfilter and s/c which im assuming is the prob but i just dont have any room at all to run 3" plastic ducting all around the bonnet! Is there anything i can do to stop this noise! If i put a stupidly restrictive filter in could i damage or overheat the s/c? Maybe some kind of resinator or something? Anything but its got to be small! Would really really appreciate any sensible advice, can prob put a pic up sometime if that would help see how little room ive got. Also all you guys with 112's if you take the filter of the s/c and run the engine is yours rediculously loud?? Ow and its a new s/c and producing plenty of boost so am assuming its all good.
Thanks guys. Rich
From the sounds of it, what's happening is the result of resonance as the air is rushing in through the intake tubing on it's way to the supercharger. It may sound like an obvious statement, but that's all I can think of that would cause this high-pitched noise you're describing.
I realize you don't have much room but can you maybe try a reduced size intake tube? Maybe step down to a 2.75" or even a 2.5" dia. tube? I realize this will add some restriction to the incoming airflow, but the smaller tube diameter will have a different resonant frequency than the larger 3" tube which may eliminate the noise. Hell, I'd even suggest going to a home improvement store and buying ABS tubing and adaptors just to experiment with. They're cheap and once you find a combination that eliminates the high-pitched noise you can replace it with a more appropriate material.
Without a pic, it is difficult to give a reasoned answer.
Here is a pic of the current induction system on my N/A Supra.
The cold air feed would direct most of the noise to outside the car, and to line the inside of the air box with 10mm neoprene would help deaden the shock waves.
Hope that helps.
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