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The mkiv Supra Owners Club

Whats the best size decats for bpu


Paul372
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performance wise you probably wont notice much difference, as a huge amount of back pressure will be limited by the smallest part because of the bottle neck effect, so have a 2.5" system it won't matter if you have a 2.5 or 3" decat.

 

noise will be the biggest factor changed. if you want more noise for 3".

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yes obviously exhaust system will be most important factor, but if using the same exhaust system and comparing 2.5 or 3" decats, the 3" will make the same system louder.

 

if you put 2.5" decats on your drager system it would probably make it quieter wouldnt it?

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yes obviously exhaust system will be most important factor, but if using the same exhaust system and comparing 2.5 or 3" decats, the 3" will make the same system louder.

 

if you put 2.5" decats on your drager system it would probably make it quieter wouldnt it?

 

I don't know what the difference would be if any, isn't the difference in sound level really from removing

the cats rather than whether it's 2.5" or 3" ?

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If a restrictor ring is being used on a J-Spec, then I can't imagine there's much, if anything at all, to be gained by using 3" decat pipes over 2.5".

 

Re. noise, I use 3" decats with a Tanabe Medalion Touring system and its hardly any louder than the stock system - it just sounds deeper.

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also i would expect a 2.5 too a 3" to be louder then a 3" straight through, my thinking is its like a trumpit that way going smaller to larger just like a mega phone its also proven in the exhuast db register

http://mkivsupra.net/vbb/showthread.php?217156-Exhaust-dB-register&highlight=exhaust

 

notice how the 3" decats are louder then the 4" decats with a 4" exhuast

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