Quote:
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Originally Posted by Grey Wulf
With out a cat, your gases don't expand. Other way, they are cooling.
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Thats what I meant. They are cooling, and you are gaining density because of it. In order to "get it all out" you need to open up the pipe. You loose even more velocity, but that is counter-acted against because you have a turbo. In the case of a turbocharged setup, the less (or sometimes the larger diameter) exhaust you have, the better. This is of course within reason.
Good catch on my wording!
Back to his question:
I remember reading a long time ago, on a "unmentionable" board a "certain well know member" switched his "vehicle" from a 3" catback to a 4" catback and saw something like "50hp/xxx 1/4 ET gains".
If someone looks up the "archives" on that certain "board" I bet the specifics can be found.