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Discussion Starter · #1 · (Edited)
Hey has anyone heard anyhting about MP's 3" stainless exhaust? it comes with the DP and it'd be nice to be able to just purchase the whole set up at once.
 

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It looks really nice. Its a full stainless setup, and its cost and durability reflect that. Compare that to the JT which is aluminized steel and a few hundred cheaper.
I just don't understand why MP woudn't offer both materials. Then they could compete for the economy exhaust and offer a superior product.
 

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Makeyousaab said:
estimate on HP gain.
That's not so much different on each car, and I'd like to see this too.
 

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i read somewhere once that unless in the really high end of the perf spectrum, there really isn't a significant advantage of having full 3" over a 3" dp/race cat with 2.5" from cat back. i forget when/where i saw this... any comments?
 

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Corky Bell discusses this in "Maximum Boost." I read it last night but already forgot exactly what he said.:roll:
 

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i read abotu this somewhere, the turbo causes so much restriction that wfter it, all you want is the exhaust gasses to flow as easily as possible, i think it was the vishnu tuning guy, he said the best theoretical exhaust after a turbo is one that got consistantly bigger until it ended, like a big horn.
 

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Well, Corky mentions the horn shape as well, but the main points he makes have to do w/ the exhaust being at 10% bigger than the intake and that the exhaust velocity needs to be at least...250 ft per second? Don't quote me on the last part as I was reading it at 1 am this morning... I had the fun job of changing one of those tb coolant hoses (the one from the block) at 10 pm last night...Second time I've changed it... Anyway...going too big is bad but I don't remember his exact formula.
 

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Discussion Starter · #12 ·
well I'm not sure why MP would make a 3" exhuast unless their other products would increase the performance enough to need the 3". I To have heard that you want a 3" to the cat, and then 2.5" to the muffler. I know you can LOOSE power if there isn't any back pressure at all, but i don't think this exhuast would really cause this to happen to much.
 

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realistically u can use either 3" or 2.5" and it wont result in a huge difference unless u r talking about removing the cat, and a big big turbo
 

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I have heard both arguments as well. I have the 3" dp with cat and the 2.5" saabsport cat-back. I have heard a lot about the relation of intake diameter to exhaust in that if the intake is only a certain size, it won't make a difference what the exhaust size is. So if you're intake is only a 2.5", anything over X amount for an exhaust won't make any gains.

Then there is the talk of cat or not cat. People will say that both ways creates more power. I say when it doubt, think of what is better for the earth, right?
 

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Makeyousaab said:
well I'm not sure why MP would make a 3" exhuast unless their other products would increase the performance enough to need the 3". I To have heard that you want a 3" to the cat, and then 2.5" to the muffler. I know you can LOOSE power if there isn't any back pressure at all, but i don't think this exhuast would really cause this to happen to much.
the turbo provides sufficient restriction.
 

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Okay, now I have the book:

BTW, Corky also isn't convinced that removing the cat is that important to a street car he says it may add at the most 2 psi of back pressure.

As far as exhaust, Bell says that you should want the exhaust gases exiting at approx 250 ft/sec. He says a simple guideline is the exhaust should be 10% larger than the turbine outlet diameter. However, he then offers a chart that relates bhp to recommended single exhaust pipe diameter. It is really odd compared to what we would all think, though. Basically, according to Corks, we wouldn't need 3 inch until we made oh, about 750 bhp! :eek: That's interesting... For 200 hp he recommends about uh, 2.15 inches?


He's got a formula for this....

Well, he wrote a book!:eek:
 

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ya i really dont know why people always think a bigger exhaust is better, we spent so much time trying to convince the N/a guys that 2.5" exhaust was going to be too big lol

o well ill stick to my 3" dp and 2.5" catback
 

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bk does corky bell give any specifics about t he shape and length of an exhaust or if there are any cats or muffler on the 2.15 inches for 200 hp?
 

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Need and want are different. I may not "need" 3inches but if it exhuasts more hot gases quicker and lowers EGT and maybe could help prevent knock then I am sold.
 
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