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Discussion Starter #1
im turbocharged my setup consists of a t3/t4 turbo tial 38mmwastegate,runnin at 6.5psi,tuned with hondata,2.5chargepipes,2.5downpipe,3inchexhaust with 3inch muffler how much am i lookin to gain if i went from 2.5 to 3 inches in diameter?
 

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I'm not a turbo expert or anything... but in theory, having a 3 inch exhaust pipe with a 4 cyl. will defeat the perpose. Correct me if I'm wrong...


Caleb
 

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Hmmm.... that's what I thought! lol


Caleb
 

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so you're looking to swap out your 2.5" downpipe for a 3" one right?
i would leave it alone for now untill you get a bigger turbo or something.
if you go to 3" now you might experience boost creep and a tad more turbo lag (if any).
 

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Your turbo will lag less, but with less resistence comes less torque...


Caleb
 

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Discussion Starter #7
im just changine the exhaust itself only the downpipe is 2.5 im leaving that alone and my flexpipe is the stock size of whatever it is but im upgrading it to 2.5 from kteller and the 3inch exhaust will go from the flexpipe to the muffler itself and the muffler itself is 3 in diameter from kteller.
 

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I think factory pipes is 2.25", but you really might want to reconsider the 3" idea.... It's not a bad idea, in fact, it's a great idea. But around town you may suffer. Anyway, if you decide to, let me know how it turns out.


Caleb
 

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iLLeFFeKt CiViC said:
so you're looking to swap out your 2.5" downpipe for a 3" one right?
i would leave it alone for now untill you get a bigger turbo or something.
if you go to 3" now you might experience boost creep and a tad more turbo lag (if any).
if it's an internal gate it will tend to creep, but with an external it shouldn't creep much if at all, and for a turbo set up, no matter how many cylinders, the best exhaust is no exhaust. So a 3'' is great for a turbo 4 cyl. You tend to lose low end with a bigger exhaust on N/A applications but with a turbo you tend to spool faster and may actually gain low end.

you'll never know untill you dyno the first setup then switch to the 3'' and redyno and compare.
 

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^ thats what i thought...
 

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Couldn't tell you about power gains but 3" exhaust and downpipe will spool the turbo quicker I've seen 400hp made on 2.5"
 

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power can deff. be made on 2.5, there's no doubt in that, but you can get more gains out of a 3, it may not be justified to some people to spend the money to only gain (this is just a guistimate) 20 whp, but for some people that want all the power they can get, then 3'' or bigger is the way to go.
 

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Bigger is always better with turbo.

However 3'' exhausts are pretty loud if you care about that.

And btw 2.5'' exhaust is NOT good for 400 hp? what in the shit?

There are no lines to draw, but as a general rule of thumb 2.5'' is good for only about 220-240 hp or so...N/A!! DIfferent for boost
 

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I have a 2.5 inch dp into 3" and am currently running about 330hp. I went from a 2.5 all the way back and gained 60hp with the change to 2.5 to 3. also there is another local running around the dynoed 417whp with 2.5"dp to 3".
 

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im running a 2.5 inch d/p with my Apex-i N1 exhaust with no cat and i am hitting 244.9 whp and 190 ft. lbs. trq, the apex-i exhaus tisnt even 2.5 inches too.
 

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you could hit 400 whp on a full 2.5" exhaust.. but if you moved to 3 inch from that setup you might see at least 30-40 whp
 

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Mario Aloia said:
you could hit 400 whp on a full 2.5" exhaust.. but if you moved to 3 inch from that setup you might see at least 30-40 whp
you can hit more than 400. it all depends on setup.
 

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Normally, for turbo, bigger exhaust is better. No such thing as bogging it down, when turbo'd. A 3" will get you to spool quicker, but at only 6.5psi, it may not really be noticable. I went from 2.5" to 3" when I was running at around 17psi, and the difference was night and day.
The question is, at your boost level, will bigger exhaust really help a whole lot more to warrant the expense.
If you have plans to raise the boost one day, I say do it now and be ready.
 
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