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Discussion Starter #1
Would a 2.5" DP flow the same as a 3" DP if all i'm running is a 14b or 16g?
 

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wisconsintsi said:
Would a 2.5" DP flow the same as a 3" DP if all i'm running is a 14b or 16g?




Backpressure in a turbo car is bad, the turbine wheel and the housing of the turbo is the backpressure. Anything that restricts flow out of the turbine will hurt responsiveness and ultimate flow. In every book that I have read about turbochargers say that the less back pressure the turbo puts on the motor the more horsepower you will get out of that motor. This is why you see turbo engine builders strive to get a 1:1 pound of boost to pound of exhaust pressure called crossover condition, in which tremendous power and efficency is produced as the intake pressure exceeds the exhaust pressure upstream of the turbine.

With that being said, I would like to say that a 3" downpipe will be freer flowing and have less backpressure, making it easyer for you to make power.
 

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Discussion Starter #6
Nice Nice...then im gonna get a 3" race pipe...I know the 3" race pipe cant bolt right up to my 3" thermal cat back b/c it necks down where it meets the cat...what would i have to do to make that bolt up?
 

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The 3" downpipe i bought from extreme motorsports has a 2.5" flange that's a 1/2" inch long then necks down to 3"

Bolts on just fine!

Saber!...!...!
:)
 

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Discussion Starter #9
but what about the RACE PIPE...i wanted to get a 3" race pipe from extreme but would i have to make any adjustments to my 3" thermal cat back to make it fit?
 

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Actually i bought the 3" Extreme/Thermal R&D turbo-back exhaust system with a racepipe & the racepipe slip-fits over the downpipe & tailpipe. They did all the cutting & welding beforehand so that it could have that slip-fit feature. You might have to do some cutting of your exhaust pipe if it has a flange on that end. Also don't forget to use 2 easy seal clamps for that.

However i can take some pictures of the exhaust system this weekend & email it if you wanna see what it looks like.

Peace out,
Saber!...!...!
:USA:
 

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Without some porting, you will get boost creep on a 14B/16G with a 3" exhaust. Port the wastegate passage of the turbo as well as that of the O2 housing to prevent this, or get a dump tube welded on.
 

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yes creep is a problem do the port work. (good point)
 

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nukefission said:
Without some porting, you will get boost creep on a 14B/16G with a 3" exhaust. Port the wastegate passage of the turbo as well as that of the O2 housing to prevent this, or get a dump tube welded on.
I dont get any boost creep whatsoever on my non-ported 14b with 3" exhaust.
 

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Well i can tell you all from my own experience that having a ported 2g exhaust manifold, ported 7cm turbine housing, ported O2 housing with dumptube, & a 3" turbo-back exhaust system made a shocking difference in performance & spool-up on my turbo!

Before the mods, it would take like 4 seconds for me to hit 13psi on my 14b when i was flooring it. After the mods, it hits 13psi instantly!

I paid about $2000.00 for all those parts, but the end result was well worth it. My reactions after the mods...
:eek: :D

Saber!...!...!
 

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TSi said:


I dont get any boost creep whatsoever on my non-ported 14b with 3" exhaust.
Something must be wrong... I have never seen that before. I'm curious why you dont get creep, any idea? Whats boost set to, cat/no cat, etc :)
 

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When you say port the WG area, are you just porting out around the WG flapper and gasket matching, or are you porting the flapper hole larger also? If so, how large?

And then obviously porting out the O2 housing and gasket matching.
 

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The exit area is the whole area after the flapper. When you consider that the flapper only opens about 45 degrees, you'll see why this is so important. Even more so than flapper hole. I take it out the larger of the gaskets, the 2g one, and then taper it in toward the seat. In certain key areas I even modify the gasket so it is larger. Then match the O2 housing to it. Doing just this I was able to get my creep from 22 psi to 16 psi. Enlarging the hole on the flapper got it to 15. Reshaping the entrance to the flapper got it to 14. But by the WG exit area made the most difference. No porting to the O2 other than matching the work done to the exit area.
 
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