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Discussion Starter #1
Hey guys i'll most likely get my downpipe fabbed up next week some time and just some questions before i go ahead and do it.

1. Is there much point in making the downpipe 3"?

2. Since my engine is out of the car i dont know what angles i should bend the down pipe at, i'm guessing its a direct 90 degree bend from the flange but should i make another 90 degree bend towards the back of the car or just get them to weld it when i get the engine in?

3. I would like to use the Internal Waste Gate port for my External Wastegate, i have the hole in the flange allready so i'm going to weld a pipe from that port to the wastegate then into the downpipe, my question is, will this be effective to do?

4. Is there a gasket between the Turbo and the down pipe flange?

Thanks for any input guys, much appreciated

Mat.
 

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I have yet to make a new down pipe, but I'm thinking 45% fittings if possible to lessen restriction. Do a search for a custom downpipe.
 

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If you are going to make -anything- 3", it should be the down pipe. It's useless to have a smaller pipe at the engine feeding into a larger pipe after it, even though lots of people do this. I'd say if you are going with a T3/T4 then yes, you'll see a nice improvement with a 3" downpipe.
 

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It sold for 275.00.....

Buy stainless pipe...not cheap (time and material)
Bend pipe......not easy (time)
Tig weld....................(time and material)

275.00 is pretty cheap actually
 

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Discussion Starter #6
That was a nice downpipe!

I might get a smaller 3" bend in this case and then get them to do the rest once the car is tuned and drivable (its going to be a noisey drive to the exhasut shop!)

I'm still concerned about using the internal wastegate hole for my external gate. The internal wastegate hole is only just before the turbine, i'm thinking the pressure difference wouldn;t be enough for the gas to flow via the wastegate when needed....

I dont know, guess its trial and error :)

Mat
 

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you do want a 3" dp.....you need to have the motor in the car before making the down pipe....it gets real busy in there when you go to fit in the wastegate....
you do not want to use the "little" hole (for the internal wastegate)....for the external wastegate...that "little" hole is why you get an external wastegate.....you need to come off of the manifold w/a hole as big as the e-wastegate....
there isnt a gasket for the down pipe....... .....s
 

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Discussion Starter #8
Ok :)

Luckily i have two flanges, one with the hole punched in and one without.

i guess the problem with making the downpipe in the car is the fact that i need to get it to an exhaust shop to do it hehe.

Thanks for the great reply
 

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I use the "little hole" for my external wastegate (delta gate). However, I enlarged it to a little over 1 inch. It works great. I can set my boost from 9 to 15 pounds without any boost creep. I'm also using a 2.5" down pipe (2-90 degrees). The turbo is a t3/t4 and I'm making around 275 hp at the wheels at 15 psi of boost. It worked will on a stock T3 turbo also.

Ths biggest restriction in the stock turbo setup is the wastegate chamber. The exhaust comes out of the turbo then onto a small chamber then has to neck back down to exit a 2 inch hole then out the down pipe. So by just changing the down pipe without changing the stock wastegate is not going to help much.
 

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Discussion Starter #10
Well i have a 35mm External Gate, i'm going to port that small hole as far as i can :)

Then a 3" DP :)

Thanks Wangsman great info (cause its what i wanna hear :p)

Mat.
 
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