I have a t3/t04e turbo with a 5 bolt housing, and I'm trying to figure out what size downpipe and exhaust I need. I am hoping for 300 hp at 11-12 psi.

The turbine housing outlet is 2 1/4". I'm thinking I'll need a 2.5" downpipe, 2.5" to 3" transition flexpipe, and 3" exhaust. Is this correct, or should I change something?

Thanks for helping a turbo newb

 

You've got it right. If you have room, may as well just get a 3" dp right away though.

 

yea, go full 3" the first time, save money and time

 

Ok, I'm confused. Why would I need a 3" downpipe when the turbo outlet is only 2 1/4"?

 

It all sorta comes down to dense are being heavy air. If you let your hot are expland abit in a 3" downpipe it's alot "easier" for the engine/turbo to push it out. If you were to leave it as say a 2 1/4 pipe it would be alot thicker or heavier and make alot more backpressure as hte engine cant move it quick enough. Hope that makes sense

 

So are all turbo outlets the same size, and most people just use 3" downpipes? That seems like alot of pipe for that small of a outlet hole.

BTW, thanks for the above explanation, it makes sense to me

 

Outlets can be all different sizes. It's tough to say what most people use. 2/5" and 3" is fairly common. My downpipe on an 18g has about 5 inchs of 2" pipe then 2.5" the rest. Thats the biggest I could manage with my setup unless I replace the crossmember.

Most honda's dont have much rom to work with. The best best would be to buy some cheap plastic pipe or even cradboard rolls or somehting and mock up a pipe as big as you want or need, then get a shop to weld one up for you if you don't have the means to do it yourself.

Dan

 

I will be replacing the stock crossmember with aftermarket traction bars, so I don't think fitment of a larger pipe will be an issue. I think I will go with the 3" dp