Johnv

What size downpipes are you single T70 guys running ?

Exhaust side of turbo is 3" , are people just running 3" downpipes or stepping up to 3 1/2" or even 4" ?

aim is for 550-600 RWHP.

Cheers
John

DrTurbo

iTrader: (3)

All you need is a 3" DP.

Johnv

Would there be anything to be gained stepping up to 3 1/2" , less back pressure , quicker spoll up ? more power ?

If not 3" would be soooo much easier to squeeze in there anyways

John Wilde

On kill you could be borderline with an improvement with the 3 1/2.
If you plan on keeping the 70 then stay with the 3 inch, if you think
you may go up to a 76 later do the 3 1/2.

engineermike

I was running 363 cid with a T-76 turbo and a 3" downpipe, stepping up to 3.5" for the cat-back. With no muffler, my backpressure at 18 psi boost was 34 psi.

I later built a 377 cid with the same T-76 turbo, but with a short 3.5" downpipe and no cat-back. At 18 psi boost, backpressure was only 26 psi. Most people say that low backpressure is not possible with a T-4 turbo and 350+ cid, but I guess with only 2 ft of large exhaust and efficiently designed headers, you get get there. .

Mike