ok ive seen a lot of great turbo builds on here, my Q is for you if you have a boosted (single turbo) v8 what size pipeing is your down pipe?

 

3"here

 

3" also

 

HHhhhmmm......you guys are running singles with a 3" downpipe? What size turbo (T3, T4, T6??) and what is the exhuast A/R?
What RPM does it start to spool? What rpm for full spool?

I have a 350ci planned for a split housing Holset .75 A/R build planned for the summer. I bought all 4" bends for the downpipe. The plan was dual 2.5" after the downpipe or 4" all the way to the rear. The 4" sounds better because it is less work to make.

 

The turbo I'm using has a T6 open volute turbine housing with an 1.05 AR. The turbo might be a little large for the 305, but I wanted to leave room for upgrading. The exhaust oulet is 4" and I reduced it down to 3" after the turbine. 3" was a tight squeeze between the engine and frame (and fuel line). Bigger tubing might have been possible, but I probably would've had to crush it a little at that spot.

On the highway and then punching it in drive, my setup spools at 3,000rpm and reaches 8psi at 3,500rpm.

 

That sounds pretty good. What I usually do where restrictions occur is cut the pipe to narrow it and weld in slightly over pieces (almost flat) to the sides and add round pieces to the front and rear of the pipe so the it has the same area. It isn't ideal due to the turbo exhuast swirl but I *think* it helps. That is what I am going to do with the 4" downpipe.

 

The turbo is a 62-1 trim with A/R .70 on the compressor side, 4" dia inlet & 2.75" outlet. The Turbine side is a "P" shaft with A/R .81 tangential housing, TO4 inlet and 3" V band exhaust. I don't have it in yet so I am not sure where it starts to spool