shell 96

well, here is a new question im preparing the cold/air charge pipe for my 62/71/14/ ht3b twins, i know that ats and bd use 3'' intake charge piping, they are smaller turbos in comparison to my 3b, but i can put together a 3'' charge pipe for $42 but a 3.5 or 4 will cost at least $130+ will a 3'' charge pipe work as well as a 3.5? thoughts? TIA

Casey

Tate

I think the 3" would be better than the others. Discharge on 3B's are 3", no? And the inducer on your turbo is 62mm, which is about 2.5". Going bigger creates a bigger volume that must be compressed, and I can't see it helping with flow. That being said, I think the bigger pipes look better. But function over form.

XLR8R

You're better off with the 3" diameter - that will retain the bellmouth expansion into the secondary's compressor housing.

shell 96

ya it dosent look as good but why expand then reduce even smaller

Mike Holmen

The 3b has a 3 1/2 inlet. You could always put on a increase/reducer boot and use the 3in. I'm planning using 3in on my next set-up. My current set-up uses 4in. Its all trial by error for me, I always have to try things for myself.

shell 96

you meant to say outlet correct? but what is the actual inside diameter?
TIA
Casey

Diesel Doc

3.25"

I made my coldpipe out of 2 3.5" U bends I paid $60 for both. Secondary inlet is 4" correct. IMO I wouldn't want to reduce the coldpipe coming right out of the primary it isn't much of a funnel but still a funnel.

shell 96

where did you find the 3.5 u bends?

Diesel Doc

a race shop in california that builds sandrails and the like. He makes custom headers so he keeps pipes in stock.

Dmaxcrusher

I think JEGS.com has some!!

Mike Holmen

I just buy mine at my local NAPA shop. I think they carry elbows up to 4in. They have short and long radius elbows. You can get 5in stuff from the semi truck shops.

MikeR

Go with the smaller pipe.
My 40/3B twins used to have a 4" pipe, and that volume took forever to fill. My new smaller diameter pipe keeps better velocity, and spools so much faster.

kantdrive55

We use the smaller pipe for velocity. The smaller pipe allows the air to flow quickly through. Bigger piping can reduce the responsiveness of the turbos.

shell 96

yes they do but its on a 7'' radius, too big.

shell 96

is your smaller pipe 3'' or 3.5?