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

 

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.

 

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

 

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

 

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.

 

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

 

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.

 

where did you find the 3.5 u bends?

 

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

 

I think JEGS.com has some!!

 

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.

 

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.

 

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.

 

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

 

is your smaller pipe 3'' or 3.5?