Crossover is currently 3 inch, and wanna neck it down a foot before turbo to 2/2.5 stuff.

76gts T4 turbo, undivided flange

Poor choice?

 

The 3" would be the poor choice here.

 

Its already there, seems to work just fine.

 

Got any pics?

 

 

Where on that are you wanting to make it smaller?

 

The single large section on right side. Would chop it, transition down, then run a 2.5/2 Vband to work up front to turbo

 

If it was fine, you wouldn't be wanting to reduce it.

 

Long story short, caught a manhole cover with hotside and it bent/crimped a lot of the pipe after that vband. So redoing that part and figured 2.5/2 is easier to work with and route.

 

I wouldn't go to 2, maybe 2 1/4, but then again, I wouldn't do 3. I think either way, it all works, but I would think it will spool quicker with 2 1/4 -2 1/2. It's about velocity, just like a carb, bigger isn't always better, but that doesn't mean it wont work.

Depending on how long it's been together, and if you have any data logs, I would love to see some data once you change it.

 

Not sure I understand what you're wanting to do. What size of pipe do you have off the manifolds? I went 2" off manifolds to 14" of 3" and I start to see positive pressure at 1800 rpm.

 

Sounds like he is redoing the 3" pipe that connects to the pipe in the pic. The pipe in the pic is the crossover where two 2.5" pipes merge into a single 3" pipe. From there, the 3" pipe on the crossover connects to a 3" up pipe with the T4 flange.

Since he is redoing the up pipe, I think he just wants to know if there is a better size to reduce down to before the T4 flange.

IMO, if it spools fast enough as is, then leave it. If it take a little time to spool up, reduc it down to 2.5". I would leave it at 3" personally, but I'd be interested in the results.

Jon