charcoal03silvy

iTrader: (1)

Did a bit of searching but couldn't find anything substantial. Been a while since I've been around here regularly, but I'm working on a new build. Not a truck, but i trust a lot of the tech and info given over here than a lot of the run-of-the-mill LS1 tech folks.. So anyways.

Crossover sizing. I'm working on an fbody getting a 364 and a single turbo. Shooting for around 1200 hp at the crank maximum. I've been doing a good deal of reading across the web, technical articles, looking through some literature, etc. According to several different places, 2.5" from each manifold/header to turbo flange is good for 2500 hp. Yet I see so many people doing 2.5" on a regular basis for vehicles with much lower hp goals.. My car will mostly be street driven but will see track time as well. I'm not looking for a high RPM screamer that takes a while to get into boost or is slow to spool at the tree.

So, after some rough, edumacated guesstimation and a little arithamatics... I'm looking at around 2 or 2 1/8th inch from flipped truck manifolds to T4 flange. (Price and availability may be an issue). I've talked to a few folks on this board privately about this and they seem to be on board with the smaller piping decision.

Looking for some other opinions on the subject as well as sizing for the cold side.

1CAMWNDR

iTrader: (21)

2" or 2.125" for sure. It will fit easier.
2.5" might work, but like you said, that has the potential to support twice the power you are interested in. And the smaller pipes will spool better.

Atomic

iTrader: (42)

I think most people use 2.5" because its a convenient size. 2" or 2.25" will be perfectly fine and bring the power in sooner, it just freaks a lot of people out seeing pipe that small that are used to massive NA exhausts. Keep in mind the gas in that crossover at go time is 1500F+ and under 30psi+ on a typical street setup. You can flow a **** ton of air under those conditions even with a "small" pipe.

It cracks me up when I see guys make 3" crossovers on giant turbos. All it does is make fabrication harder and bring the power in a week later.

TrickTurbo

iTrader: (12)

we use both 2.5 and 2.250.

charcoal03silvy

iTrader: (1)

If I'm correct, Faggart is running 2.25 on his car that's looooow 8's as well as other guys in that realm.

I'm going to try to fab up my own piping for this with flipped truck manifolds.. We'll see how it goes! 2.125 to T4 flange with 4" downpipe. Gotta get a tubular k-member to help with clearance plus knock off a little front end weight.

Any of you guys have experience with comp turbos? I've never really heard of them until recently and it seems I can get a ball bearing billet unit for pretty cheap comparatively.