Why not go with an 88mm? In the description on the VSR site it says the 85mm is rated at 1450hp, but that seems a little lofty. The 88 with a billet wheel should make more, I think. I picked up the 88mm billet wheel with 1.32 AR and have it on my 5.3. I don't have any comparison to the 85, but Ican say it's waaaay better than S475 was i was running last year. I dropped 1/2 second at the same boost level.

 

Your exhaust wheel is what dictates your max power. So a 96mm vs a 102mm. If the wheels are close to the same design the 102mm will win even if it's 3mm less on the compressor side. Right now the billet 85/102 is the same price as a billet 88/96mm. So the price is nice but haven't read or seen much about the vsr 85/102s. It's either this for my next build or twin billet eBay 7875s which would cost the same.

 

I think alot has to do with turbine flow. The china units just don't seem to flow what the actual GT55 103 wheels do. With out the turbine to match, going larger on the compressor just slows spool drastically and doesn't make much (if any) more power. That was the big limiting factor on the standard S400 stuff with 87/96 wheels with 88mm compressors. The exh wheel couldn't keep up...

 

Yep the 85mm wheel was said to be max you want to go with if using a 96mm wheel for the s400s. It's odd he has 88/103s an yet the he has these 85/102s.. I think these didn't do like you said good on the exhaust side so they made a better version..

I don't think these are gt55 clones they are more like a gt50. 55 would have a 111mm exhaust wheel like the on3 an vsr 94-106mm deals. As I said in the other thread I believe on3 an vsr use way different exhaust wheels. Vsr has a 10 blade count an on3 is 11 if I remember correctly.

 

Gets confusing when the sellers swap around inducer and exducer wheel sizes.

The GTX5533R (and 44) sizes are all 102's. But are often advertised as 111,112, 113 etc... Same with S400 stuff.

...but there are alot of diff GT55 models. some even have the 106/141 wheels in them.

 

Exhaust wheel is your restriction. So yes the 85/102mm with the bigger exhaust wheel would have more head room vs a s400 with the std 96mm exhaust wheel. That's why with a 96mm wheel Jose of fi an such have said a 85mm compressor is max you can really go.after that even with a larger compressor in it the exhaust flow is already maxed so it won't support the extra power that you could make from the larger compressor.

 

@ForceFed86 - didn't you measure backpressure with a VS S480 on a 4.8 or 5.3??

 

Yes, though I got different numbers at different locations. Originally tapped the #1 runner, just because there was a smog port of some sort on the factory manifold already, and it was easy to tap. Also had 4 different engine setups with different turbos along the way so its hard to recall. The runner was quite a bit higher than at the turbo houseing. I was told the turbo housing was more accurate.

I do remember seeing 1.4:1 at 20-22lbs on the 4.8 with the T6 1.32 housing VSR S480. Car would go 8.7X @ 158ish and was 3100lbs. That was also with factory manifolds and a 2" divided hotside.

 

I believe FI made the 94mm to maximize the 102 wheel in the s400 chassis. It gave a tiny bit more power over the 91mm with same turbine wheel so they released it

 

1.4 back pressure ratio isn’t considered max’s out is it? I know 1-1.2 would be better, but it wasn’t all done at 1.4?

@Suicidal Racing I would say that a China 88mm compressor is less efficient than something Jose built, hence the China 488 wouldn’t be all done as soon as a 485? I have to admit though, I’m not too fast and I think the S485 or S488 is going to be tough for me to max out with a Elgin 1840 cam. But wtf do I know (hehe). I might be making 1000 crank, but probably 50-100 less than that. I don’t think I’d be maxing out either of those turbos.

I need more cam before I need more turbo I think

 

Don't believe I was maxed out on the turbo... many have gone quicker at similar weight with the VSR S480. But I did seem to hit a choking point where more boost/rpm didn't net quicker times... If I were to guess I hit the limit (or at least was close) of RPM/power on my 2" hotside... (Id was 1.8" on 16g mild steel tubing) 1.4:1 is pretty good still IMO.

 

I’ve been 8.01 on a vsr s480/96 I switched to a forced induction s491/102 and same boost went 7.78 and just my .02 the vsr 102-103 exhaust wheels don’t seem to do nearly as well as the forced induction ones

 

No they don't work as good as joses for sure.seems the good 96mm wheels start having a bp issue in high 20 to low 30psi choke wise. I do know a members single s475 l33 went 5.0s on meth.