Turbo A/R Discussion

Went with a 1.0 A/r 6266 gen 2. Funny enough the Gen 2's are rated better at high boost pressure, but not necessarily as great for lowers vs. gen 1.

Should be fine

Check out Flawlez build. He's running a .63 A/R 6262. Everyone tried telling him it would choke up top but it doesn't. I'll tell you what his car just pulls and pulls up top. Even near 7k it just wants to freight train.

http://z31performance.com/showthread…-RWHP-540-RWTQ

^ Very nice. I'm looking for something that I can use and expand on. Who knows what the turbo might go on other than a VG down the line. Going to see how long this motor holds up - hopefully for a while.

Highly recommend swapping out that hotside. My .63 has shown 0 signs of choking at 25+ psi 545+ HP. You don't have to rev that high at all to make 600+. Mine broke 530 at 5300 RPM. I think the .68 would be perfect, maybe a .82 or .86 at most.

Also, what do you mean by "low 600s efficiently"?

Saying efficiently via turbo choice. I'll give the 1.0 a shot and go from there. They have a .84 divided if I want to switch it down the line. Think I'll be OK. Just want to get the car going already.

im using a GT35R (much older tech I think) with the divided .78 AR housing. This was streetfighters recommendation. haven't been back to the Dyno to see what it does up top, but it really slams headfirst into the rev-limiter.

Several tuner buddies told me the T4 1.06 divided would've been a better choice, but who knows.

Whatever the case, it will be a nice upgrade from what I was running.

On my PTE 6262 I opted for the .82 housing. Thing spools fast and pulls hard.

I always suggest running the largest turbine that is going to give you the flow you want, with a smallish turbine housing. The turbine is really what determines the overall response and power output of the charger, the A/R just tweaks it around the rpm range. So I'd suggest the 1.0.

Precision does a decent job of matching their turbines and compressors, but If you haven't already, I'd suggest checking out the new S300SXE lineup that BorgWarner just released. Killer turbos at really awesome prices.

I am running a 6266 gen two also. I think we have the same ISKY cams, I'm running EPR's 9.2:1 pistons and forged bottom end. I opted for the SS vband .82 housing. The thought process on the turbine housing and size, was if the 2j crowd can get 836rwhp at 29psi with a .82 housing… 600 will be easy to do and not strain the turbo.

^ There's someone I haven't seen in a while! Thanks for your guys input. I'll let you know how it turns out once I post dyno graphs in a couple weeks. I think the 1.0 with the twin scroll will do me good as I would most likely go with something .7x-.8x if it was an open/vband.

Our local turbo expert has been doing clever wheel clipping mods for the rally guys for years, and his contention is that while a/r plays a role, it only affects the spool ramp..

Basically the turbine wheel turns because of the air going into it radially (centrifugal thrust), but most of the power comes from the axial flow out the back

Likewise a turbo manufacturer told me the cross-section area of a divided 1.06 is the same as an undivided .63, give or take a hair… once you add the increase in pulse effect, it generally makes the 1.06 still perform better with less backpressure…

FlaweZ are you running a divided or open scroll? From what I've always understood that always plays a part in A/R as G-E discussed above.

I could understand running a .63 open scroll, but wouldn't understand anything lower than .8 on a divided (which is the reason why most don't even make something that small).