Running a .82. The GTX3576r is a great turbo, and it really needs the .82 to let that compressor wheel do its job. The GTX compressor wheel really only is more efficient at higher pressure ratios, and at the pressure ratios it becomes efficent a .63 will be choking it slightly. The GTX will not spool faster than a standard cast wheel of the same size. In fact I found it spools even slower. Parts of the reason Garret came out with the GTX3576R is because the GTX 76mm wheel is more suited to a GT35 turbine since its ability to flow so much air at higher PRs is there. The GTX3071R is the one to get if youre looking to make lower power but quicker spool. Both GTX3582 and GTX3076 are not a good choice IMO.
I prefer to run larger ar turbine housings and play with the compressor wheel size to determine my spool/ability to make topend power. Right now I am running a PTE 5830 with .82AR.
I have tried the PTE 6235r, PTE 5830r, GTX3582R, and GTX 3576R. The GTX 3576R destroyed the 3582r in every way possible and just felt way better. The GTX wheels work really good at higher boost but I found alot more response with a standard 6 blade splitter wheel, especially at lower sub 20psi boost levels. All turbos were running .82AR and the current one is a 5830r with .82 which spools very very quickly and doesnt die up top (~450hp)
Another turbo to consider is the SPA, using a 7 blade wheel which offers very nice response. The PTE has shifted to 7 blades now IIRC as well. EFR turbos are 7 blade, along with most newer OEM Holsets. Tells you something.
This is on a 2.6L RB but I really think it would apply to the L series as well. Leave the .63 for the honda guys. Drive pressure is never a good thing on our motors and is a band aid fix for quicker spool. You want a free flowing exhaust housing/turbine wheel for your displacement and the smallest yet most efficient compressor wheel for your power goals for the ultimate package. Just remember you cont compare a 58/76mm 11 blade gtx to a 58/76 7 or 6 blade. The design is completley different and the GTX wont spool the same as say a 6 or 7 blade yet make more power from my opinion/experience.
In the end, dont expect the 11 blade GTX to work any magic on your motor, it has one purpose and that is to be efficient at HIGH boost. This is why EVO guys love them. Combined with E85 they have a potent turbo in a small package. Its also a very very quiet charger. Might be a good thing if youre into stealth. All said and done the GTX wheel design was originally made for an OE diesel application where high efficiency at high PRs and noise was a concern, keep that in mind when spending the 3k on one.
Edited by 240zdan, 14 July 2016 - 04:02 PM.