The more research I do the more I think I'd like to put a T66 in my car. At the same time I'd like to take advantage of the relatively low cost, and great performance of the Garrett GTBB series Turbos. With this in mind I've been comparing the specs on various GT turbos to the Turbonetics Q trim T66. I am basing this on a 1.00 ar T66 since I know of a couple of guys who are using it on a T66 with good results. A GT40 comes the closest, although the compressor turbine pairing in the Garrett catalog seems to use a larger turbine than the T66 with a comparable compressor.

Turbonetics T66 specs(assuming I am reading their catalog correctly)

compressor;

90mm wheel,2.58minor,3.584 major=52 trim

turbine;

78mm, 2.693 minor, 3.111 major=75 trim, 1.00ar



Garrett GT40 Ball bearing



82mm 50 trim compressor, 77mm 73 trim .94 ar turbine

or

88mm 54 trim compressor 77mm 84 trim 1.34ar turbine

QUESTIONS;

How will the first Garrett option spool compared to the T66, and how will the ultimate HP compare? (this turbo is Precision Turbo's suggestion for my goal)

or should I try to get the larger Garrett compressor with the smaller Garrett turbine (almost the same as a T66 Qtrim) ie

T66-- 90mm 52 trim compressor, 78mm 75 trim 1.00ar turbine

GT40-88mm 54 trim compressor, 77mm 73 trim .94ar turbine

Does anyone know if the dispacement recomendations in the Garrett catalog are based more heavily on compressor or turbine sizing?

Garret lists the suggested displacement for a GT35 @ 2.5L-3.2L, and a GT40 @ 3.5L-5.0L, and since a GT35/40 uses a GT40 compressor I am guessing the displacement recommendation relates more to turbine size(yes?)

I'm still thinking the 35/40 is a bit small for 550rwhp, Comments? (am I completely lost?)

Thanks, Carl

 

I am not feeling the love guys... Any one? I've talked to quite a few Aussies on this, the best out of a 35/40 that any one is aware of is 488@22psi. Anyone know where the 35/40s max efficiency is in psi? Thanks, Carl

 

i heard you can make 600rwhp @ 30psi but who knows................................ its still a new turbo in the US