I agree with what you are saying but the GTk650 uses the P trim (regular wheels?) so I am not sure if it would have similar efficency to the GTk550 with the STG 5 compressor wheel. Also i must consider that my headers are T4 and i think there would be a flow efficency compromise by going with a T3/T4 the adapter into the T3 inlet of the GTK as well (but i am considering it) However, I am considering trying a GTK with an adapter but i am still not sold on the benefits of their 'ceramic' BB and whether they are much more efficent than than a T4 Garrett. Consequently, I still havent written off the GT4088R turbo. I alsolooked at big shaft turbonetics but I dont need to go that way and it they will have reduced spool up (like you say) compared to the T4 GTseries Garretts.
So the trade off for me is go Turbonetics GTK with T3/T4 adaptor ( possible loss in exhaust flow efficency) compared to a T4 GT4088R. (which is suppose to be nice spooling anyways). However, one benefit with the GTKs not mentioned yet is that they are only Oil cooled (no water jacket) unlike the GT series garretts that are Oil/water cooled.
Interesting enough - we can add Tial into the picture. I was looking at their sweet SS turbine housings with V-Band on the inlet. A fabulous consideration for a TT configuration. I have a 993 twin plug with RSR rockers and need to service valves. So when I go to TwinTurbo I am highly considering going with a pair of GT28s with tial SS housings with Vband INLET and outlet. This will provide an easier access to the lower valves. And I must mention that tial has T31 turbine housings for the GTseries.
89 930 Cabrio , (soon to be for sale.)
Last edited by mic; 02-28-2007 at 08:04 AM..