I may upgrade my k26/T04E hybrid to a full on garrett setup since I'll probably be rolling my own manifold wise... Not going to make any decisions just yet as I want to get the motor in the car first and decide what to do from there!
Marc, just to clarify the details, the only thing K26 about your turbo is the housing, everything else is T3 Stage 3, honestly there wouldn't be any advantage to going with a T3 exh. housing as well, unless you'd like to use some of the other Garrett offerings out there, there really isn't a big performance consideration over your standard T3/T4.
The new GT series of turbos are probably the most advanced line of turbos on the planet (for consumer use), they feature dual ball bearings, advanced and efficient turbine and compressor wheel and housing designs, some even inlcude aerodynamic features on the compressor housing to increase efficiency. In fact, I talked to a Garrett engineer at SEMA, he claimed the consumer GT30R they sell is identical to what the R8's run except that it features water cooling and a slightly sturdier turbine housing, performance is identical he claims. Of course, the R8's were running them 4 years ago.
The GT40 compressor that Justin refers to is quire hefty, that's a big compressor and is going to have quite a bit of lag, but will prove to be a very powerful turbo. Of course, putting the GT40 wheel in a T04 compressor housing should help, but I have no idea how it should perform. For example, some turbo builders put the K27 compressor wheel in a K26 housing, etc. General rule of thumb turbo design frowns on this kind of compressor housing swapping, but the proof is in the pudding I suppose.
Frankly, the best thing about the GT series turbos is the dual ball bearing center section, I installed a GT30 on a customer car recenly, I could get the compressor to spin by just blowing on it, it freewheels for about 20 seconds after the car is shut off...pretty crazy, but its a $1300 turbo.
Same specs as turbo I listed. 24psi, 2.0 honda 16v
Also, I found some more info on the fact the the GT wheels ARE more important then the ball bearing CHRA. This quote is from rod short of Precision Turbo:
"From what I've read, a ball bearing turbo will spool anywhere from 400 to 800 rpm quicker than a standard center section. There may be more to it, though. When you spin the wheel with your finger, the blades really turn quickly.
Garrett has told us at their engineering meetings that the ball bearing CHRA's are not as important as the GT Technology wheels are, which makes sense. It's the action of the exhaust energy on the blades of the wheel which gets everything going. With computational fluid design and 5-axis CNC machining, they've been able to come up with design(s) that increase the surface area which, in turn, makes for a quicker spooling turbo even without the ball bearing CHRA.
In the case of the GT35R, you get the new GT Technology aerodynamics with the dual bb center section.
Believe me, this turbo isn't for everybody, but we're happy to be able to offer it for those who want it."
Justin, agreed, the GT compressor and turbine blades are very advanced, and a huge progression from the T series for sure. I'd be interested to hear what a Garrett engineer thought, however, about taking one of those carefully designed compressor housings, pulling out the wheel, and retrotiffing it into a completely different housing.