Originally posted by Frank@AMS
The coolant passages are used to cool the bearings on the turbo, Id
personally recommend at least running oil through those. As far as the GT30 being rated to 500HP, boost threshold on the turbo becomes far more apparent on a high liter car. For example, here at our shop we can run 30psi through the GT30R, at that point it stops making power on our 2.0 liter motors. On a Porsche motor, the T3 hotside would be way to restrictive even at 1.0bar of boost. There are just too many liters to fill will such a small cfm rating.
Frank, I also have heard of people running oil through the water passages, but these are for track cars which see sustained peak loads and boost. For a street car (like mine) which sees occassional full boost, I think I'm quite safe to leave those passages open. If I were building a car for street and track, I'd definitely run oil through those passages. Good point!
BTW, don't the K27-7200, K27-HFS & HF2 turbos run a T3 hotside?
'89 911 Turbo Cab
Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition