C20GET bottom end, +.5mm forged GM pistons with valve reliefs added, cast steel C20GET crank, ARP main studs, stock GET rods polished and shot-peened and resized with ARP bolts, stock windage tray, Z20LET MLS head gasket (sourced from the UK) with two Victor Gaskets .020-thick steel "head-savers", one above and one below the MLS gasket to reduce compression from 8.5:1 down to 8.0:1 (it also advanced the cams about 4deg... more on that later.) A stock 75K-mile Nube head was used, not even replaced the valve seals. I used the Nube intake with a custom upper plenum to remote-mount a Quad 4 throttle body. The turbo header is a cracked-up SS Autochrome Acura 4-tube I modified with a Daewoo exh flange I built. I cut off about 1" of the tubes and raised the turbo about 1", too. It uses a 40mm TiAl w.g. I don;t like the angle of the w.g, but it seems to work o.k. It has a separate dump tube that runs back into the exh about 1ft. from the turbo. A full 3" exh system runs into a 3" crossflow Flowmaster with twin exits. The turbo is a T3 (GT35)/T04E Super 60 hybrid. It uses a .82 a/r turbine housing. This was selected for drag racing and max power at high rpm. It is rather slow-spooling and doesn;t reach full boost til 4200rpm. Anytime you hit the floor it goes to 5psi, though, so it's not too bad for street driving. I run a Starion fmic that is modified for 2.5" inlet and outlet. It works extremely well. On the dyno or on the street, the manifold air temps never rise more than 15deg from the start of a run to the end of a run. The highest MAT I have ever seen was 102degF. I am running 93 octane and have only 4deg KR at peak torque from 4400-5100. I am actually adding back some timing above 5000, about 2-3deg.
I retarded the intake cam one full tooth on the gear to reduce overlap 15deg. This helped alot in the mid-range. Allowing faster spool and more power from 3500-up. I want to play with advancing the exh more (rasing the head advanced both int and exh about 4deg.) I have plenty of valve clearance with the thick gaskets, so I am not worried about that. I might switch to a 65 a/r turbine and hope to not lose much top end but gain some low to mid-range.
Well, the first time I dyno'd it last Aug I hit 307whp on 15psi. Now after some tuning I am up to 312whp on the same 15psi. I built the engine for 20+psi. After adding a plate to the top of the w.g spring, I can now adjust the w.g. for more boost. Just adding the thickness of the plate has raised the boost to 18psi. The extra boost feels like another 50hp! I'm sure it's not quite that much, but it is nearly imposible to drive now.
I am going to need either an airpump to scavenge the crankcase or I might try a simple drag racing trick
and build an exhaust scavenge with an old diverter valve welded to the exh pipe at a 45deg angle. Simple but effective. I say this b/c I am getting some serious crankcase pressure past the rings and they quit sealing when the blowby comes back up from below. You have to pull a vacuum on the crankcase when you are boosted (and even when not...).
My goal is 375-400whp on no more than 25psi. I really don;t want to build another engine. Besides, this is strictly for bragging rights... I will detune it back to 15psi for racing. I can barely hook it at that power level.
The car runs a Getrag 282 with a Spec stage 3+ clutch. It is very difficult to drive. If you don;t keep both hands on the wheel and watch the road ahead, you will run right off to the side and change lanes in a heartbeat!
The dyno graph below is for the 307whp run last Aug. I'll add the new graph as soon as the dyno shop emails it to me. The engine is alot smoother now and doesn;t have the dip from 4200-5000rpm.
