A couple years ago mr2by4 set the CT27 horsepower record at 320whp on RACE GAS at 20 psi. The biggest issue was the turbo's inability to hold higher boost. Originally blamed on the turbo itself, the problem actually was the stock internal wastegate. It's only a 7 psi gate. So asking it to hold over 20 psi even with a boost controller is basically impossible.
I've been testing some stuff on my own car (a GT3071 rom tune combo kit actually) and decided to try something out on the CT27. I went to the hardware store and bought myself a fairly sturdy spring to help increase the strength of the wastegate. Armed with a 1/8th drill bit and a cordless drill I made a fairly clean install of the new spring.
I also made a wastegate tester from an air compressor pressure regulator so that I had a rough idea what I was getting myself into. I measured the wastegate flapper movement/position at 9 psi, and increased the tension of the new spring until I got the same position at 14 psi.
Here's a quick pic:
So I strapped it down and made some pulls. First my 93T's mods list (it's not very long)
Zen BOV
Power FC
Walbro fuel pump
550's
ATS FPR (50 psi)
ATS Rail
Greddy PE exhaust
3" downpipe
ATS 3.5" intake with K&N filter
old CM stage 1 clutch (that probably would not hold up on a drag launch)
some 93 octane pump gas in the tank, but mostly
C16 RACE GAS. I'd say about a 35% 93 octane and 65% C16
That's it. No cam gears, no cams, stock longblock, stock head gasket 130,000 miles.
So the new spring let me hold 1.7 bar (24.5 psi) pretty cleanly. And this is what I got:
RACE GAS (cuz I know someone is going to ask) Woo hoo. 350 wheel horsepower off of a bolt on CT27 turbo. You can tell I'm really putting the spurs to it to get that much power because the torque is dropping like a rock. Just FYI the ATS GT3071 out powered it by about 30 whp at this boost level.
See ya,
Aaron