Intercooler Restricting Power Over 250rwkw On R34 Gtt

[gtst25]

Hi Bass I had the same problem with your turbo just like Grepin one of the first guys here to run this turbo. You can increase the pre load on the actuator rod but at the end of the day I always had the same problem - boost dropped to 16 psi at about 5000rpm. I adjusted that actuator to the point just before you couldn't control boost.

You can get a 19 psi actuator from gcg the hks ones are 1 bar standard. I was thinking about doing it but lost interest in the end. We tested the one on your car with the air compressor and it opens at one bar like it should. Grepin ended up buying a .86 exhaust housing but it made no difference mind you grepin was making over 312 rwkw. I had 260. Interestingly we ran the same 1/4 times. What sort of boost control do you have? The PFC one won't help as it doesn't bleed off air it's just a electric valve that opens and closes very quickly. I believe the eboost ones are the go but pretty pricey.

Nice power figure hope you're enjoying it.

[joeyjoejoejuniorshabadoo]

fwiw i have the hks actuator that come with the turbo and it holds to within 1 psi @ up to 21psi

and i have ony ever seen a 40 knock once (limiter in 3rd)

[gtst25]

fwiw i have the hks actuator that come with the turbo and it holds to within 1 psi @ up to 21psi

and i have ony ever seen a 40 knock once (limiter in 3rd)

Are you just running the hks actuator and no boost controller? If you're running a boost controller what type are you running?

[joeyjoejoejuniorshabadoo]

blitz DSBC spec s

[gtst25]

blitz DSBC spec s

If it bleeds air off from the wastegate line then it's probably a better controller than the pfc ones. That might be all bass needs I'm not sure what boost controller he's running.

[joeyjoejoejuniorshabadoo]

bass's car was making boost on the hot side and not on the cold tho.... i'm guessing there was a boost leak and that it was sealed up when the piping was replaced te last time

[SS8_Gohan]

bass/hamish - are you guys running the .63 rear housing?

hamish, your one only drops 1psi through to redline yeah?

[joeyjoejoejuniorshabadoo]

mine is the .68

set to 19psi and trails off to 18 by 7100 redline

[hypergear]

I thought I mention it. The other thing that with boost drop could be the compressor is out of puff assume the turbine housing is big enough. Which is probably why you don't really see boost dropping issues when running big turbochargers.

I've noticed that on few SR20s who's running ATR28G3 and G4 turbos that developed a issue which the stock rubber intake pipe gets sucked shut over certain boost range. So boost rise to 18psi and drops back to around 15psi. this issue gets solved once a metal intake is fitted.

For most people who's experiencing "boost dropping" issues on RB25s are mostly with smaller turbochargers running on 60mm and 71mm comp wheels. which really do make me think back to the above situation which the compressor is not be able to supply enough air to actually support above 20psi to a 6cyc engine at high RPMs.

I think this matter would be in the turbo design, The compressor of the turbo needs to be large enough to flow the right amount of air to support its application with the right turbine to dispatch compressor flow. This really leads me to think some of the early HKS turbos are not made as a very balanced setup or is not engineered to produce high boost efficiency on the RB25det.

[joeyjoejoejuniorshabadoo]

in theory that is possible, but the issue at hand was not a boost drop, but boost dissapearing between the hot and cold sides of the intake piping.

therefore it could have only been a leak, as the compressed air HAS to go somewhare, it cant just vanish.

also incorrect sompressor sizing cant be the case, as the turbo in question has been tested time and time and time again on RB25's with near identical results across the boad...