Rb 25 Det

[R34GTT]

Hi guys;

Just wondering how much boost can a stock motor handle before shitting it self?

Cheers:D

[paulr33]

I wouldnt go above 9psi with the r34. Has a plastic compressor wheel which will get angry. the r33 will goto around 11psi but thats with a steel compressor wheel as far as i know

i could be wrong

[AutoTrust]

R33 series 1 & 1.5 have ceramic exhaust impellers series 2 have plastic r34 plastic again. The engines themselves will handle more boost, but the electronics and fuel systems will run out of legs before the engine does.

[nitemare5]

apparently the standard engine can handle around 16psi of boost before the internals are in trouble. This is from what i have read from the forums ages so i wouldn't take it as a gospel. But like autotrust said, the fuel and other support systems will be out of puff before the engine.

[R34GTT]

Sorrie guys........... I just wanted to know what the engine limits are in regards to boost pressure with standard internals. Sorrie about the turbo confusion.........

[JimX]

The engine is more sensitive to power than boost. You could run a small turbo at 18psi and give it no problems (aside from maybe the head gasket), but you might top out at 10psi with a bigger turbo, once they both start putting out around 250rwkw.

If it's the stock turbo, it will die before the engine at high boost (14psi and up). I'm currently running my T04 at 15psi, and when I get it tuned I'm going to see if it's worthwhile tuning it for 18psi. I think I might need to increase the size of the exhaust housing first.

[Sydneykid]

Hi R34GTT, boost is irrelevant, air flow makes power, boost is the measure of resistance within the engine to the airflow produced by the turbo. So as JimX said, standard internals have a power limit not a boost limit. The generally accepted number is 450 bhp (300 rwkw), whether you make up to that amount of power at 1.3 bar or 1.8 bar is basically irrelevant, as long as the tuning is good.

Tuning is far more important than boost level. A badly tuned engine at 1.1 bar will die long before a well tuned engine at 1.5 bar.

Hope that makes sense.

[R34GTT]

Thanks for the replies guys.......

I know that boost is irrelevant to power, but I keep on hearing that running high boost ie 1.6 bar is dangerous for a stock motor thats why I asked the question. Assuming the tuning is all good (no high level knocking (under 40 on the PFC H/C)) what is the max level of boost a stock motor can hold before something goes BANG!!!!!!!!!!!.

[RIPS]

Hi,

Sydney kid had explained it as well as anyone could I think.

As you are adamint about boost pressure rather than power levels try this:

Stock RB25det bottom end. Minor port work, VCT disabled and adjustable cam gears fitted, different cams, tubular exhaust manifold, Custom T4 style turbo, external wastegate, custom side mount plenim, plenty of fuel supply and good tuning, AV gas, 22lbs boost, 335rwkw in a circuit car, reliable. Rob

[51jay]

I've been running over 1bar for 18 months now usually 1 bar for street and 1.3 bar for strip and track, most I've used is 1.5bar but injectors were maxing out at that. Engine is still fine...uses absolutely nil oil between 5000K changes