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Max Boost on stock RB25DET/ Hi-flowed turbo??

51jay

By 51jay,
in Engines & Forced Induction

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51jay Mentor

51jay

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OK Guys ......need some imput. R33 turbo has been hi- flowed and they reckon it's good for 25psi all day. But what can I actually run it at with the stock motor??

Got 3inch turbo back exhaust Big front mount I/C EMS Duel Sport

engine management, upgraded fuel pump and Sard fuel regulator.

I guess I need to decompress the motor to maybe 8.5:1 but until I do this whats it safe to run at. Boost control is turbosmart duel boost currently 7 and 14 psi and seems to work pretty well with no spiking.

GTS-t VSPEC Grand Master

GTS-t VSPEC

Posted
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51Jay,

While the turbo might be able to produce 25psi, I wouldn't recommend that on a stock engine, you will likely be in for a costly rebuild, plus the efficiency of the turbo at these boost levels is questionable.

The factory pistons have weak ring lands and boost over 1.2 bar can lead to major trouble. At full boost even with a high fuel pressure the stock injectors may be getting on the lean side. Also as the turbo produces more boost it will also be adding alot of heat to the intake air which will affect the amount of timing you can run. Hi-flowed turbo's can supply more air, but not as efficiently as a larger turbo.

If I were you I would go to a tuner, have it on the dyno and make sure that your injectors aren't running more than 90% duty cycle and that the timing is adjusted for the new boost level. I would also suggest forged pistons at these boost levels. With a bigger turbo you can supply more air at 1 bar than you will at almost 2bar. I don't think the advice they gave you was very good, without mentioning these other points.

See'ya :burnout:

51jay Mentor

51jay

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Thanks GTS-T V SPEC, I am aware of all the points you made and fully realise that while the turbo might make 25psi the motor definately won't. the question is what can I safely run it at down the drag strip??

GTS-t VSPEC Grand Master

GTS-t VSPEC

Posted
Posted

There is not such thing as safe, so it makes it difficult to answer. Pistons can blow on anything over 1bar, in fact most RB25DET's will have shot ring lands when you take them out. My suggestion, and I take no responsibility here is that 1.2bar would be the max boost I'd run with your current setup. I'd still recommend a dyno tune and also run octane booster while at the drags.

Hope that helps.

See'ya:burnout:

51jay Mentor

51jay

Posted
  • Author
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Thanks for that. I'm using 10% toluene at the drags.

I think i'll just leave it on 14psi hi-boost and see what difference it makes. We had a blown oil seal and got it hi-flowed for a price we couldn't refuse :P

GTS-t VSPEC Grand Master

GTS-t VSPEC

Posted
Posted

51jay,

Nothing wrong with a cheap hiflow, and at 14psi I think you should find it has quite a bit more on offer than the factory huffer. I agree it's better to play it safe with the boost, and the 10% toluene will provide a buffer against detonation.

Good luck with the new setup.

See'ya:burnout:

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