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theres no need to add it with normal optimax, it will achieve zero. the stock ecu wont add more timing because you've added in octane booster. in fact the stock ecu has no concept of how much octane your fuel is, it simply looks at the knock sensor and if its see's detonation, assumes you are running crap fuel and drops timing and richens itself up. so in summary its pointless and achieves zero.

sorry thats assuming you are using stock ecu still, which i dont think you are?

even with an aftermarket ecu it wont gain any more power, you could advance the timing a little but you'd be better off tuning and running optimax extreme all the time.

try a tank of optimax extreme and dial in 2 more degs timing, it should be ok

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Yeh i run an aftermarket computer. My concern is that I have on the odd occasion noticed a very slight rattle on 25-26psi, running optimax

We cant get the optimax extreme hear yet unfortunately otherwise i would run it for sure.

How much timing roughly should an rb25 with gt3540 and 8.5:1 comp run on 25psi? At the moment its on about 20 degrees. it has std cams and cam gears.

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well if you can hear rattling, then its likely to be detonation.

what ecu are u using? just take out some timing on the load point where you hear it knocking/detonating. its just as case of a few load points are a bit too advanced, retard them a tiny bit

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