Quote:
Originally posted by nismo_gt
I stand corrected,but here in the UK there is a noticable difference
between standard unleaded fuel & Super unleaded.
I believe that Subaru even recommend the higher octane here for that very reason,my brother has a Prodrive Imprezza & the dyno showed
approx 5-7 bhp increase with the super unleaded !
So I guess its a case of try it & see
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Yes, that is because the Imprezza is tuned for the higher octane. When you run the lower grade petrol, the knock the ECU reads the engine knock and retards the timing, keeping the engine from blowing up and also reducing the power.
If someone builds and tunes an SR20 for higher octane petrol, such as running a JWT ECU, you
can run lower octane, but the ECU will pull out timing from the ignition map and you will make less power.
It's not the petrol that is making the power, but the tuning to take advantage of the higher octane.