Gasoline

[MiLotus]

I have read a few articles about different ROM grades of gasoline and how lower octane fuels run cooler, and may provide just as much horsepower as high octane fuels. Would the real experts here speak there opinion? Thanks. J

[deltaf]

The octane rating of a fuel indicates its resistance to detonation. The higher the number (98 is better then 95 for eg), then the more ignition advance you can run, (within reason) gaining power along the way.
If the ignition advance characteristics are left alone and octane is lowered, all that will happen is that detonation will occur at that point. I dont see how itll run cooler...:scratcchin:
The only ways to get cooler running are IIRC, cooler denser charge, different thermostats, oil coolers.
From what i remember, the theoretical best temp for power is 85 deg(c) coolant, but it conflicts with the oils best power producing temp of 92-95 deg (c).
Hope this helps...


>> Edited by deltaf on Sunday 17th August 18:44

[MR2Mike]

The real power gains from a higher CR come from being able to run a higher CR. More advance does not necessarily give more power.

The cooler running issue stems from the fact that high octane petrol actualy burns slower than the cheap stuff, requiring more igntion advance and potentialy increasing the engine temperature. This is the reason that sticking high ocatne fuel in an engine designed to run on the floorsweepings is unlikely to net any significant gains.

[Incorrigible]

Yes, but being able to run more advance means you can run at higher revs = more power

[annodomini2]

assuming the engine can handle those higher revs and the cam profile etc is up to the job

[MGBV8]

From what i remember, the theoretical best temp for power is 85 deg(c) coolant, but it conflicts with the oils best power producing temp of 92-95 deg (c).

With the A sries engine - David Vizard reckoned 70C was best for BHP, any information on other engines?

Also assume diff oils will have diff temp ranges.

Also when an engine is about to go and high temps experienced it seams to produce more power, is it wortwhile running engine at as high temp possible, whilst keeping inlet side as cool as possible?

Paul