Originally Posted By: MalfunctionProne
As mentioned, Octane measure is resistance to detonation. The more it has (93 vs 87, or 94 octane if Sunoco Ultra 94 or whatever) then the more resistant it is to detonation.
I think we need to talk about how that "stops knocking and pinging." I think there is some confusion there.
It also may yield more power in a higher comoression engine, IIRC. We should talk about that, too.
I think what the OP may be getting at is that some do believe that premium gas is better at "burning off carbon deposits" and that perhaps this was done by a higher temperature?
Some also DO believe that they get better fuel economy on oremium gas. Why? Because of a ... "slower burn?" ..
A modern, intuitive ECU can adjust fuelling and, importantly, ignition timing to optimise the combustion. It is possible to see gains in new cars with 'intelligent' mapping as the ECU can advance the ignition to a point just before it knocks (as detected by knock sensors). Advanced ignition timing leads to a more efficient combustion cycle (to a point) because less of the combustion time is spent whilst the piston is still rising at the end of the compression stroke (effectively slowing it down).
Equally, plenty of cars for the last few decades have had knock sensors and the ability to retard ignition if knocking occurs, protecting the engine from lower octane fuel (and other sub-optimal conditions, such as lugging the engine). If an engine's 'base' ignition timing is quite advanced, for high octane fuel, and you run it on lower octane fuel then switching back to higher octane should improve matters.
As mentioned, Octane measure is resistance to detonation. The more it has (93 vs 87, or 94 octane if Sunoco Ultra 94 or whatever) then the more resistant it is to detonation.
I think we need to talk about how that "stops knocking and pinging." I think there is some confusion there.
It also may yield more power in a higher comoression engine, IIRC. We should talk about that, too.
I think what the OP may be getting at is that some do believe that premium gas is better at "burning off carbon deposits" and that perhaps this was done by a higher temperature?
Some also DO believe that they get better fuel economy on oremium gas. Why? Because of a ... "slower burn?" ..
A modern, intuitive ECU can adjust fuelling and, importantly, ignition timing to optimise the combustion. It is possible to see gains in new cars with 'intelligent' mapping as the ECU can advance the ignition to a point just before it knocks (as detected by knock sensors). Advanced ignition timing leads to a more efficient combustion cycle (to a point) because less of the combustion time is spent whilst the piston is still rising at the end of the compression stroke (effectively slowing it down).
Equally, plenty of cars for the last few decades have had knock sensors and the ability to retard ignition if knocking occurs, protecting the engine from lower octane fuel (and other sub-optimal conditions, such as lugging the engine). If an engine's 'base' ignition timing is quite advanced, for high octane fuel, and you run it on lower octane fuel then switching back to higher octane should improve matters.