years ago before fuel injection and electronic ignition when mechanical and vacuum advance distributes were used in the 70's to advance and retard timing relative to load and engine speed, cars and motorcycles were much more Susceptible to pre-ignition especially with low octane fuel. The reason was that because low octane has much less tolerance under pressure and heat (unstable) and is more likely to pre-ignite before the piston would reach TDC on its way up causing tiny dents on top of the piston making the piston ring like a bell, hence the term ping. Higher octane fuels are more tolerant of pressure and heat (more stable) due to additives to make it that way and therefore much more likely to detonate at the precise timing and spark ignition, hence run smother. There are allot of folks born in the late 80's & 90's that tell me I'm full of schnitzel but they line up to say that about allot of stuff they have no experience in. I know cause I was there to deal with regular gas either by manually retarding the timing to burn regular gas (less power) or run mid grade or premium. Now EI & EFI engines do this automatically but EFI does a better job at compensating like the B1250, however what you notice in lack of smoothness and maybe a bit less power using regular gas is not your imagination. In high compression engines 13:1 where heat and pressure is enormous like in my CRF450X, you either run premium gas or crack a piston, its that simple. However most production street legal vehicles have a compression ration of between 8:1 and 10:1 and can get by on regular or mid-grade gasoline without the use of premium, albeit not quite as smooth as premium which is what I use in all my bikes.
Topic: GAS - (WHICH octain ???? ) for 2001 - Bandit 1200 (Read 7428 times)