95 RON fuel cylinder pressures?

[polobob]

Hi guys,

I'm working on a project at the moment involving E85, and one aspect I am looking at is its resistance to knock. Now what I really need to know is what sort of cylinder pressures will see 95 RON fuel begin to knock at? I know this is dependent on ignition timing etc. but just an idea will do.

Thanks,

Bob.

 

[Lou Scannon]

There are too many factors to boil it down to one cylinder pressure. For instance, charge motion, surface temperatures, charge temperature at intake valve closing, air/fuel ratio...

 

[romke]

there is no direct relationship between cilinder pressure and the occurrence of knock with a particular fuel, apart from the fact that above a certain pressure knock will occur. the tendency of knocking is heavily infuenced by combustion chamer design, quality of the ignition system and the phenomena already mentioned by hemi.

apart from that you should realize that not only low speed knock can occur, as is measured with the standard RON rating method, but also that high speed knock may occur - which usually can do a lot more harm since it is not easily detected by the operator of the engine. various fuels with the same RON rating may behave quite differently as far as high speed knock is concerned and therefore the sensitivity of the fuel (difference between RON and MON) should be taken into account when using an alternative type of fuel.