Originally posted by chriskaven
BenS1,
Im sure the tuners do not configure the maps to run constantly past the knock limit.
They may run past the knock limit in extreme conditions (hot inlet temps). Engines will not last long if this is the case.
Even a small amount of knock can kill an engine very quickly and knock sensors are far from %100 accurate at detecting knock.
Knock sensors are used as a last resort to stop the engine going bang#
Regarding the octane rating, there is no way higher octane can make your car slower. Please explain?? Im sure max torque will come along and explain this one!
If this was the case then our ignition would never be retarded, which it is.
Higher Octane allows you to run more ignition advance without detonation. If your ignition is already advanced and not being retarded then the higher octane will result in less power. Why? See this link:
http://www.merkurencyclopedia.com/Fuel/fuelchem.html
Specifically paragraph 1 of the Engineering Data section, which says:
"Higher octane has a higher threshold of energy level required to start combustion, therefore there is less chance of detonation. If a engine is not detonating, higher octane WILL MAKE LESS POWER. Use the lowest octane without detonation."
So in other words, higher octane makes your fuel more difficult to ignite. The more difficult it is to ignite the fuel the less chance of detonation there is, and so the more advance you can have. But once you have advanced as far as you can then the fact that its more difficult to ignite means that it produces less power.
So, if you have a car that never detonates (And therefore retards the ignition) on 95ron fuel, then 98ron would actually make it run slower!
However all our cars DO retard the ignition (Indicating detonation) and therefore would benefit from higher octane fuel.
Cheers
Ben