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Old 04-15-2009, 09:36 PM   #7 (permalink)
Master EcoModder
Join Date: Nov 2008
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The warm air is causing your engine to be more knock prevalent.

The colder air was allowing your engine to run on lower octane at the same spark location(roughly) without incurring knock(detonation in the cylinder as the gases expand and heat after the spark begins traveling towards the opposite side of the cylinder). In that sense the 88 octane would have helped as well as its slightly more capable of being at the higher compression or timing than 87.

Trying to replicate those results on 87 fuel is inadviseable. What your engine is doing is relieving stress in the engine by doing any number of things to reduce pressure in the cylinder at the cost of FE.

If you trick your engine into not doing that it will knock/detonate/ping more often and then you are probably shortening your engine's lifetime while also putting it within range of death on a particularly bad day. For instance lets say you are in a hurry for once and are accelerating kind of hard and your engine is experience knock because you tricked the sensors into not opening valves slightly early or retarding ignition. In this situation its possible for a component in your cylinder to overheat and create a glow plug. Then you are just a bad combination from pre-ignition and likewise a new cylinder and piston.
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