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Understanding AFR: Ignition Compensation

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Ignition Compensation

01.40

00:00 - While this course focuses on the fuel-delivery side of tuning, we've already seen that the air-fuel ratio can have an impact on the knock sensitivity of the engine.
00:09 Before we move on, I want to briefly discuss our options for compensating the ignition timing, too.
00:16 In general terms, the same compensations are available for the ignition map as the ones we've just discussed for the fuel delivery.
00:24 Understandably, particularly in an engine that is heavily knock-limited we want to use these compensation tables to help avoid the likelihood of detonation as heat and load increase.
00:36 In general, we'd use an air temp compensation table to remove ignition timing as air temperature rises.
00:42 And likewise, we'd possibly want to remove timing in sustained high engine loads and this can be done in the same way we've just addressed with the fuel compensations.
00:54 Be careful if you are using multiple compensations, though, as these can become additive.
01:00 What I mean by this is that if you're trimming perhaps three degrees of timing out due to air temperature, and another three degrees due to the sustained high engine load, you could end up with the engine responding poorly because of an overly-retarded ignition timing.
01:16 In turbocharged engines this can also result in boost control issues due to the higher exhaust gas temperatures.