Resumen

00:00 - Key has asked, can I explain a little bit about air temperature and coolant temperature compensation to fuel and ignition timing? Yeah there's a fair bit to this and again a lot of it comes down to what you're trying to achieve.
00:13 Let's deal with our air temperature compensation for a start and what we need to understand here is that as the temperature of our inlet charge air changes, so does the density or in other words the mass of air that is contained in a given volume.
00:27 And remembering that our air/fuel ratio is a mass ratio.
00:31 This is really important because we need to adjust our fuel delivery as the air temperature changes.
00:38 So generally there will be a background compensation map inside of the ECU that does this, so we don't really need to think about it too much.
00:45 As a general rule of thumb, we need to change the fuel delivery by about 2.5-3% for every 10°C change in air temperature.
00:53 As our air heats up it becomes less dense, so in order to maintain a consistent air/fuel ratio, we need to reduce the fuel delivery.
01:02 Conversely as the air cools down, it becomes more dense so we need to add more fuel.
01:06 Now there are other aspects there, that will maintain a consistent air/fuel ratio but that may not be what we want to actually.
01:13 Perhaps as the air temperature becomes very hot, we may want to actually target a richer air/fuel ratio in order to help protect the engine because at hotter temperatures, it may be more prone to detonation.
01:24 So again really comes down to the tuner's specifics of what they're trying to achieve.
01:29 Likewise with our ignition timing, generally while there will be a small change in optimal ignition timing with our air temperature change, generally this is more used as a safety precaution so for example with a turbocharged engine, if the air temperature heats up, we may find that our engine becomes very sensitive to knock or detonation so we may choose to purposefully retard the ignition timing a little bit at hotter inlet charge temperatures.
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