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Temperature ignition&fueling compensation

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Is there a general method to predict how much timing must be reduced/fuel added to provide adequate engine safety?

Let's say you are tuning a car for the track and the conditionsin which the car is run vary from cold to extreme (situation right here at the moment). People don't understand that running a car for 30 minutes in 35celsius weather on the track is not really engine friendly - so if I wanted to make sure that the engine stays in one piece (at this point I don't really care about optimal power anymore) but there's no way to tell people to maybe cut a session short... The most that people maybe pay attention to is oil temp and that's about it...

Or is the right way just to properly set up knock control and hope it saves the motor in scenarios like this?

There isn't a single way of dealing with temperature compensations that you can apply to every situation. What you need to do will depend on the engine, how prone to knock it is, and how it is being used. What I try to do is replicate a worst case situation on the dyno and purposely cause high IAT to see how the engine responds. You can do this by blocking the intercooler and performing back to back dyno runs, or running with the hood/bonnet closed. This should allow you to test at higher IAT than what you would see under normal tuning conditions.

The fuel trim relative to IAT is generally used to maintain a consistent AFR as IAT fluctuates, however you can also choose to use this trim to move the AFR richer at extremely hot IAT to help reduce combustion temperature and safeguard the engine. Likewise testing at higher IAT can be used to trim the ignition to ensure the engine doesn't begin knocking.

Particularly with the IAT ignition trim on an engine that I find to be very knock prone, I will tend to retard the timing a little more aggressively beyond the range of IAT values I can actually test on the dyno just for safety sake.

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