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I have a question on compensation tables. I am a bit confused when it comes to IAT compensation. I see in both the dyno and road tuning courses you left this active while tuning the main fuel and ignition tables. I'm thinking this might be counter productive having them active while establishing the base map? Can you explain more on why you left it active?
In my reasoning I am thinking that all compensation tables should be disabled when tuning the base fuel and ignition maps, am I mistaken?
Also when you applied a correction factor on the IAT table of +/- 2.5%. Why did you choose standard temperature as the zero or reference point?
Hi Chris, great question.
The reason we should leave the IAT comp enabled when tuning is simply because the IAT will be fluctuating while we are completing our tuning session. Remember that the air density and hence AFR will fluctuate as air temp changes if we aren't compensating for it so if we turned the IAT comp off for tuning, we would be making changes in the main fuel table to account for any IAT fluctuation. This is more of an issue on a turbocharged engine but still a consideration on a naturally aspirated engine too.
If the IAT comp table is active and correctly configured, we can be certain that the AFR will stay constant as the IAT fluctuates and this means we can be effective in tuning the fuel table.
The point we choose for the '0' point in the table doesn't actually matter too much. The important part is that we vary by approx 2.5% every 10 deg C in temp. It's sensible however to use the standard conditions as the zero point for this compensation.
So on that note, are there any other compensations you recommend leaving on or is it only IAT and everything else should be set zero?
Just wondering the same as what Chris wrote - What other compensations should be left on when tuning?
You can leave all the compensations on -- the key is to tune the fuel when all the compensations are basically zero (ie, normal operating conditions). So be careful not to tune the fuel table until the coolant temp is 80-90 degC. If the IAT is too hot or cold try to bring it into the proper range, but if not make sure your compensation table is reasonable. The same with barometric pressure -- you can't usually control the weather, but any barometric compensation should be set to the standard (i.e. linear half the air means half the fuel).
BTW -- this is a 5 year old post -- good on you to go back and look through the history!
Thank you for the reply and information! All makes sense, thanks!