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Ideal gas law, MAT correction

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So under my thinking and what ive notice in using auto tuning features on my platform, ive noticed from day to day and in different temps its either adding or taking fuel from the VE. so my question is how do you set the MAT correction its a 2d graph using mat temp and fuel % if i get everything dynod in steady state one day and have to come back for the low loads that i couldn't get to the bin on a different day/temp wouldn't it be off at those lower load areas, is this when you go back and forth using ego correction numbers to dial the ve in so the mat correction stays at the same setting as when it was dynod so it's good for everything else? what is the proper way to tune this?

If you use a VE model based ECU - it should apply an air temperature correction automatically, even if the air temperature correction table disabled. The table allows you to make an additional adjustment.

What I'm asking if you tune everything above 50kpa at say 100f and the next day you road tune the lower kpa at 80f how do you set the cruve on the mat table so that it will keep you afr's throughout in whole. VE table? Is this where you set the Mat table first for everything then Just use ego correction to determine where to set the VE table?

If you are tuning an ECU that uses a VE fuel model then normally the MAT is accounted for automatically and often this type of ECU won't offer an IAT correction table that's user tuneable. Some still do offer this (Haltech for example) but it's used to 'fudge' the auto correction if required.

If your ECU is injection time based then the IAT correction will likely be user tuneable. The relationship between air density and air temperature isn't perfectly linear however across the range of temp we are likely to see in the engine you can average the percentage change in air density to approximately 3% per 10 deg C change in air temp. Apply this same adjustment to your fuel trim table and you will be very close. I normally set 20 deg C as the zero point and add fuel below and subtract above.

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