I'm having an issue with my MS3. I tuned all my settings during the Spring/Summer months and had a good tune. The car ran great, idled fine, AFR's were where they should be. Now that it's Fall here, the outside temps have dropped quite a bit. My tune is way to rich all over. Is there a setting in tunerstudio or on the MS3 that can correct the AFR's without having to retune now and then switch maps once Spring comes around again?

 

what firmware? you need to adjust your MAT correction curve to keep the AFRs where you are used to seeing them.

 

I'd have to look to see what firmware, but I just updated itaround August to the new firmware. Ok, I'll look into the MAT settings, just trying not to have 2 maps.

 

newest has the tab under basic called "air density correction" or something.

mine basically looks like a bow or smiley face: richens up slightly under 60*, stays flat 70-100, then richens up again slightly past that (so the car doesn't pull fuel if it heat soaks)

so far so good, and we have HUGE temp swings here in CA between daytime and nighttime

 

mine looks like this right now:

 

I wasn't on the latest firmware. Once I upgraded the unit the settings were there under "Basic Settings" I was able to adjust them to a "better" config.

 

What imperfection does this curve adjust for, over a well-calibrated AIT sensor?

 

Air density. The AIT sensor feeds the table.

 

As I Understand MS, Air Density is handled, first order, by the AIRDEN variable in the equation for REQ_FUEL. So I was thinking this additional curve might be for correcting for deviation of air from the ideal gas law, but perhaps for some other nuance.

EDIT: But now I see that AIRDEN is a constant, taken at one condition os temp and pressure, so, yeah, it is the correction for absolute temp. However, it is adjustable for some reason.

 

that curve IS the ideal gas law code. It used to be built into the algorithm, but the law on paper didn't really transfer well into real life scenarios on the car. Then you'd basically tune a correction curve to combat the code. So they changed the code. The default curve when loading a fresh map is the ideal gas law; the code I posted altered it significantly.

 

I put those in today. Amazing how flat this is, demonstrating how little effect air temp actually has on density, or conversely, how much divergence air has from an ideal gas.

Car held AFR's much better as the AIT changed.

 

Yeah so just tune it from there. If you get your fueling in-check and start noticing it leaning out or going rich at extreme temp ranges, you can correct with the curve.