RX8 4 Port MAF Calibration

[Dakath89]

Hey all,

I am looking for some guidance on how to calibrate my MAF on my S1 4port turbo

I have been trying multiple things to work it out but just cant seem to get my head around how to use the log to get the calibration required, I have megalog HD that I can use but just unsure where to go

Attached is 2 logs from today that are not super long but kept in closed loop as much as possible, any suggestions or formular to use MAF value, LTFT/STFT and rpm to work out what needs to be tweaked?

[mituc]

I'd say your current MAF calibration is not very much off, it's within reasonable limits. I'd leave it as is for now and eventually see what deviations you have once you go higher in the MAF voltage range once you will progress with your tuning.

[80HD]

Curious, is your maf in a tube similar to stock diameter? If not apparently you can do a formula working out the % difference in volume to apply to the maf voltages as a good starting point. But if you got it near spot on, perhaps this is moot.

[Walle]

its not really a good idea, as at low speeds, (of air) most of the flow is uniform across the tube.. the more the speed increases the more pronounced the gradient gets...

[mituc]

Curious, is your maf in a tube similar to stock diameter? If not apparently you can do a formula working out the % difference in volume to apply to the maf voltages as a good starting point. But if you got it near spot on, perhaps this is moot.

It is a good starting point BUT you need to adjust the calibration later. The coefficient is new_intake_diameter_squared/OEM_intake_diameter_squared. By example if you upgrade the factory intake, which is, say, 2.5" (I do not know if it's 2.5", I'm just giving an example) to a 3" ID intake, then the coefficient to multiply the original MAF calibration is 3*3/(2.5*2.5) = 9/6.25 = 1.44.
The reason why you need to adjust the MAF calibration even after applying this correction is that the lower the speed of the air (especially at idle and low load/RPM) the more the air will go around the MAF which will make it read lower. The intake design (if the MAF tube has an air straightener or not, if it has one then how is it made, and so on) as well as the cone air filter design may also have a measurable impact on the fuel trims and even AFRs if the fuel trims go above 20% or below -20%. -/+ 20% is the limit for the ECU still learning the fuel trims, between -/+ 20-25 it will only adapt the fueling as much as possible but will not learn the fuel trims, and then it will not read past -/+ 25. Depending on the car, if the deviation is too far off then the ECU may even shut the engine down.