First attempt at CALC VET please check for sanity

[Strong05]

This is probably a dumb question but what is DAT? I don't recall that being discussed in any of the CALC VET threads I've caught up on.

Thanks,
Brad

[joecar]

Brad,

DAT is this thing: ({GM.DYNAIRTMP_DMA.C}+273.15)

I separated that out as CALC.DAT so you can display CALC.DAT.F on the chart/gauge (so you can check that DAT falls between IAT and ECT).

[Strong05]

dang it... I just checked B0120 and it's set to 4000... could have swore I set it to 400.

[Strong05]

Interesting that they use Kelvin... Whats the significance of that being between IAT and ECT? Where/how is the ECU coming up with DYNAIRTMP?

[joecar]

Interesting that they use Kelvin... Whats the significance of that being between IAT and ECT? Where/how is the ECU coming up with DYNAIRTMP?

The PCM blends IAT (intake air temp) and ECT (engine coolant temp) to calculate the temp of the air entering the cylinders... the internal pid for this is DYNAIRTMP_DMA;

DAT takes that and makes it easily accessible in Kelvin, since the calculation uses the Ideal Gas Law PV=nRT (from Physics) to calculate the VE table.

[Strong05]

Guess that means this is basically garbage... oh well at least it's supposed to be a super nice out for a drive this weekend! Thanks for taking a look at it for me Joe!

[Strong05]

Gotcha, despite my best efforts to flush thermo from my memory I still recognize that equation. Just don't ask me to use a look up chart or to interpolate anything!

[joecar]

dang it... I just checked B0120 and it's set to 4000... could have swore I set it to 400.

Guess that means this is basically garbage... oh well at least it's supposed to be a super nice out for a drive this weekend! Thanks for taking a look at it for me Joe!

Yea, I know, stuff happens...


You might be ok, because the transient filter will remove any data contributed by transients which includes when the VE kicks in...

just try it to see, but yes, back it up with another log, see if you get the same result.

[Strong05]

Interesting I thought the transient filter was just for the throttle. I'll probably do another run tomorrow just to be safe. I might take a look at both and see if there are any differences. I think the tune is pretty close as it is. I only changed the cat back part of the exhaust and the throttle body from when I tuned it last.

[joecar]

When the throttle moves (causing a transient airflow/airmass condition), if the RPM is under B0120 then the VE kicks in (the PCM has some algorithm for this)... so the transient filter just happens to remove VE contributions... but yes, it is better to take another log with VE disabled (via B0120).


Here is what I get from your log file when I hide low count cells and apply the transient filter (paste CALC.VET into VE and paste-multiply CALC.SELBEN into MAF), see attached.