gm.trqeng

[dian]

99 c5. what are the inputs for torque in a stock tune? what happens if you loose the maf? and how is it with cos3 and (e.g.) a 2bar map?

(gm.trqeng seems to yield same values as gm.trqtrans. any thoughts on that?)

edit: this is what im seeing at 200kpa/no maf. (i cant upload scan for some reason.) rising ibpw to redline, dyncylair rising to redline (1.90 max), torque peaking at 3800* with a (quite realistic for max) value around 800 nm, acceleration fluctuating but highest at 5000-6000, calc.power rising to redline with 500 rwhp max (not unrealistic, a bit low). in a stock cofiguration i see max torque at 450 nm (engine rating is 475).

*140kpa

[nonnieselman]

Ive never tuned a MAF for boost so i have no idea on this one.

[dian]

speaking of dyncylair: its seems overreported by about 40% in the cos3 tune.

stock car reports 0.71 g at torque peak. 0.721 liters x 1.175 (15 degrees c, 300m, 50%) is 0.846 g, working out to 84% vol. efficiency. cos3 reports 1.71 g at 5500rpm/190kpa*. 0.721 liters x 1.117 (30 degrees c, 300m, 50%) is 0.795 g x 1.9 p.r. = 1.51 g. 1.21 g at 80% efficiency. 1.71/1.21=1.41. it would mean 113% cylinder filling.

any thoughts on that? if the inputs were known the numbers could be somehow scaled back, i guess.

*i took this point because the 2bar map is still well within its range.

[joecar]

GM.TRQENG and GM.TRQTRANS should read the same for combined engine/trans PCM.

[joecar]

When MAF fails PCM sets a MAF DTC, sees this and then does SD (VE table) only.

[joecar]

So you need to get both MAF and VE tables corrected.

[joecar]

In COS3 are you MAF-less (i.e. SD, VE only)...? How did you verify this (or not this)...?

If SD might have to look at temperature correction airmass tables.

[dian]

maf is gone.

so are you saying the ecu looks at map and iat only to calculate torque/dyncylair? (obviously it understands boost wit cos3.) how does it then happen it thinks they are highest at low rpm/bosst (3800/140kpa)? iat* is the same and i surely do not have the largest v/e numbers in the midrange, they are rising up to redline.. a stock car reports highers tq/cylair around 5000 btw.

*in both cases maf would be well beyond the 120g/s blending table limit

[joecar]

ECU first calculates airmass using MAF and/or VE, it then calculates everything else, including fuel mass and ignition advance.

[joecar]

Are you getting a MAF DTC...?

[dian]

dtc has been programmed out for 7 years now.

so no thoughts on what im seeing?

[joecar]

ECM ignores MAF only if MAF DTC shows up.

[joecar]

Without MAF DTC, ECM is using both MAF and VE at different times/conditions.

[joecar]

You can program MAF DTC's to not light up the MIL when the DTC is present, but this is not the same as disabling the MAF DTC's

[dian]

there is no maf and no maf signal. the ecu cant be using it, right? or am i misunderstanding what you are saying?

[joecar]

You did not misunderstand me :)

Log SAE.MAF and see what it shows.

[dian]

2.52 steady.

[dian]

so you are saying the maf might not be properly "failed" in the tune and is somehow contributing to the torque calculation in an inappropriate way (while cylinder mass is calculated correctly)?

what im seeing is this: torque in blue compared to dyncylair and ibpw in the maf-less cos3 tune.

edit: the roads were finally dry (after several weeks), so i "failed the maf" on a stock setup/tune and did some logging. there is no big difference, torque follows ibpw/dyncylair like it should. max is around 5200, probably because the (stock) ve table is rising up to redline. its also a bit lower as about 10 degrees get pulled, but thats it.

so again: what could make the torque read highest at 3800 with cos3 and centri boost?

(btw, i cant attach any files larger than 1 mb in here? if i wanted to post a logg, how is that done? i cant even post a print screen.)

[dian]

i finally fixed it.

trqeng was not showing realistic numbers as indicated by e.g. dyncylair. my b0120* was still set to 4000. i changed it to 8000. now trqeng works like it should.

its simple and makes sence. however i dont remember to ever seeing this mentioned anywhere and all cos tunes i now looked at have 4000 in it with a failed maf. so its somewhat weird.

anyways, now the trans, traction control and torque limiting should be much easier to handle.


* RPM Threshold For Airflow Calculation

[dian]

oh, no, please disregard the above. on the next outing it logged as before, even worse, the torque peak being at 3200 (was 3600-3800 before).

so the system for once remembered what its supposed to do and then immedietely forgot it again?