Lack of fuel @ WOT - E38

[HTMtrSprt]

What is the reason that an E38 ECM in a boosted application will not recognize higher than stock air mass at low RPM (below the "high speed mode" entry point) even though it has a 2 bar MAP and properly reconfigured virtual VE tables. It is happening in multiple cars. Go wot below the high speed mode parameter - calculated engine airflow shows as high or higher than mass air sensor engine airflow and MAP reads 180 kpa but the grams air/cylinder reads low, there is low inj pw and the timing is as listed for the low grams air/cylinder. When the rpm crosses into high speed mode, the inj pw suddenly doubles, and the timing drops to where it should be for a boosted application. So far my only solution has been to set high speed mode to just above idle speed.

[swingtan]

Post a log and a tune....

Did you tune the 1bar VVE as well as the 2 bar VVE?

Also check...

{B8034} : This will lock the MAP value to the defined figure ( stock NA is 105kPa ) for calculations. While the MAP PID will read higher, the ECM will use this value as the MAX.

FWIW, there is probably no issue with running MAF only.

[HTMtrSprt]

B8034 is set to 200 kpa. All the VVE tables have had their coefficients altered to the same parameters - as I said, the scans show the ECM is seeing the correct MAP pressure and air mass entering the engine.

[swingtan]

Post a log and a tune....

[gmh308]

What is the reason that an E38 ECM in a boosted application will not recognize higher than stock air mass at low RPM (below the "high speed mode" entry point) even though it has a 2 bar MAP and properly reconfigured virtual VE tables. It is happening in multiple cars. Go wot below the high speed mode parameter - calculated engine airflow shows as high or higher than mass air sensor engine airflow and MAP reads 180 kpa but the grams air/cylinder reads low, there is low inj pw and the timing is as listed for the low grams air/cylinder. When the rpm crosses into high speed mode, the inj pw suddenly doubles, and the timing drops to where it should be for a boosted application. So far my only solution has been to set high speed mode to just above idle speed.

It is not uncommon in boosted apps to set the MAF high speed mode to say 1000rpm.

So you are running a MAF and tuning the VVE? Are you using a calc PID to calc air mass flow, or looking at the SD MAF (VVE) PID?

[HTMtrSprt]

Here is the tune file and data log.... note that the log was with a tune that had a 3000 RPM switch point for high speed mode. Check the beginning of the run... note the inj pw and air/cyl just before and after 3000 RPM.

[HTMtrSprt]

What about turning B8037 and B8038 up to 100? Is there an airflow model in the background and when the actual MAP exceeds the error limits in these params, it defaults to this background airflow table?

[gmh308]

Here is the tune file and data log.... note that the log was with a tune that had a 3000 RPM switch point for high speed mode. Check the beginning of the run... note the inj pw and air/cyl just before and after 3000 RPM.

Was your VVE setup with MAF disabled?

EDIT: just took another look at your VVE. How did you manage to get your VVE airflow reduced by so much at low map values? Like halved in some cases.

[HTMtrSprt]

Was your VVE setup with MAF disabled?
?????????

[gmh308]

?????????

Well I assume the question marks mean "what do you mean..?"

MAF needs to be disabled and the engine running in open loop (O2's/trims disabled0 to set the VVE airflow model up.

If you havent seen Swingtan's definitive VVE setup guide, take a peek..... :).

[HTMtrSprt]

Was your VVE setup with MAF disabled?

EDIT: just took another look at your VVE. How did you manage to get your VVE airflow reduced by so much at low map values? Like halved in some cases.

The VVE table HAS been set up properly..... this car has a cam in it w/ long tubes - the engine moves less air at low speed and low MAP pressure. It starts and drives flawlessly with computed (speed density) air flow numbers matching the MAF air flow numbers at idle and part throttle cruise with no problems on transitional throttle. The data log shows this as computed total airflow is the same as MAF total airflow, but the ECM seems to be disregarding the computed air flow number and using some sort of backup number as evidenced by the air/cylinder parameter showing half air/cylinder that it should until high speed mode.

[gmh308]

The VVE table HAS been set up properly..... this car has a cam in it w/ long tubes - the engine moves less air at low speed and low MAP pressure. It starts and drives flawlessly with computed (speed density) air flow numbers matching the MAF air flow numbers at idle and part throttle cruise with no problems on transitional throttle. The data log shows this as computed total airflow is the same as MAF total airflow, but the ECM seems to be disregarding the computed air flow number and using some sort of backup number as evidenced by the air/cylinder parameter showing half air/cylinder that it should until high speed mode.

Ok that completes the picture. There are other background factors that GM uses to correct the VVE model. Moving the VVE a considerable amount like you have had to (cam/blower/longtubes etc) can mess the correlation up. Which is why with a lot of S/C apps it is simpler in aftermarket apps just to run 100% MAF from low rpm which bypasses the low speed headaches.

Even aftermarket S/C kit manufacturers that are close to the factory do this. :)

[gmh308]

Ok that completes the picture. There are other background factors that GM uses to correct the VVE model. Moving the VVE a considerable amount like you have had to (cam/blower/longtubes etc) can mess the correlation up. Which is why with a lot of S/C apps it is simpler in aftermarket apps just to run 100% MAF from low rpm which bypasses the low speed headaches.

Even aftermarket S/C kit manufacturers that are close to the factory do this. :)

Looks like Ross had added in these VE correction tables in the latest definitions in the Airflow section. "VE Compensation".

Swingtan: these may interest you for MAFLess VVE fine tuning.

[swingtan]

The only problem, is that I'm running the old private Beta COS with the Valet mode.... so no updated calibrations for me :( I'll have a look though.