Hi there,

I'm trying to understand how and when each of the tables interact when driving the car. From what I understand in stock form on a 1999-2000 ECU the MAF only kicks in around 4000 rpms, but the functions of the primary and secondary VE tables confuse me. Anyone care to explain to me how they interact with one another? I've searched for a few hours on and off and haven't found an explanation that I can completely understand. A link to a good thread would be appreciated too.

Thank you,
Ryan

 

You might want to move this to PCM Diagnostics and Tuning. You will get the attention of the right people there.

 

Good call, Maybe one of the mods will see this and move it to a more appropriate section.

 

Ryan,

So Main VE table values are used by the PCM during normal operation and the VE data is blended with the MAF data to create dynamic airflow up until the point it switches from dynamic air mass mode, which is usually around 4,000 rpm and goes straight to the MAF reading. The secondary VE tables are only used when the PCM sees a failed MAF sensor.

For tuning these tables. I disable the MAF by setting the high frequency for maf failure to ZERO then turn on the error code for high to DTC for first failure. I then tune the secondary VE table. With the secondary VE table tuned you can extrapolate the data to fill in the missing data on the primary VE table. Remember the engine runs on the secondary VE table when the MAF is disabled. Once I have the VE tables where I want them. I turn the MAF back on. I then tune the MAF table by setting the RPM to disable dynamic air to 400 rpm. Once those tables are close I enable the dynamic blend again. I usually shift to MAF only in the 3,000 rpm range. Finally the last bit of tuning I use the Main VE table to make slight tweaks to the areas with small errors when the blend is re-enabled. This process has worked for me on numerous black box vortec engines. Once you get everything dialed in the engine runs so much better.

Chris

 

Chris, this is a fantastic explanation. Thank you very much!