PE question.
05-13-2009, 10:24 AM
#21
TECH Senior Member
Now I am seeing how it all works together. I knew how to go about tuning the car as far as how to setup the scanner and what tables to adjust according to the wideband. Just wanted to know how the computer interprets all this and then determines the amount of fuel. So if no airflow characteristics of the engine change then VE can be left alone.
If you change the commanded OL table or the PE table, then the VE table can be left alone...
step 3 computes the fuelmass needed for the airmass (step 1) to meet the looked up AFR (step 2).
If you change the airflow characteristics, you change the cylinder airmass...
i.e. VE table will have to now be changed as JonCR96Z said.
05-13-2009, 01:52 PM
#25
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Closed-loop.
Being someone sarcastic, but in reality utilizing a stock setup 'most' of idle is VE Table related, and normal driving is primarily MAF with airflow correction(s) from the VE Table.
A good tune will have your airflow from the VE Table and MAF relatively identical. Getting there is not easy, and so far I have not found one shortcut...short of utilizing Trim functions through closed-loop.
Even that has it's inherent flaws, but you can get your tune close and let Trims clean it up.
I am not sure I would say MAF is 'linear'. There are a lot of frequency's and airflow, and it becomes exponential as you go up the scale.
After a year of doing this, I learned to go back to basics. Trying to create your own hybrid tune never seems to work.
I would just stick to one system and get your airflow and AFR dialed in. Then it will all work.
Good luck..
..WeathermanShawn..
Being someone sarcastic, but in reality utilizing a stock setup 'most' of idle is VE Table related, and normal driving is primarily MAF with airflow correction(s) from the VE Table.
A good tune will have your airflow from the VE Table and MAF relatively identical. Getting there is not easy, and so far I have not found one shortcut...short of utilizing Trim functions through closed-loop.
Even that has it's inherent flaws, but you can get your tune close and let Trims clean it up.
I am not sure I would say MAF is 'linear'. There are a lot of frequency's and airflow, and it becomes exponential as you go up the scale.
After a year of doing this, I learned to go back to basics. Trying to create your own hybrid tune never seems to work.
I would just stick to one system and get your airflow and AFR dialed in. Then it will all work.
Good luck..
..WeathermanShawn..
