Tune

[TurboMike]

I've been thinking about tuning with the FAST setup.

For example:
Assume you have your VE numbers right on (meaning zero correction) throughout the rpm/load range and you decide to go 5% richer to see if the car likes more fuel. Couldn't you just add 5% to the VE number, and A/F ratio and the corrections numbers still be close to zero?

Could you just add 5% to the A/F ratio table and let the "tolerance" of the "closed loop limits" add the fuel (as long as it's within the percentages you have given in the limits)?

 

[55Belair]

I am fairly new to the system myself so take this for what is is worth.
From what I understand, once you have the VE table calibrated, leave it alone. unless you make other modifications to your engine that would change the aspects of your engine or the atmosphere changes so drastically (like driving into the mountains from sea level) that it would affect the engine. The ECU uses the VE table to determine how effeciently your engine is performing then makes adjustments accordingly.
If you want to change richen up your engine to see if it likes it, change the numbers in your AF target table. The ECU will reference your VE table and make the appropriate fuel changes to match this target.
If your VE table is calibrated correctly, there will still be no O2 correction. The O2 correction is a result of your actual O2 readings not matching your target AF table.

 

[TurboMike]

So you are saying that if you change your A/F numbers the system will automatically change the VE numbers (if your on target with the VE numbers to begin with)?

 

[summit]

Almost. It will change your fueling based on the VE numbers you have set. It is only using VE (volumetric efficiency) as part of a calculation to determine injector on time. Once VE are set correctly you should not have to change them unless you make a motor change like cam, heads, etc that would effect your motor efficiency. If you want to go leaner or richer you just change your target a/f ratio.
greg

 

[Lance]

If the system is properly calibrated, changing the a/f ratio will not require a change to the VE table. The VE table is used to calculate mass air flow and the a/f table is used to calculate fuel flow parameters from the mass air flow calculation.