Fuel models

Is it possible to vary the duty cycle of stock injectors when reflashing a factory ecu?

at 5.46, by "defining what the VE is" do you mean you are telling the ECU what you WANT the VE to be at each individual cell or are you making modifications to the VE that the different load sensors are plotting on their own? Basically, is it the tuner that tells the ECU what VE to run or is it the ECU that tells the tuner what VE the engine is running at each individual cell? (pardon me if both of them pretty much sound like the exact same thing).

Yes we can certainly adjust the duty cycle of the stock injectors and essentially this is how we make changes to the AFR.

The VE of the engine is an element of it's mechanical design and as such we don't influence it unless we actually make changes to the engine. From our perspective as far as tuning is involved, we're adjusting the VE table until the measured AFR matches the target. Assuming the injector data is also accurate, this then means that our VE number match the real VE of the engine.

Ok I understand. So VE follows the target AFR we are trying to achieve. So what are the mechanical changes when you adjust the VE table?

A camshaft change for instance would be a "mechanical change" and you would need to change the VE table.

There are no mechanical changes taking place when you adjust the VE table. We're simply adjusting the VE table value until it matches the actual VE of the engine. We know when we have this correct because the measured AFR will match our target AFR value. Once the engine is tuned then you would need to change the VE table only if you make a mechanical change to the engine that will affect the VE (such as the cam change Chris has mentioned).