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Discussion and questions related to the course EFI Tuning Fundamentals
Okay, so I haven't completed the Understanding AFR, but I'm 67% through with it. and completed the EFI Fundamentals and Road Tuning courses.
As I was going through Understanding AFR, i kept getting hit with the AFR Target table. I've seen that before, but How does that correspond with the VE Table?
Is the AFR Target Table a correction factor table that makes finer adjustments to the VE Pulsewidth calculation or is it a closed loop type of tuning function that works independent of your VE table? I'm missing the connection somewhere.
OOPS I reported the post hoping it gave me an option to tell you I think I posted it in the wrong section... It didn't! Sorry! I think this should be under Understanding AFR.
The AFR Table (Fuel Aim) tells the ECU what Lambda value you want the engine to be operating at at that load point, where the VE Table tells the ECU how efficiently the engine is breathing, thus from that the ECU generates a Air Mass value. Once it has the Air mass value, it looks up the Fuel Aim table for the Lambda value, and calculates the amount of fuel mass versus air mass needed to get to the aimed for Lambda. This then generates the actual pulse width value the the injectors need to be opened for.
I was going back through all the videos and I knew I missed something critical, I had been researching the MegaSquirt products and they do VE, but many people tune a VE table and don't reference an AFR Table at all, so their VE tables are like from 40% up to 180% and it always confused me.
From my experience I've always tuned Alpha-N for load (Before I knew it was even called that) and Pulsewidth w/ AMP (Absolute Manifold Pressure) Correction with PerfectPower products, so the whole AFR Target was super foreign under the VE way to tune.
I think I'm going to like tuning VE with AFR target a great deal more.
Thanks a lot for the clarification.
Many people who don't understand the VE based fuel model concept can get into trouble with their tuning as it's quite important to follow the correct work flow during the tuning process otherwise you'll end up wasting time as you'll need to go back and re-do some of your work. The example I'm thinking of here is that many tuners ignore the AFR target table and concentrate their tuning on the efficiency table. While you 'could' get the engine tuned like this, the resulting VE table won't represent the actual engine efficiency and you won't be able to make changes to your target AFR in the AFR target table like you could with a properly tuned VE model.