Quote:
Originally Posted by arghx7
There's a lot of discussion here among different people and scenarios that I'm trying to unravel.
First question: is this a matter of the fuel trims moving around more than would be ideal or is there an actual driveability, knock, etc problem?
Second: Are we talking about stock port injectors, obviously stock DI injectors, and stock MAF scaling or scaling that has been judged ok before the PI and DI balance was changed?
I suspect there's a bunch of wall wetting compensation, gas flow model, or injector flow compensation that is poorly understood because we don't have actual block diagrams of how the software works, just whatever has been reverse engineered.
My position is, generally speaking and subject to case by case revision--if the fuel trims are just moving around more who cares? That's their job. They're compensating for some inscrutable fuel calculation that hasn't been unraveled, or more likely, production tolerances in injectors, given that the stock values were for some mean spec part most likely.
 Is there an actual problem with the car here or are we just trying to make the fuel trim lines on an excel graph look pretty |
First: Getting DI and PI systems balanced made a driveability difference to my car - just went smoother.
Second: You would think that the Subaru engineers would be quite close with their stock MAF scales and fuelling algorithms. Some cars seem to be close to the mark, others not so. I was happy leaving the DI system stock on the hope that the engineers did their job, scale the MAF to that, then dial in PI system. I had planned to upsize my port injectors so it made sense for me to do it in that order to have a stable base to calibrate my port injectors to.
Third: I agree, there is a huge amount in the code that is not defined. I did disassemble the Tau transient fuelling tables, but have not been able to make sense of how to change them logically, so I've left them alone.
Finally: I'm happy to let the trims to their work and I have given up trying to control them around idle speeds, but I also like a pretty graph, even if the information it gives me is erroneous.