Hey all,
I understand that the numbers in open loop fueling are arbitrary and do only go off what the wideband is showing, however, I'm having to command 8.6AFR in the high octane fueling tables to get my desired 11.5 on the wideband. This seems super excessive to me. After searching around I've seen that most people only have a 1.0-.5 afr difference between the commanded afr and actual afr. Not sure what is going on here. Fuel trims are all good and my maf has been properly scaled for my intake (at least, i think so. maxing out in some areas to 255. Any way for more resolution?) . Should I really not be concerned about this much of a difference? Seems like something has to be way off for the open loop to be that far away from actual AFR. Again, closed loop fueling is all accurate, Trims +- 5% at idle and cruise. Stock injectors. Any help appreciated. Thanks

2006 Evo IX SE
Mods:
ETS intake
ETS intercooler
ETS LICP
ETS Catback Exhaust
ETS Catless downpipe

 

my guess would be you need a fuel pump upgrade.

 

I was thinking it could be fuel pump related but if it was, wouldn’t I be leaning out regardless of how much I command in the fuel tables?

 

Your over thinking it. Your system isn't maxed out, but your pump is falling short. You are compensating for that by adding more fuel (IPW). It's pretty well known that even lightly modded evos can exceed the capabilities of the stock pump.

Edit: if my answer is a little too hand wavey for you, go take a look at the flow chart for a walbro 255. Specifically notice the flow at different pressures. Hopefully that will help.

 

to answer your other question, yes you can rescale your maf table to read higher, but you can't make the table bigger so you have to shift it and free up some cells for those higher frequencies. I rescaled mine as mrfred did here

https://www.evolutionm.net/forums/ec...ing-notes.html

 

Gotcha. That makes a lot of sense. Wasn’t thinking about higher commanded AFR = to more IPW to compensate for the lack of pump. Thank you for your help!! Pump upgrade ordered and on the way.