High negative O2 correction at idle

Tuning a hilbourn injection system with 4 120 lbs injectors on a supercharged 350 ci. Running a fast xfi system. In the base setup I've had to lower the lbs to 50 in order for any start up or tune. The O2 correction is steady at -25. How would I correct that?

Hi dukeofsho,

I have had NO experience at all with any of the F.A.S.T systems.

Hopefully someone else on here maybe able to help you.

Regards

Dave.

I've tuned one FAST XFI system and it was a few years back so I'm struggling now to recall the tuning strategy. If my memory is right, the XFI uses a VE fuel model and for this to work properly it's essential for the ECU to know the engine capacity and the injector size/fuel pressure. For the same value in the VE table, reducing the injector size value would have the effect of the ECU supplying more fuel which is in line with your negative trims - The engine is way too rich. What happened when you had the injector size correct at 120 lb/hr?

Also your issue may be that the XFI is expecting 8 injectors and you are using 4 (I assume in a throttle body injection system). I can't recall if there is a parameter to set how many injectors are fitted to the engine.

I'm sorry I can't be more specific. Hopefully we have other XFI users on here. I'll also get this moved to the general forum.