Re: AFR adjustment via AFPR
Interesting topic for me right as I am working with my system to resolve rich AFR at low end and lean AFR at top end. I like others that are posting here and other threads are trying to get this topic nailed down. I also realize that this may be a dead horse for some of our members that have worked through these issues on their cars in the past. I would like to write what I think I know and hope to solidify my understanding and hopefully problems.
Fuel system factors;
1. Fuel pump - Fuel pressure and/or volume available for regulator
2. Fuel regulator – Controls what fuel pressure and/or volume is available for injector
3. Injector – Fuel volume capability, volume over a time frame
4. ECU – controls injector duty cycle (IDC) and timing based off of OEM input parameters (narrow band O2, boost) and modifies with short term fuel trims and ultimately long term fuel trims as well as real time timing advance/retard.
5. ECU tune – modifies what the ECU does with the injectors and timing due to limited ability of OEM inputs and no real time wide band inputs and automated adjustments.
I have read two ways to correct lean AFR here on our forum and both seem to have work based on feedback and tests people have shared.
Adjustable fuel regulator system by Needswings developed by Woody controlled by increasing boost through a Zt-2. This is described well on Robs website. I read that if the regulator is adjusted based on the boost that it should not run rich at lower rpm's and the stock fuel system has plenty of volume, pressure, and 450cc injectors would not run above optimal IDC.
or
The 550cc injectors (looped rail to even pressure) and high volume pump (SL55). I have also read that if you don't use the larger injectors and just install a higher lph pump then a tune can't have an effect on the AFR because the IDC is already maxed and would just be relying on increased pressure/volume behind the injectors since they would be opening for a longer period of time and more frequently at sustained higher RPM's (top end). Essentially a larger pump by itself would just make a larger reservoir of fuel available so that the injectors don't run out of volume or pressure especially with increased boost that the injector has to overcome. Adding larger injectors with a larger pump would give the ability of a tune (the ECU) to control the injectors and modify the IDC.
Once again, I am not an expert and this is only what I think I know based on what I have read and understand.
What I can’t figure out is why would the system run rich at low end in either scenario? Adjustable regulator with OEM injectors and pump shouldn’t cause anything to run rich at the lower end. Even if there was not an adjustable regulator and there was a larger pump the ECU should be able to keep it from running rich at low end. The larger volume injectors with larger pump shouldn’t either because the ECU could modify the IDC and timing as well.