Thread: AFR questions

its my day off so all ive had to do today is search...

unfortunetly the only way ive found to do this is to keep the car in open loop... otherwise, while in closed loop, the NB 02 will try to keep it a constant 14.7 no matter what you have your command set to.

the only thing we can control command afr on the V6s in closed loop (again, this is what ive found in research so if im wrong someone please correct me) is through PE mode...

otherwise were screwed... but i have seen alot of threads that are telling e85 guys to change their command from 14.7 to like 9.8 or something? logically that doesn make much since to me but it could verywell just be a "V8" thing...

If you have a pretty good tune going and are ready to move on to something else, open loop tuning would be great to try. The fuel trims and stuff comes in handy in seasonal parts of the country, or when you are lazy and want to take a break in tuning, you can always go back to closed loop or narrowband.

Basically you disable the closed loop or narrowband/fuel trims from interfering with the fueling. Once you do that, you can plot commanded AFR vs. Actual AFR on the wideband and get a good tune going. Then you just tune it how you want it to run, if you want to run 15.0 in cruise you just replace the commanded 14.7 afr in the scan with 15.0 and get your new adjustments from that. There are open loop tuning tutorials on hptuner site, to get the info. for dhp it should be in clubgp in a few places. What i just said is just the basics of it.

For E85 tuning, they are talking about changing the gas AFR ratios in the pcm to ethanol ratios. This would take forever to do in our situation and may not yield the best results. Instead we are adding 33% fuel or so to the IFR table/injector table, not touching the afr tables, only realizing that while a gas AFR calibrated wideband reads 14.7, we are actually at about 9 ethanol stoich afr. Make sense? lol