Changing my AFR to run leaner
Changing my AFR to run leaner I have HPT and was wondering if anyone has changing the "AIF FUEL RATIO" under the engine/fuel control. Its set to 14.7 now, would changing that to 15.7 make a difference?
I know that this has some sort of blocker to make the US vehicles not go into Lean Cruze. Would that affect it at all?
TIA
I know that this has some sort of blocker to make the US vehicles not go into Lean Cruze. Would that affect it at all?
TIA
This is a fundamental constant and gets into everything so
I would leave it alone and correct.
If you want leaner cruise and closed loop operation then
you could play with the O2 switchpoints (vs Airflow Mode,
and maybe the Airflow Mode vs airflow as well, to get
yourself a decent range / resolution that covers your cruise
and light acceleration (sub-PE) driving. Then the more you
push down the O2 voltage thresholds the leaner you will
see the PCM "servo" the fueling, more negative trims. You
want to be sure you don't put the thresholds below where
you presently see the NBO2s bottoming, leave a little room
there, and realize that the NBO2 curve is sort of "S" shaped
and the closer you get to the limit voltages the more AFR
per volt change you see. Might log some wideband averages
initially and go at it in increments of (say) 50mV per tune
and record how much WBO2 AFR deflection you get from
that; be nice to know.
I would leave it alone and correct.
If you want leaner cruise and closed loop operation then
you could play with the O2 switchpoints (vs Airflow Mode,
and maybe the Airflow Mode vs airflow as well, to get
yourself a decent range / resolution that covers your cruise
and light acceleration (sub-PE) driving. Then the more you
push down the O2 voltage thresholds the leaner you will
see the PCM "servo" the fueling, more negative trims. You
want to be sure you don't put the thresholds below where
you presently see the NBO2s bottoming, leave a little room
there, and realize that the NBO2 curve is sort of "S" shaped
and the closer you get to the limit voltages the more AFR
per volt change you see. Might log some wideband averages
initially and go at it in increments of (say) 50mV per tune
and record how much WBO2 AFR deflection you get from
that; be nice to know.
Thanks for the replys guys.
Frost how does Lean Cruze get them into the high 15's or 16's without it running like crap?
Jimmy, I tried to play around with the switch points but I am not sure how well that is working. I added 150 to all the switch points across the board. By doing this it made the trims go negitive (think that means its very rich and then fuel will be automatically pulled to get it back to 14.7.
If I need/want it to be lean, that will infact make my fuel trims +, which will mess up my WOT (theory that its not good to have positive trims going into WOT). So what would the trick be here?
Frost how does Lean Cruze get them into the high 15's or 16's without it running like crap?
Jimmy, I tried to play around with the switch points but I am not sure how well that is working. I added 150 to all the switch points across the board. By doing this it made the trims go negitive (think that means its very rich and then fuel will be automatically pulled to get it back to 14.7.
If I need/want it to be lean, that will infact make my fuel trims +, which will mess up my WOT (theory that its not good to have positive trims going into WOT). So what would the trick be here?
lean cruise is enabled during very low (numerically high) MAP areas that are near steady-state at a predetermined MPH window. As out US vehicles (or at elast calibrations) don't really allow tinkering, there are certainly some other hidden parameters. Nearly any positive throttle delta should break the routine and standard enrichment will follow. It is a fine line to walk and no offense, but you need to really understand all of what is going on here before focusing on something like this. Though you will alter what is perceived to be stoich through switchpoints, it will also lean you out in other less desireable steady-state areas. Personally I think if you REALLY want to do this, OL is the best bet. Good luck.
Originally Posted by Frost
lean cruise is enabled during very low (numerically high) MAP areas that are near steady-state at a predetermined MPH window. As out US vehicles (or at elast calibrations) don't really allow tinkering, there are certainly some other hidden parameters. Nearly any positive throttle delta should break the routine and standard enrichment will follow. It is a fine line to walk and no offense, but you need to really understand all of what is going on here before focusing on something like this. Though you will alter what is perceived to be stoich through switchpoints, it will also lean you out in other less desireable steady-state areas. Personally I think if you REALLY want to do this, OL is the best bet. Good luck.
I have a good base tune, it shifts good, so I figured I would mess around with the switch points and afr in the cruse area to see what I can do for the mpg. I am not looking to get 30 mpg, and all my tunes are done when I am going somewhere, so I am not wasting a bunch of gas for nothing. I just would like to see what points can be altered to better the tune for not just me, but anyone that is looking to pick up a few mpg.
The way I am looking at this is that, if I can lean it out to say 15.7 in cruise safely without affecting anything else, then why not?
Thanks for the feedback guys and any further info or tips is welcome!
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I am not sure about HPtuners custom operating systems but the EFIlive cos3 & above has a map rpm based fuelling table that allows you to command fuelling by your load points. With this you can set up a pseudo lean cruise by leaning out your lower map areas.
Holden in there standard system will command an AFR in the high 16's without a lean stumble. The trick is to optimize the timing in these areas. Usually you will need to bump it up a bit.
Holden in there standard system will command an AFR in the high 16's without a lean stumble. The trick is to optimize the timing in these areas. Usually you will need to bump it up a bit.
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Verdad Gallardo Running OLSD I was able to get some stable cruise in just a few cells into the low 16s(transitions were touchy too), but after all of the work I got a savings of 6-8% in about 3 cells and even after some extended highway travel the overall savings were very hard to see in the real world. FWIW the tune on my TA is still like this down low. Forgive my lack of enthusiasm 
I'd just rather have that afternoon back. Good luck though, if nothing else, tinkering like this always proves educational.
I'd just rather have that afternoon back. Good luck though, if nothing else, tinkering like this always proves educational. 
Staging Lane
Joined: Jan 2004
Posts: 84
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From: Calgary, Alberta, Canada
Take a 20 minute log of your highway driving at your normal speeds with cruise control on. Map g/sec airflow against VE. Tweak your O2 switch points and mode tables to tell the PCM that a leaner millivolt setting is stoich. Result, better fuel mileage and minimal impact on performance.
Originally Posted by Billf6531
Take a 20 minute log of your highway driving at your normal speeds with cruise control on. Map g/sec airflow against VE. Tweak your O2 switch points and mode tables to tell the PCM that a leaner millivolt setting is stoich. Result, better fuel mileage and minimal impact on performance.
