Can bolt-on mods offset rich A/F ratio?
04-05-2005, 07:44 PM
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Staging Lane
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Can bolt-on mods offset rich A/F ratio? From some reading done here on LS1tech.com:
Seems that most of the trouble with some of the major bolt-ons (like headers) is that when just driving around normally the PCM learns to add more fuel to maintain the A/F ratio and thus the LTFT is a positive number. (There is also that problem with the O2 sensors being farther away and colder -- but I am not sure whether this causes a rich bias too.) This causes an overly rich condition when the engine goes WOT because of the cruising rich bias is added to the PE value and often results in too much fuel for the air flow improvement. If this is correct...
1) is there a way to fool the PCM into leaning out the A/F at cruise? Something like the timing tricker but instead of tricking it to think the inlet air temperature is colder, make it think it is hotter?
2) do some bolt-on mods (ported MAF ends?) cause the PCM to go leaner? If so can they be used to offset the rich condition that something like headers can cause?
Thanks!
Seems that most of the trouble with some of the major bolt-ons (like headers) is that when just driving around normally the PCM learns to add more fuel to maintain the A/F ratio and thus the LTFT is a positive number. (There is also that problem with the O2 sensors being farther away and colder -- but I am not sure whether this causes a rich bias too.) This causes an overly rich condition when the engine goes WOT because of the cruising rich bias is added to the PE value and often results in too much fuel for the air flow improvement. If this is correct...
1) is there a way to fool the PCM into leaning out the A/F at cruise? Something like the timing tricker but instead of tricking it to think the inlet air temperature is colder, make it think it is hotter?
2) do some bolt-on mods (ported MAF ends?) cause the PCM to go leaner? If so can they be used to offset the rich condition that something like headers can cause?
Thanks!
04-06-2005, 01:02 AM
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Originally Posted by More power!
From some reading done here on LS1tech.com:
Seems that most of the trouble with some of the major bolt-ons (like headers) is that when just driving around normally the PCM learns to add more fuel to maintain the A/F ratio and thus the LTFT is a positive number. (There is also that problem with the O2 sensors being farther away and colder -- but I am not sure whether this causes a rich bias too.) This causes an overly rich condition when the engine goes WOT because of the cruising rich bias is added to the PE value and often results in too much fuel for the air flow improvement. If this is correct...
1) is there a way to fool the PCM into leaning out the A/F at cruise? Something like the timing tricker but instead of tricking it to think the inlet air temperature is colder, make it think it is hotter?
2) do some bolt-on mods (ported MAF ends?) cause the PCM to go leaner? If so can they be used to offset the rich condition that something like headers can cause?
Thanks!
Seems that most of the trouble with some of the major bolt-ons (like headers) is that when just driving around normally the PCM learns to add more fuel to maintain the A/F ratio and thus the LTFT is a positive number. (There is also that problem with the O2 sensors being farther away and colder -- but I am not sure whether this causes a rich bias too.) This causes an overly rich condition when the engine goes WOT because of the cruising rich bias is added to the PE value and often results in too much fuel for the air flow improvement. If this is correct...
1) is there a way to fool the PCM into leaning out the A/F at cruise? Something like the timing tricker but instead of tricking it to think the inlet air temperature is colder, make it think it is hotter?
2) do some bolt-on mods (ported MAF ends?) cause the PCM to go leaner? If so can they be used to offset the rich condition that something like headers can cause?
Thanks!
your Q's
1) There is no sense in doing any "trickery" to make you car run right. Tune it RIGHT and it will run RIGHT. Trickery = crappy fueling despite perhaps achieving desired AFR production. Let's use the EFI system the way it was meant to be.
2) MAF mods significantly affect fueling since this is the main determinant of airflow. Any changes to the MAF would require a new calibration to accurately reflect the airflow that is measure across the housing volume.
