quick tuning questiona..E85 and open loop and O2 sensors
03-24-2012, 05:10 PM
#1
quick tuning questiona..E85 and open loop and O2 sensors Just a quick question on e85 and open loop tuning. I'm building a track only turbo car, and it will pretty much just be tuned for WOT and idle, not really any driveablility. I plan to still use the stock ecu for the time being. Car is currently set up on a 3bar OS via HP Tuners. Is it required to run O2 sensors when tuning only for open loop? I know to change the stoich afr to compensate for E85, but im just curious as to how the pcm knows how to compensate for the fueling if it has no O2 readings? Will i have to rely on my VE table being correct via wideband tuning? Just trying to get some clarification. If its necessary to run o2 sensors I will, but if I can get away with it, i'll just ditch them.
03-24-2012, 10:07 PM
#2
Fuel trims and VE table have two different function, even though they both contribute to the final result: the pulse width, or as most people 'see' it, AFR on the wideband.
VE is one of the main components in airmass estimation.
Fuel trim are a corrective mechanism on the fueling side.
The process goes:
1. estimate airmass (using VE and other variables in case of the pure SD operation)
2. convert airmass to fuelmass (that's just division by AFRcommanded)
3. calculate injector pulse width (using manifold pressure, injector flow, all kinds of other variables)
4. apply a correction to the pulsewidth based on fuel trims (this occurs in CL only)
The stock ECU doesn't know how to use a WB to do trimming. Stock operation is OL at WOT. So if WOT is all you care about, CL and NB O2's are only really useful for idling and going to/from pits. Without trimming, your final fueling decision will be made purely out of VE and other variables from the SD model, and the injector data.
VE is one of the main components in airmass estimation.
Fuel trim are a corrective mechanism on the fueling side.
The process goes:
1. estimate airmass (using VE and other variables in case of the pure SD operation)
2. convert airmass to fuelmass (that's just division by AFRcommanded)
3. calculate injector pulse width (using manifold pressure, injector flow, all kinds of other variables)
4. apply a correction to the pulsewidth based on fuel trims (this occurs in CL only)
The stock ECU doesn't know how to use a WB to do trimming. Stock operation is OL at WOT. So if WOT is all you care about, CL and NB O2's are only really useful for idling and going to/from pits. Without trimming, your final fueling decision will be made purely out of VE and other variables from the SD model, and the injector data.
