SSpdDmon
April 11th, 2011, 06:10 AM
WARNING: RESEARCH INCOMPLETE - NO FINDINGS HAVE BEEN SOLIDIFIED. PLEASE DON'T TRY ANY OF THIS YET UNTIL I GET TIME TO VALIDATE RESULTS...UNLESS YOU KNOW EXACTLY WHAT YOUR DOING. LOL
So, I started playing around with some things in the tune today. One of the issues I've been curious about solving is - how to run closed loop with a big cam on a stock OS. The typical problem with bigger cams seems to be the overlap. If you have a good bit of unburnt oxygen traveling into the exhaust, it can confuse the hell out of the O2s causing them to tell the PCM, "Hey - you need to dump a lot more fuel in this motor 'cause you're f**kin' up right now." Next thing you know, your idle is extra rich and stinkin' up the garage, the parking lot, or the intersection.
Well, I got my tune pretty damn close in an OL MAF only (with OEM MAF curve) tune by adjusting my injector settings. This left me with an IFR that goes from roughly 32lbs/hr to 39.9lbs/hr for my SVO redtops. I adjusted the minimum pulse widths (including the new Transient Min PW) to roughly 1.07~1.08ms. Lastly, I altered the Voltage Adjustment based on some Ford PDF datasheet I found on the injectors online.
With this tune, I had awesome AFRs throughout pretty much all driving conditions. The WBO2 would read between 13.9~14.7:1 anytime I was on throttle and WOT was pretty much right on the money (had to tweak the top part of the MAF curve 1%). Idle was sitting around 17:1 on the WBO2, but I know I can't trust it. The car does idle nice and smooth (well, as smooth as it can for a nasty cam) without that overwhelming fuel smell it used to have. So, I'm fairly confident in where I have it set.
The next step was to re-enable closed loop. But, how will it not see the 17:1 at idle and freak out I asked??? Looking over the tables, there seems to be a clear set of parameters that distinguish idle STFTs from non-idle. Using this part of the tune, I zero'd out the STFT adjusters for idle (B4118, B4109, B4110) and tweaked the idle mode part of the tune for the trims (B4101=200, B4103=2%). In theory....with these settings....anytime I'm off throttle (less than 2%) and in closed loop, I should be in idle fueling mode. If I'm in gear and decelerating, DFCO kicks in pretty quick and cuts fuel anyway. So, that pretty much leaves coasting to a stop with the clutch in or sitting still.
So far, initial tests have looked promising. The short term fuel trims quit moving at idle. I was still seeing some LTFT correction making it through in the transitions though. My next test is to try zeroing out B3808, adjusting the RPM boundaries for the LTFT cells, and tweaking the delays/filters that allow the trims to move. I'll keep y'all posted... :)
So, I started playing around with some things in the tune today. One of the issues I've been curious about solving is - how to run closed loop with a big cam on a stock OS. The typical problem with bigger cams seems to be the overlap. If you have a good bit of unburnt oxygen traveling into the exhaust, it can confuse the hell out of the O2s causing them to tell the PCM, "Hey - you need to dump a lot more fuel in this motor 'cause you're f**kin' up right now." Next thing you know, your idle is extra rich and stinkin' up the garage, the parking lot, or the intersection.
Well, I got my tune pretty damn close in an OL MAF only (with OEM MAF curve) tune by adjusting my injector settings. This left me with an IFR that goes from roughly 32lbs/hr to 39.9lbs/hr for my SVO redtops. I adjusted the minimum pulse widths (including the new Transient Min PW) to roughly 1.07~1.08ms. Lastly, I altered the Voltage Adjustment based on some Ford PDF datasheet I found on the injectors online.
With this tune, I had awesome AFRs throughout pretty much all driving conditions. The WBO2 would read between 13.9~14.7:1 anytime I was on throttle and WOT was pretty much right on the money (had to tweak the top part of the MAF curve 1%). Idle was sitting around 17:1 on the WBO2, but I know I can't trust it. The car does idle nice and smooth (well, as smooth as it can for a nasty cam) without that overwhelming fuel smell it used to have. So, I'm fairly confident in where I have it set.
The next step was to re-enable closed loop. But, how will it not see the 17:1 at idle and freak out I asked??? Looking over the tables, there seems to be a clear set of parameters that distinguish idle STFTs from non-idle. Using this part of the tune, I zero'd out the STFT adjusters for idle (B4118, B4109, B4110) and tweaked the idle mode part of the tune for the trims (B4101=200, B4103=2%). In theory....with these settings....anytime I'm off throttle (less than 2%) and in closed loop, I should be in idle fueling mode. If I'm in gear and decelerating, DFCO kicks in pretty quick and cuts fuel anyway. So, that pretty much leaves coasting to a stop with the clutch in or sitting still.
So far, initial tests have looked promising. The short term fuel trims quit moving at idle. I was still seeing some LTFT correction making it through in the transitions though. My next test is to try zeroing out B3808, adjusting the RPM boundaries for the LTFT cells, and tweaking the delays/filters that allow the trims to move. I'll keep y'all posted... :)