12212156 + Big Cam

[SSpdDmon]

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...

[WeathermanShawn]

Hi Jeff:

Interesting..

When you say 'Big cam', what kind of overlap parameters you talking about?

[SSpdDmon]

Hi Jeff:

Interesting..

When you say 'Big cam', what kind of overlap parameters you talking about?

Not 100% sure on the cam specs. Still waiting on them from the previous owner. I'm under good suspicion that this thing is in the 240's likely on a 112. I know my 232/238 cam from 2 cars ago had some decent overlap that created a similar problem. My guess is, we're talking somewhere over 10 degrees at least - more likely closer to 20 degrees.

[joecar]

Hi Jeff,

Yes, that is correct, the NBO2 will see unburnt oxygen and register lean.

so you're looking to disable CL trimming while in idle mode...?

[SSpdDmon]

Hi Jeff,

Yes, that is correct, the NBO2 will see unburnt oxygen and register lean.

so you're looking to disable CL trimming while in idle mode...?

Yes. I've gone as far as I can for now with testing this (over lunch and after work today). I've got another issue that's getting in the way. The speedo isn't getting a clear signal from the trans. I'll look at the dash while cruising down the road and it'll sometimes read right, sometimes read 0, and sometimes it's having a siezure. In my head (assuming all of the descriptions are accurate), I think I've zero'd out the right things. I just need the car to realize when it's actually stopped.

The other thing I was going to try was to kill the LTFT's based on the CL Mode (referenced by airflow). Anything under 16 grams/sec of airflow doesn't need trimming IMO. So, I might take a crack at a few of the other tables. But, not until I get this damn speedo to read right.

Any other suggestions?

[voda1]

Anything new to report?

[SSpdDmon]

No...been quite busy this summer and haven't had much time to keep going with this. Thinking of leaving it in OL for a while.

[maudyZ28]

just read through this thread. Although my cam is only 228/228 it's on a 112 LSA 110ICL I think, with 4 deg overlap. I've got idle 'ok' i suppose and it runs nice at closed loop but does smell rich using O2's to trim (WB fluctuates around 14.7 as expected). It did run ok in MAF only Open loop but WB read about 13.2 all the time. Could I use a CO gas analyser to set idle up better?

[SSpdDmon]

With only 4 degrees, it might not be as big of a deal. I finally did the math on mine and I think it came out to like 18*. If it was running rich on the WB while MAF only, then either the MAF curve, the IFR, or both were likely off a touch. At least, that's usually the case that I've found.

[maudyZ28]

thanks for reply. Well running MAF only to tune it in gear it was spot on 14.7 as commanded but out of gear it would be 13.2 AFR ( i assume IFR is correct as it is from Z06 and i'm using those injectors) VE and MAF everywhere else is good. Maybe just need to tune at idle more when car is warm but not too warm?

Running MAF only, the car stalls 70% of the time going into gear with no gas. I'm wondering if I need to mess with desired airflow some more. I'd been advised to look at a HSV tune and this had a lot more desired airflow out of gear than in. I wanted to get everything consistent but worried now i may have to fudge/guess lower MAF parameters to get the car runnning nice. The idea to set it up, add 2% to calibration then enable CL so trims pull fuel but PE will be dialed in spot on and run 'perfect' everytime