Matt:
Yup. I am very meticulous about bolt checks and triple checking that everythign is tightened down after a heat cycle or two. That's kinda built into who I am, and I have a pre-race event check list where I make sure I do my specific bolt checks, headers and exhaust has always been on the list. I agree wit hyou about if I was losing fuel pressure it would read lean. However, al that happens is usually a lean spike and then the CL comp sees this little spike and goes crazy adding tremendous amounts of fuel. There is indeed somethign interesting/confusing I noticed on pass #5, which I will post below, because the AFR was RICH at 10.0 and hte CL comp was going nuts adding fuel anyways. See below. I agree with you about limiting learn and CL comp amounts. I had everythign locked down pretty good last year to where the CL comp could only take away 10% of fuel and could only add 25% fuel across the whoel table on all of my drag-race based tunes. This seemed to work out well. I was told that this is wise, but a smarter decision would be to have the Cl comp be able to add 100% but only take away about 10-20%. Reason being, in case a mechanical problem actually really did happen, the computer could save the engine by adding fuel quicker than I could come off the pedal or turn off the engine. That made sense to me, but it might have opened the floodgates (literally) for the CL comp to start doing whatever it wanted to do, including adding massive amounts of fuel for an unknown reason.
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Larry: yes, glad I wasn't thinking incorrectly about that aspect of it. So, since I see almost NO Cl comp added at the top of gears 2 and 3, especially while at WOT, I am pretty confident that it is not a fuel system or fuel delivery issue. Some of the guys on the Holley forum are telling me its fuel system related, and I will investigate this aspect as much as I can, but I am still thinking it is tune, ecm, sensor, related. Same thinking as you regarding that O2 sensor being wonky. I would think that in the course of the last 5 weeks of driving the car, 3 drag race days, and whatnot, the O2 symptoms would be more prevalent than just simply acting up at Island dragway in a drag launch. I would see all sorts of wonky readings at various times. basically my learn table would look insane after simply driving the car a distance (like to and from Englishtown a few weeks ago), yet the learn table was super clean and low numbers, low enough that I never even decided to transfer the info to the base table. I am going to do my best to carve out some time to really dig into the datalogs and turn on every available sensor/parameter in each view-page and see if I can find this blip. If it is there, that will be the smoking gun.
Brian:
I had a completely full tank. The Shell gas station just half a mile away from Island Dragway is now open and I fueled up the whole tank with 93. I always make sure I have a full tank or as close to it as possible. I've never been of the thought that I can save a few pounds of weight and run a half tank of fuel. This became apparent to me back in 2017 at the Optima Street-car challenge when I was doing autocross and speed stop laps and my tank was low and for sure it was starving the old engine. I have always seemed to have either a rich or a lean spike at the hit whenever I launch. Since I am always leaving either at idle or a 1500-1800 rpm foot brake, and it is TBI so no injectors per cylinder, it has done both lean and rich spikes. I spend a lot of time refining the base table in this area, and I can only do so to a certain extent, without it getting screwed up during the burnout when it hits those same cells in the base table. Also, sadly, the Sniper software can not log fuel pressure. My mechanical analog gauge can, but that is under the hood. Testing of it over the winter showed it to be at 61-62 psi and the sniper's internal regulator likes fuel pressure at 59.5 psi, but they say give or take a few psi is fine. As for volts, my Holley reads low. It is wired directly to the battery with 10 gauge wire. When the battery reads 12.2 and the car is off, the sniper reads 11.9 or 11.8. On the datalogs, the battery trace is very consistent, yet numerically low at 13.3 volts...but it has been this way for every datalog in the last 14 months. The alternator is a powermaster unit and it is only a few years old. If you guys would like I can enable the battery trace on any datalog and show ya that it only drops by 0.1 and at most 0.2 volts at the hit of the throttle.
Pass 5:
This would stink if it was a failing injector or the like. Yet, I keep coming back to the clean Open Loop datalogs. But last night I did take notice of something on a closed loop pass, Pass #5, between 36 seconds & 39 seconds, which is when I launch.
What do you make of this situation:
- I had a fully cleared out Learn Table, all 0.0 numbers on there.
- Base tune is very solid and has been used many times prior.
- I footbrake launch from 1530 RPM and AFR goes rich, never does it spike lean.
- It goes immediately into Closed Loop and gets rich to about 10.0 AND then at the same exact time CL Comp comes in ADDING fuel. First at +4% then at +14%.
- AFR somehow gets less rich at 10.7, but the CL Comp is now +23%.
- AFR finally gets to Target AFR, but now the CL Comp is at an insane +57%.
- I feel the engine bogging, and I get out of it just at the same split second that the AFR now finally gets actually lean, at 14.7, and at this moment the CL Comp is +77%.
Why would CL Comp add tons of fuel if it's already reading a rich mixture? If as you said, fuel pressure is not at 60, well maybe that could so it, but is there a chance this is all an intermittent Closed Loop EFI problem and not a mechanical issue? There were no lean spikes until I got off the throttle. That makes no sense whatsoever to me. Anyone?
Datalog Screenshot:
