anybody have problems running less than 1/8 tank in F-Body?
10-14-2006, 11:18 PM
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anybody have problems running less than 1/8 tank in F-Body? It wasn't planned but on my last run of the day, My 99 SS drifted 1/2 point lean in 4th which caused knock and 3.5* of knock retard and ruined my top end. I had just under 1/8 tank, I would have rather had 1/4 but I'm new to F-bodys, does the way the sump is on these things allow it to slip air if you run at the track with less than an 1/8th? Christ the gauge was reading just under 1/4 before I drove it on the trailer so I was pissed when it was at 1/8th when I pulled to the staging lanes? WTF? The first run wasn't an issue the last run, when it displayed under 1/8th it seemed to nose over?
anybody else get bit by this?
anybody else get bit by this?
10-15-2006, 02:55 AM
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yea i have noticed it on mine playing around in town and such. if it gets around <1/8 it will kinda spudder a little in all the wrong places. i happened to catch it before i ever ran it at the track that low though.
10-16-2006, 08:23 PM
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I figured out my problem, it wasn't the gas level even though after hearing you guys I won't be running with less than 1/4 to 1/8+ ever again. The car never bucked, just went 1/2 point lean in the middle of 1/4 gear, started a perfect 13.0 and then went to 13.5 which caused some knock retard because I had the timing setup at the max (28.5) for 13.0 and good gas.
I went back for my last day at the track the next day and had a full 1/4+ with some higher octane unleaded Torco mix added and not only did it lay over again, it started to do it for the first part of 3rd and all of 4th. The problem was the air was so dry and the pressure so high, the mine shaft air let the MAF see more volume than it had the previous week and all the test passes I had run to calibrate the MAF. well VE correction factor was kicking in because I hadn't increased the VE tables to match the higher flow the MAF was seeing with a new K&N, SLP lid and SLP bellows so the computer thought it was out of bounds and started using the VE tables which thought there should be less air, gave less fuel and the AFR jumped up a 1/2 point.
I am new to the "GM" way, I tuned with a MAF for the track before and love the way it corrects for whatever air you are seeing, good or bad but I guess GM has it's own method and I need figure it out for consistency at the track. I read that only the MAF was used over 4K so I only corrected the VE table for STFT's in closed loop/MAF for WOT, that was obviously wrong, it prefers to use the MAF but can start using the VE tables if it feels like it! I also thought that some kind of average was used to eliminate spikeyness, Christ it looked like my AFR fell off a table it was so abrupt so that was wrong too. I smoothed in a correction to the VE tables in the high MAP pressure/ high RPM area by 2.5% (13.5/13.0) and also changed some of the thresholds so it will make that decision a little less quickly and correct less in the future.
What pisses me off is I had to deal with my car going SLOWER in the good air, right when I was running for money in a Gamblers race and wasted a .007 Elimination light when I couldn't figure out what the heck the car was going to run. I used the last couple passes of the day to test the VE table correction and basically start over trying to get a flat solid 13.0 AFR, like it had when it was only using the MAF but couldn't even get close to my 13.04 best ET, what a F'ng waste of good air.
I went back for my last day at the track the next day and had a full 1/4+ with some higher octane unleaded Torco mix added and not only did it lay over again, it started to do it for the first part of 3rd and all of 4th. The problem was the air was so dry and the pressure so high, the mine shaft air let the MAF see more volume than it had the previous week and all the test passes I had run to calibrate the MAF. well VE correction factor was kicking in because I hadn't increased the VE tables to match the higher flow the MAF was seeing with a new K&N, SLP lid and SLP bellows so the computer thought it was out of bounds and started using the VE tables which thought there should be less air, gave less fuel and the AFR jumped up a 1/2 point.
I am new to the "GM" way, I tuned with a MAF for the track before and love the way it corrects for whatever air you are seeing, good or bad but I guess GM has it's own method and I need figure it out for consistency at the track. I read that only the MAF was used over 4K so I only corrected the VE table for STFT's in closed loop/MAF for WOT, that was obviously wrong, it prefers to use the MAF but can start using the VE tables if it feels like it! I also thought that some kind of average was used to eliminate spikeyness, Christ it looked like my AFR fell off a table it was so abrupt so that was wrong too. I smoothed in a correction to the VE tables in the high MAP pressure/ high RPM area by 2.5% (13.5/13.0) and also changed some of the thresholds so it will make that decision a little less quickly and correct less in the future.
What pisses me off is I had to deal with my car going SLOWER in the good air, right when I was running for money in a Gamblers race and wasted a .007 Elimination light when I couldn't figure out what the heck the car was going to run. I used the last couple passes of the day to test the VE table correction and basically start over trying to get a flat solid 13.0 AFR, like it had when it was only using the MAF but couldn't even get close to my 13.04 best ET, what a F'ng waste of good air.
