Quick VE table question
Quick VE table question I finally got a good warm sunny weekend to do my SD tune. Well my LTFT's were around -10 to -16 It took a full day sat riding around to get them around -4 to -7. Ok now yesterday I went logging again since the temps were the same. Once I got them that low I was copying & pasting precentage instead of adding the cells to the VE table. They got a tad better now. Now that the LTFT's are that low it low RPMs the car acts like the fuel pump quits, I can start it & it will idle fine but as soon as you give it gas it trys to die & doesnt rev. Did I miss something or did I take to much from the VE table down low?
Thanks
Thanks
Originally Posted by foff667
you might want to serioiusly consider tuning with a wideband rather then trims in your car...just a suggestion.
Have you tweaked the cylinder volume data in the tune? That might cause an issue if you haven't.
I would suspect a mechanical (or sensor) issue rather than a VE issue. I've never seen a car run worse with a more accurate tune.
I would suspect a mechanical (or sensor) issue rather than a VE issue. I've never seen a car run worse with a more accurate tune.
Please post when you figure it out. I was having the same problems and the wideband read way lean when it starting reving up. Plugging in the maf totally corrected the problem, but couldn't get the sd working. Played with ve values and ifr table and still no luck.
Originally Posted by SMOKINV8
Have you tweaked the cylinder volume data in the tune? That might cause an issue if you haven't.
I would suspect a mechanical (or sensor) issue rather than a VE issue. I've never seen a car run worse with a more accurate tune.
I would suspect a mechanical (or sensor) issue rather than a VE issue. I've never seen a car run worse with a more accurate tune.
Its possible that you didn't log enough frames in the problem area to get a good ve value. If the problem goes away with your maf plugged in, it would probably be easy to overlay the graphs of dynamic airflow and maf airflow with the maf disabled (set the fail frequency to 0). Then you could easily see if the dynamic airflow is too low or too high when it happens.
What is your spark advance doing when this happens? Anything weird? Also don't A4 cars have issues with going mafless?
Also, I don't know if I read this right, but you didn't have issues before the FAST 90/90 combo? It could be possible that you have a vacuum leak. That would show up at low rpms and it would also make it impossible to tune from fuel trims.
What is your spark advance doing when this happens? Anything weird? Also don't A4 cars have issues with going mafless?
Also, I don't know if I read this right, but you didn't have issues before the FAST 90/90 combo? It could be possible that you have a vacuum leak. That would show up at low rpms and it would also make it impossible to tune from fuel trims.
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Originally Posted by 98A4LS1
You decreased the RAF values?
When my car was having those issues, after many miles/hours of logging the LTFT's were showing 10-13. I couldnt get them no lower than 9. By then I think I had already taken too much from the VE table. I would log, make the changes, copy the Primary to the secondary VE table then loaded, reset fuel trims then logged some more. When I first started they were around 16-17, so they did change but it took all day to get them down that low.
BTW- I also loaded the other tune back in then modifyed, I didnt use the one that I had been changing the VE table
This just doesn't sound right.
Are you sure you disabled/disconnected the MAF when you were trying to do your LTFT VE tuning? If you didn't, the LTFT's wouldn't change much when you were modifying the VE table, and eventually a low enough VE could cause the problems you describe.
If your MAF is connected you can get the car to run fine (for the most part) just by tweaking the MAF tables, but its not completely safe. Sharp throttle changes aren't going to be even remotely accurate with a combo like yours.
Are you sure you disabled/disconnected the MAF when you were trying to do your LTFT VE tuning? If you didn't, the LTFT's wouldn't change much when you were modifying the VE table, and eventually a low enough VE could cause the problems you describe.
If your MAF is connected you can get the car to run fine (for the most part) just by tweaking the MAF tables, but its not completely safe. Sharp throttle changes aren't going to be even remotely accurate with a combo like yours.
Originally Posted by SMOKINV8
This just doesn't sound right.
Are you sure you disabled/disconnected the MAF when you were trying to do your LTFT VE tuning? If you didn't, the LTFT's wouldn't change much when you were modifying the VE table, and eventually a low enough VE could cause the problems you describe.
If your MAF is connected you can get the car to run fine (for the most part) just by tweaking the MAF tables, but its not completely safe. Sharp throttle changes aren't going to be even remotely accurate with a combo like yours.
Are you sure you disabled/disconnected the MAF when you were trying to do your LTFT VE tuning? If you didn't, the LTFT's wouldn't change much when you were modifying the VE table, and eventually a low enough VE could cause the problems you describe.
If your MAF is connected you can get the car to run fine (for the most part) just by tweaking the MAF tables, but its not completely safe. Sharp throttle changes aren't going to be even remotely accurate with a combo like yours.
Now, I loaded the previous tune I had before I started VE tuning, the LTFTs were back around +16 as before. I keep multiplying the MAF tables by precentages till I found a good precentage where the LTFT's seemed to be close. What do you mean this is not safe? What do you suggest I do then? If you'd like I can send you the tune if you want to take a look at it. Just PM me your email address. Not sure if I still have the problem tune still saved or not. Ill have to check into that on.
Calling it, "Not safe," might not be entirely accurate, but not having an accurate VE leaves you open to lean (or rich) spots during quicker throttle changes. The nature of how a MAF works won't let it respond to quick throttle changes, so the PCM is set up so it references predetermined fueling values (VE table) which should provide the right amount of fuel when the MAF might not read right. Its part of the hybrid SD/MAF system that the PCM uses.
