Is it possible the VVE coefficient calculator is making a mistake? ZR1 SD issue
Hi all,
I'm running into a problem where the vve table looks very smooth in the area of concern but there is still an issue when making a pull on the dyno. Each time I make a dyno run, there is a blip in calculated VE airflow causing cyl air mass to drop (making fuel drop and timing go up). This can be felt as an extremely short hiccup in the car and I can't figure out how to solve it. Has anyone run into this and can anyone offer some feedback? Attaching both the tune and log. Problem happens at 20.5 seconds into the log. You can see that the VE channel drops right there. I assume that is the cause of the issue.
your way above the computer estimate max kpa of 190 change it to read higher than 190. Second on your VVE click row axis edit select default select middle and you will see the whole in your ve table sorry the thumbnails always post sideway no matter what way i set them. Go to airflow general under map estimated max raise it higher than what your readings of 239 kpa and change under engine diag max airflow vs rpm double it and see if it helps i attached a smoothed ve between horizontal bounds. This should not throw off your fuel but get rid of your glitch. zr1's read above 105 kpa you have tune above it as well. very different from zl1 you have to tune up to the last kpa boundary and in sd mode its whatever kpa you hit. There is a third default row but you wont need it. Your going to have to expand your data logging histograms.
thank you for the response but I'm not sure I understand your explanation. Why would I change to the default middle row when it has a max kpa of only 200,and my application runs up to 235 kpa? The hole in the graph is known, but it is at 130kpa, while the problem is happening at 230kpa in the log. Can you explain what the "max expected kpa" does ? I've seen it many times but this car has run flawlessly on maf for years at 700whp with that parameter set at 190.
this is hard to explain. For some reason i've found that above the last kpa line if you change anything in vve between the last 2 map kpa and the transitions aren't smooth boundaries it has an effect on calculations up high. Remeber we dont actually have a ve chart so the math is essentially estimated. If I change a number anywhere from the 105 to the last 135 kpa boundary it effects the end calculation. Its a combination of our predicted coefficients and the way out computers do math. The max expected kpa means after that kpa it wont read anything on the sd chart higher that the 190 line so that can also be your problem. essentially your fueling might only be reading the 190kpa line
see ive found that a combination of the end 2 zones on my zl1 do the same thing. Mine are set lower but if i change anything from the last 2 boundaries it effects the curve or the rest or the map kpa above the last line. picture it like change the angle of the last zone it essentially changes the angle of the rest of the VVE. Its a quirky thing ive run into overdriving these blowers. I had a ve coefecient jump from 20-40 and it was exaclty like yours the car even ran fine too but it was a dimple in the lower boundary. It had nothing to do with the end boundary. are those stock injectors cause i see a higher flow rate on yours??? need to be logging afr and fuel pressure too. you might actually have detonation too. Possible misfire. Add misfire counter to your charts. see if you can get a misfire count. theres an actual drop in kpa makes me think might not just be vve try smoothing the ve first and after your done right entire ecu then disconnect battery to clear any keep alive memory in the ecu. Ive had glitches after writes like o2 sensors refusing to switch and had to disconnect battery. dumb things like abs and steering codes that my snap on scanner wouldnt clear. Yes a 5000 dollar snap on scanner.
i say try settings and write and disconnect battery to clear KAM.
if it doesnt stop doing it the check misfire counter and fuel pressure
also you realize your maf is disabled right???? why change now ?
also if your changed your injectors who forgot to change the offset vs press vs kpa table theres misssin data the more i look the more i see the offset to injector temp should be set to zero so you dont run 10 percent rich for 20 minutes after every reflash. The zr1 and zl1 injectors were the same so your flow rate being higher without the offset table being changed is why you had to keep taking fuel out with maf the higher you went. Ive read about dozen tunes where guys forget to do this with the id850 injectors and the maf curve vs stock goes down instead of up cause injector offset tables were never set. you got away with it with maf cause it blended the calculation in and now you take the maf out and you dont have the correct offset data. Unless someone just decided to change the injector data but i doubt it. I need to know all mods so we can figure this out. also gm stock operating isnt designed to be run in sd mode continuously. it requires maf calculations at all times. people think below a certain rpm maf doesnt have any play but this isnt true. It holds less on fuel trims. Thats why if you do maf fail mode the car doesnt idle as smooth. If i disable my maf my car wont idle as clean and its not set to enable until 2300 rpm. it does play a role more than most think.
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