Some questions about SD tuning
02-16-2005, 10:01 AM
#1
Some questions about SD tuning I have read quite a bit on here about SD tuning, but a few things still aren’t clear to me.
1. I understand that while SD tuning, you unplug the MAF, disable PE mode and you also set the targeted A/F ratio to 13.0:1 (so you are safe to tune in the upper RPM ranges, outside of PE mode). But what I don’t understand is that when you make adjustments to your VE Table while commanding a 13:1 A/F ratio, aren’t you just adjusting the table to be correct for maintaining the targeted 13:1? If so, what happens when you’re done tuning and you change your targeted A/F ratio back to stoich? Doesn’t this put you right back into negative trims again? Maybe what I’m missing is that you pretty much NEED to have a wideband to SD tune, and you are tuning your VE table to 14.7:1 (based on the WB input), even thought the PCM is trying to maintain 13:1. Is that correct?
2. Next, is it safe to look at the MAF input as a correction factor that is making sure the MAP sensor is seeing the correct amount of incoming air? In other words, is the main fueling based on the Main VE table (based on MAP sensor input and RPM) and then supplemented or “corrected” based on input from the MAF?
3. Finally, if the above is true, is WOT fueling based on the main VE table, plus the “adder” from the PE vs RPM table?
Any help with these questions would be much appreciated. Like I said, I read and search on here as much as I can, but sometimes, conflicting posts from different people confuse me. Thanks.
1. I understand that while SD tuning, you unplug the MAF, disable PE mode and you also set the targeted A/F ratio to 13.0:1 (so you are safe to tune in the upper RPM ranges, outside of PE mode). But what I don’t understand is that when you make adjustments to your VE Table while commanding a 13:1 A/F ratio, aren’t you just adjusting the table to be correct for maintaining the targeted 13:1? If so, what happens when you’re done tuning and you change your targeted A/F ratio back to stoich? Doesn’t this put you right back into negative trims again? Maybe what I’m missing is that you pretty much NEED to have a wideband to SD tune, and you are tuning your VE table to 14.7:1 (based on the WB input), even thought the PCM is trying to maintain 13:1. Is that correct?
2. Next, is it safe to look at the MAF input as a correction factor that is making sure the MAP sensor is seeing the correct amount of incoming air? In other words, is the main fueling based on the Main VE table (based on MAP sensor input and RPM) and then supplemented or “corrected” based on input from the MAF?
3. Finally, if the above is true, is WOT fueling based on the main VE table, plus the “adder” from the PE vs RPM table?
Any help with these questions would be much appreciated. Like I said, I read and search on here as much as I can, but sometimes, conflicting posts from different people confuse me. Thanks.
