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#51102
I'm having an issue where two different engine runs will have vastly different results. The attached log files show an example. One run is fine, tracking well to AFR values while the other the car ran rich. After going through the logs, it looks like the rich run had a greater pulse width (PW) value for the same conditions. This is easiest to see at idle where the normal file shows ~1.8 while the rich file shows ~1.9. Gamma is consistent at 100%, EGO is off, and MAP is reading the same.

So I guess the question is: What goes into the PW calculation that could change the value from one run to the next if it's not gamma or MAP?

Any help is much appreciated.
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Last edited by SomeYahoo on Thu Jun 17, 2021 2:35 am, edited 1 time in total.
#51107
You are using the Multiply VE in Baro mode. Your Baro is 95kpa in one log and 85kpa in another. That's where your difference comes from. Don't know if your barometric pressure actually has changed that much between the drives. But I prefer running Multiply VE in fixed mode and then the baro reading is not messing with AFR anymore. Then if bar correction is really needed, have separate baro sensor and use the baro correction curve.
#51108
pazi88 wrote:
Wed Jun 16, 2021 5:46 am
You are using the Multiply VE in Baro mode. Your Baro is 95kpa in one log and 85kpa in another. That's where your difference comes from. Don't know if your barometric pressure actually has changed that much between the drives. But I prefer running Multiply VE in fixed mode and then the baro reading is not messing with AFR anymore. Then if bar correction is really needed, have separate baro sensor and use the baro correction curve.
Thanks much for this, I never would have looked for that since I don't even have a baro sensor. Wonder where it got that data from? I'll give it a shot in fixed mode.
#51110
SomeYahoo wrote:
Wed Jun 16, 2021 10:35 am
pazi88 wrote:
Wed Jun 16, 2021 5:46 am
You are using the Multiply VE in Baro mode. Your Baro is 95kpa in one log and 85kpa in another. That's where your difference comes from. Don't know if your barometric pressure actually has changed that much between the drives. But I prefer running Multiply VE in fixed mode and then the baro reading is not messing with AFR anymore. Then if bar correction is really needed, have separate baro sensor and use the baro correction curve.
Thanks much for this, I never would have looked for that since I don't even have a baro sensor. Wonder where it got that data from? I'll give it a shot in fixed mode.
It takes the baro reading from map sensor before engine is running and uses that. But there is possibility for error in that method. (like if the ecu resets while engine is running). ¨

BTW When you switch to "fixed" mode, the VE map probably require re-tuning.
#51111
pazi88 wrote:
Wed Jun 16, 2021 11:35 am
SomeYahoo wrote:
Wed Jun 16, 2021 10:35 am
pazi88 wrote:
Wed Jun 16, 2021 5:46 am
You are using the Multiply VE in Baro mode. Your Baro is 95kpa in one log and 85kpa in another. That's where your difference comes from. Don't know if your barometric pressure actually has changed that much between the drives. But I prefer running Multiply VE in fixed mode and then the baro reading is not messing with AFR anymore. Then if bar correction is really needed, have separate baro sensor and use the baro correction curve.
Thanks much for this, I never would have looked for that since I don't even have a baro sensor. Wonder where it got that data from? I'll give it a shot in fixed mode.
It takes the baro reading from map sensor before engine is running and uses that. But there is possibility for error in that method. (like if the ecu resets while engine is running). ¨

BTW When you switch to "fixed" mode, the VE map probably require re-tuning.
Ah, that makes sense. Wonder if I started cranking before it took a reading or something. Figured the turn would need tweaks, but I'm still in tuning mode so that's no issue.

Thanks!
#51115
Good detective work. 8-) I am the opposite, and always use baro, either on startup or real-time. The benefits are significant from my perspective. However, @pazi88 is correct that it can be erroneous if there are issues in your system causing it. Of course, there are several functions that can be corrupted or misread, and baro is only one of them. None are acceptable. I correct the issues and enjoy the benefits.

In-fact, on first-read systems like ours, I would shift into neutral and kill the engine while coasting, in order to get a new baro reading on restart for my current weather and altitude. This would bring fueling back towards tuned values with less latent correction. If you want to fix the baro, that's fine, and you know how. If you want to use it, then be sure your ECM does not have any issues, including any that would corrupt the baro reading. ;)
#51128
Rock on! Image If you notice your tune is not stable, and the EGO corrections are working a lot, look back into this issue. The better it's tuned, the more you will notice it. Baro is not just for obvious altitude change, but for common daily stuff like weather conditions (density altitude).

EGO is a reactionary correction, so it lags behind. The effect is that it's down on power and response, and never quite runs "right", except at that same baro pressure it was tuned-at. The ECM has a lot to deal with from variable fuel supply to swings in temperature, humidity, voltages, and more. The less you force it to correct, the better and more consistently it will run. Have fun!

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