Power FC A/F Tuning 101
09-28-03, 11:24 PM
#1
A/F Tuning 101
I have this subtle feeling that it's not very common to tune with the PFC and have your air pump still connected and working. I say this because I was experimenting with different fuel settings at idle and I made the startling, although not entirely non-intuitive discovery:
Your low-RPM A/F readings are worthless if the air pump is on!!!
I set up some watches on Datalogit and turned the air pump on and off by messing with the connector to the drive clutch. As I did this, the revs did not rise at all, but the A/F went from 14.3 to 18.8 nearly instantly. (18.8 is the max on my TE WBo2 v2.0) I've got the O2 sensor in the downpipe about 8-10 inches from the turbo exhaust flange.
After shutting off the pump I discover that I've been running really rich in the high vacuum/low RPM cells (P1-N1 through P7-N3). This may explain the backfires I've been getting when reving the engine with the car in neutral.
That said, I can't seem to get the car to idle smoothly yet--it's a little lopey sometimes. I'm going to keep playing with it, but I just couldn't believe that no one on the board has mentioned that tuning idle A/F with the air pump on is a waste of time.
It also makes me wonder how the hell the factory O2 sensor does anything useful at idle...
-ch
Your low-RPM A/F readings are worthless if the air pump is on!!!
I set up some watches on Datalogit and turned the air pump on and off by messing with the connector to the drive clutch. As I did this, the revs did not rise at all, but the A/F went from 14.3 to 18.8 nearly instantly. (18.8 is the max on my TE WBo2 v2.0) I've got the O2 sensor in the downpipe about 8-10 inches from the turbo exhaust flange.
After shutting off the pump I discover that I've been running really rich in the high vacuum/low RPM cells (P1-N1 through P7-N3). This may explain the backfires I've been getting when reving the engine with the car in neutral.
That said, I can't seem to get the car to idle smoothly yet--it's a little lopey sometimes. I'm going to keep playing with it, but I just couldn't believe that no one on the board has mentioned that tuning idle A/F with the air pump on is a waste of time.
It also makes me wonder how the hell the factory O2 sensor does anything useful at idle...
-ch
09-29-03, 12:56 AM
#2
Rotary Freak
I just found this out as well. I just got the LM-1 Wideband O2 and have been having some issues with it. The designer of the LM-1 says that you can't run the airpump while using the airpump at all. I also need to check the accuracy of the LM-1 against another WB. I'm not sure it's accurate.
As fot the shitty idle. You should do what I did. Let the PFC "learn" how to set your car's idle.
1. On the Commander: "Initialize all data" Once you select "yes". You have to key on and key off for it to take effect.
2. Let the car idle for 15 whole minutes, then 15 more minutes with the rear defroster on, then 15 more minutes with the a/c on.
3. Then re-enter your previous maps. Don't do a write-all because it may re-set what the PFC just learned.
Are you in NorCal? We should hook up. I need to learn how to tune also.
As fot the shitty idle. You should do what I did. Let the PFC "learn" how to set your car's idle.
1. On the Commander: "Initialize all data" Once you select "yes". You have to key on and key off for it to take effect.
2. Let the car idle for 15 whole minutes, then 15 more minutes with the rear defroster on, then 15 more minutes with the a/c on.
3. Then re-enter your previous maps. Don't do a write-all because it may re-set what the PFC just learned.
Are you in NorCal? We should hook up. I need to learn how to tune also.
Last edited by jpandes; 09-29-03 at 01:03 AM.
09-29-03, 01:20 AM
#3
J,
Thanks for the reset tip--I didn't know how to do that with the PFC. I'll try that one tomorrow...
My plan is to tune the car perfectly w/out the air pump and then try turning it back on and re-learning the idle. The lame part is that the WBo2 will read very lean until the damn pump switches off. I think it's a good idea to disable this whenever you're running hard (track) to ensure that you get valid logging.
It will be nice to see how the LM-1 and TE 2.0 stack up against each other!
Sent you a PM on the norcal thing...
-ch
Thanks for the reset tip--I didn't know how to do that with the PFC. I'll try that one tomorrow...
My plan is to tune the car perfectly w/out the air pump and then try turning it back on and re-learning the idle. The lame part is that the WBo2 will read very lean until the damn pump switches off. I think it's a good idea to disable this whenever you're running hard (track) to ensure that you get valid logging.
It will be nice to see how the LM-1 and TE 2.0 stack up against each other!
Sent you a PM on the norcal thing...
-ch
09-29-03, 05:53 PM
#4
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Originally posted by hyperion
My plan is to tune the car perfectly w/out the air pump and then try turning it back on and re-learning the idle. The lame part is that the WBo2 will read very lean until the damn pump switches off. I think it's a good idea to disable this whenever you're running hard (track) to ensure that you get valid logging.
My plan is to tune the car perfectly w/out the air pump and then try turning it back on and re-learning the idle. The lame part is that the WBo2 will read very lean until the damn pump switches off. I think it's a good idea to disable this whenever you're running hard (track) to ensure that you get valid logging.
09-30-03, 02:00 AM
#5
The air pump only runs up to 3200 rpm, you should hardly ever be that low at the track (excepting a super slow auto-x turn).
-ch
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