Dynamic Cylinder Air Chat
Thread Starter
TECH Addict
Joined: Feb 2004
Posts: 2,826
Likes: 0
Originally Posted by Silverhawk_02TA
I think the O2's themselves are fine. I would say it's probably an issue with the O2 signal processing circuit inside the PCM. I think this is also the reason your general O2 waveform looks so demented. Even one component a little bit out of tolerance in that circuit could cause issues, and with the complicated interdependencies of an electronic device as complex as the PCM, it's quite possible that plugging in the MAF results in an errant induced voltage or extra load that just pushes it over the edge.
The MAF airflow reading is independent of the IAT sensor reading. The DA calc relies heavily on the IAT, which makes SD operation very dependent upon it as well. IAT only indirectly affects MAF operation through the DA calc that's used to filter the MAF reading during throttle transients. Also, I've seen your logged IAT when your trims take a ****, and it is steady.
The MAF airflow reading is independent of the IAT sensor reading. The DA calc relies heavily on the IAT, which makes SD operation very dependent upon it as well. IAT only indirectly affects MAF operation through the DA calc that's used to filter the MAF reading during throttle transients. Also, I've seen your logged IAT when your trims take a ****, and it is steady.
I looked at the 14APR05.hpl file and it seems to me that the
O2s are kind of "soggy". I see very little change in the injector
PW despite gross changes in the STFT. I see the O2s swing up
and stick high with minimal change in air or fuel. The STFTs start
to accumulate negative "momentum" while the O2s are below
0.5V in some cases. This is just not sane.
This looks like behaviors I have seen in circuit designs where
a closed loop is being driven outside linear operation, saturates
& relaxes back, all on a timescale well outside the designed
stabilization frequency corners.
Did you mess around the proportional O2 stuff? I wonder if the
filter params might have changed to some values that destabilize
the loop?
Still I don't see why that would have a MAF/SD dependence,
other than that the two tunes might be differently mixture
biased and one might avoid the "trouble spot" by being leaner
or richer?
O2s are kind of "soggy". I see very little change in the injector
PW despite gross changes in the STFT. I see the O2s swing up
and stick high with minimal change in air or fuel. The STFTs start
to accumulate negative "momentum" while the O2s are below
0.5V in some cases. This is just not sane.
This looks like behaviors I have seen in circuit designs where
a closed loop is being driven outside linear operation, saturates
& relaxes back, all on a timescale well outside the designed
stabilization frequency corners.
Did you mess around the proportional O2 stuff? I wonder if the
filter params might have changed to some values that destabilize
the loop?
Still I don't see why that would have a MAF/SD dependence,
other than that the two tunes might be differently mixture
biased and one might avoid the "trouble spot" by being leaner
or richer?
Thread Starter
TECH Addict
Joined: Feb 2004
Posts: 2,826
Likes: 0
Originally Posted by jimmyblue
I looked at the 14APR05.hpl file and it seems to me that the
O2s are kind of "soggy". I see very little change in the injector
PW despite gross changes in the STFT. I see the O2s swing up
and stick high with minimal change in air or fuel. The STFTs start
to accumulate negative "momentum" while the O2s are below
0.5V in some cases. This is just not sane.
This looks like behaviors I have seen in circuit designs where
a closed loop is being driven outside linear operation, saturates
& relaxes back, all on a timescale well outside the designed
stabilization frequency corners.
Did you mess around the proportional O2 stuff? I wonder if the
filter params might have changed to some values that destabilize
the loop?
Still I don't see why that would have a MAF/SD dependence,
other than that the two tunes might be differently mixture
biased and one might avoid the "trouble spot" by being leaner
or richer?
O2s are kind of "soggy". I see very little change in the injector
PW despite gross changes in the STFT. I see the O2s swing up
and stick high with minimal change in air or fuel. The STFTs start
to accumulate negative "momentum" while the O2s are below
0.5V in some cases. This is just not sane.
This looks like behaviors I have seen in circuit designs where
a closed loop is being driven outside linear operation, saturates
& relaxes back, all on a timescale well outside the designed
stabilization frequency corners.
Did you mess around the proportional O2 stuff? I wonder if the
filter params might have changed to some values that destabilize
the loop?
Still I don't see why that would have a MAF/SD dependence,
other than that the two tunes might be differently mixture
biased and one might avoid the "trouble spot" by being leaner
or richer?
Thread Starter
TECH Addict
Joined: Feb 2004
Posts: 2,826
Likes: 0
Update: I have eliminated FRA! as the culprit. Going back to my logs, I can't really figure what it could be. I am pretty much down to either the PCM or the MAF. Does the MAF do anything funny, or supply an signal other than the MAF frequency that would make the MAF bad? I really need a stocker to eliminate that as the problem.
edit: Well apparently the MAF only puts out a frequency signal based on what it reads, so if the frequency is not changing when the trims drop, it can't be a bad MAF. Oh well.
I don't get it. Anyways, I just eliminated the PCV as the problem also.
edit: Well apparently the MAF only puts out a frequency signal based on what it reads, so if the frequency is not changing when the trims drop, it can't be a bad MAF. Oh well.
I don't get it. Anyways, I just eliminated the PCV as the problem also.
Last edited by Another_User; May 15, 2005 at 09:10 PM.
Thread Starter
TECH Addict
Joined: Feb 2004
Posts: 2,826
Likes: 0
I don't know if anybody cares, or has any other input, but I have eliminated the MAF as the culprit as well. So basically, I have eliminated:
1) MAF (borrowed one from a friend, same result)
2) COT
3) EVAP
4) PCV
5) MAF Table
6) VE Table
7) O2 Sensors
Soooo....should I do a complete reflash of the PCM? The only things left are PCM and electrical issue to the MAF.
1) MAF (borrowed one from a friend, same result)
2) COT
3) EVAP
4) PCV
5) MAF Table
6) VE Table
7) O2 Sensors
Soooo....should I do a complete reflash of the PCM? The only things left are PCM and electrical issue to the MAF.
Last edited by Another_User; May 28, 2005 at 12:03 PM.
When building your VE tables, make sure you turn off everything!! I mean your air pump, so pull the fuse on it, turn off COT, turn off DEFCO also. All these factors will screw with your VE table building. Hope this helps. Maybe you have already, but just in case. you havent yet, try it.
Rick
Rick
Thread Starter
TECH Addict
Joined: Feb 2004
Posts: 2,826
Likes: 0
Originally Posted by Rick@Synergy
When building your VE tables, make sure you turn off everything!! I mean your air pump, so pull the fuse on it, turn off COT, turn off DEFCO also. All these factors will screw with your VE table building. Hope this helps. Maybe you have already, but just in case. you havent yet, try it.
Rick
Rick
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
