R/L Threshold voltage
08-17-2002, 10:02 AM
#1
R/L Threshold voltage
7747 TBI ECU, running MFPI injectors:
Why does the R/L threshold voltage (and the Rich and Lean values as well) at the higher airflow numbers hinge on 391mV instead of the 450mV switch point of the O2 sensor??? Why are they not at 450mV??? Would raising them to 450mV make the engine richer? I think not as this is just really a "switch" function and the switch would essentially occur at the same time as it is so fast...
I am in the middle of re-installing my 7747 ECU for control and curious as heck. PROM eraser came yesterday. Ready to start a-burnin'!!!
Why does the R/L threshold voltage (and the Rich and Lean values as well) at the higher airflow numbers hinge on 391mV instead of the 450mV switch point of the O2 sensor??? Why are they not at 450mV??? Would raising them to 450mV make the engine richer? I think not as this is just really a "switch" function and the switch would essentially occur at the same time as it is so fast...
I am in the middle of re-installing my 7747 ECU for control and curious as heck. PROM eraser came yesterday. Ready to start a-burnin'!!!
08-17-2002, 10:20 AM
#2
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Re: R/L Threshold voltage
Originally posted by fast_broker
7747 TBI ECU, running MFPI injectors:
Why does the R/L threshold voltage (and the Rich and Lean values as well) at the higher airflow numbers hinge on 391mV instead of the 450mV switch point of the O2 sensor??? Why are they not at 450mV??? Would raising them to 450mV make the engine richer? I think not as this is just really a "switch" function and the switch would essentially occur at the same time as it is so fast...
7747 TBI ECU, running MFPI injectors:
Why does the R/L threshold voltage (and the Rich and Lean values as well) at the higher airflow numbers hinge on 391mV instead of the 450mV switch point of the O2 sensor??? Why are they not at 450mV??? Would raising them to 450mV make the engine richer? I think not as this is just really a "switch" function and the switch would essentially occur at the same time as it is so fast...
The ecm will always hunt around the commanded AFR, with those you controll how lean and how rich it goes.
08-17-2002, 11:54 AM
#3
So, Grumpy, raising the values WILL truly slightly richen up the mixture while in closed loop. Also, the calculated AFRs while in Open Loop will be slightly effected as well, and be slightly richer? I am under the belief that the ECU hunts to make the O2 sensor swing about that switch point (R, R/L, L thresholds) and you TELL the ECU that this point is 14.7 so it can make its OPEN loop calcs.
Another question on Proportional Duration Term vs O2 error:
Seconds, ASDZ 7747 PROM
0.03 little error
0.05
0.08
0.08
0.10
0.13
0.20 mod error
0.30
0.60
1.20
2.40
6.00
6.00 lots of error
Q) Are the BPW changes (from the prop Gain calculations) used for the ENTIRE prop Duration Terms above, or is the duration "stopped" when, say, the rich/lean flag is changed? ie: How can any prop change last for 6 seconds on a large O2 error????? That's a million years to an engine???
Another question on Proportional Duration Term vs O2 error:
Seconds, ASDZ 7747 PROM
0.03 little error
0.05
0.08
0.08
0.10
0.13
0.20 mod error
0.30
0.60
1.20
2.40
6.00
6.00 lots of error
Q) Are the BPW changes (from the prop Gain calculations) used for the ENTIRE prop Duration Terms above, or is the duration "stopped" when, say, the rich/lean flag is changed? ie: How can any prop change last for 6 seconds on a large O2 error????? That's a million years to an engine???
08-20-2002, 03:44 PM
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Originally posted by fast_broker
So, Grumpy, raising the values WILL truly slightly richen up the mixture while in closed loop. Also, the calculated AFRs while in Open Loop will be slightly effected as well, and be slightly richer? I am under the belief that the ECU hunts to make the O2 sensor swing about that switch point (R, R/L, L thresholds) and you TELL the ECU that this point is 14.7 so it can make its OPEN loop calcs.
So, Grumpy, raising the values WILL truly slightly richen up the mixture while in closed loop. Also, the calculated AFRs while in Open Loop will be slightly effected as well, and be slightly richer? I am under the belief that the ECU hunts to make the O2 sensor swing about that switch point (R, R/L, L thresholds) and you TELL the ECU that this point is 14.7 so it can make its OPEN loop calcs.
When in closed loop the ecm toggles across 14.7 in an effort to maintain a 14.7 AVERAGE....
It will stry to maintain a 14.7 reguardless what numbers you enter. If you want to change the AFR you have to change the commanded AFR.
What will change is the extremes that the ecms toggles thru to acheive the commanded AFR.
You lost me on the other stuff is why no comment.
08-23-2002, 01:02 PM
#6
now I am totally confused:
I thought that the millivolt threshold numbers in the Rich, R/L and Lean threshold tables are assigned as the O2 sensor’s inherent “switching stoichiometric” values, which do not change for typical O2 sensors. In closed-loop, the ECU constantly adjusts the injector pulse width to get the O2 sensor output values to be in that “switching stoichiometric” range of O2mV values, say 430 - 460mV. Now the ECU knows you are at stoichimety (you told it to with the mV values) but it does not kow what this AFR value is. So, you also must ASSIGN a CALCULATING stoich value (say, 14.7 in typical cases) to this stoichiometric switching O2value which the ECU ONLY USES in Open Loop calcs, like cold start up and PE enrichment.
To expand on possible changes, you could have an O2 sensor with different mV switching values (like a Wide band O2, for instance) and/or you could have a fuel/air mixture that does not have a 14.7:1 AFR value, like diesel fuel, which is about 18 AFR for arguments sake. So, if the WB O2 sensor switching mV values in the diesel application were 700 – 800mV and we know that the diesel fuel wants an 18:1 AFR, you set the R, R/L and L tables to straddle the 700 – 800mV range and set the calc “stoich” to 18 (instead of the 14.7 for regular fuel).
To wit, if running regular fuel/regular O2, if you tell the ECU that STOICH is 13 and do not change the mV threshold values or any of the OL AFR values, the result will be that the OL actual AFR seen by the engine will be leaner but closed-loop operation would not change whatsoever. If STOICH is labeled as 13.0 and PE enrichment is 13 at all points, the open loop calcs will result in a "truly" stoichiometric AFR at the spark plug as they happen to match in this case.
ie, the ECU doesn't toggle around "14.7" while in closed loop, it toggles the BPW to get the O2 readings around the R, R/L, L threshold mV values that you supply.
In other words, the 14.7 stoich value is NEVER NEVER used in closed loop operation, whatsoever, but is the assigned stoich value that is then used to calculate the all of the Open Loop injector fuel pulse widths...
Am I on crack? Is the Rob Rauscher (sp) article wrong?
I thought that the millivolt threshold numbers in the Rich, R/L and Lean threshold tables are assigned as the O2 sensor’s inherent “switching stoichiometric” values, which do not change for typical O2 sensors. In closed-loop, the ECU constantly adjusts the injector pulse width to get the O2 sensor output values to be in that “switching stoichiometric” range of O2mV values, say 430 - 460mV. Now the ECU knows you are at stoichimety (you told it to with the mV values) but it does not kow what this AFR value is. So, you also must ASSIGN a CALCULATING stoich value (say, 14.7 in typical cases) to this stoichiometric switching O2value which the ECU ONLY USES in Open Loop calcs, like cold start up and PE enrichment.
To expand on possible changes, you could have an O2 sensor with different mV switching values (like a Wide band O2, for instance) and/or you could have a fuel/air mixture that does not have a 14.7:1 AFR value, like diesel fuel, which is about 18 AFR for arguments sake. So, if the WB O2 sensor switching mV values in the diesel application were 700 – 800mV and we know that the diesel fuel wants an 18:1 AFR, you set the R, R/L and L tables to straddle the 700 – 800mV range and set the calc “stoich” to 18 (instead of the 14.7 for regular fuel).
To wit, if running regular fuel/regular O2, if you tell the ECU that STOICH is 13 and do not change the mV threshold values or any of the OL AFR values, the result will be that the OL actual AFR seen by the engine will be leaner but closed-loop operation would not change whatsoever. If STOICH is labeled as 13.0 and PE enrichment is 13 at all points, the open loop calcs will result in a "truly" stoichiometric AFR at the spark plug as they happen to match in this case.
ie, the ECU doesn't toggle around "14.7" while in closed loop, it toggles the BPW to get the O2 readings around the R, R/L, L threshold mV values that you supply.
In other words, the 14.7 stoich value is NEVER NEVER used in closed loop operation, whatsoever, but is the assigned stoich value that is then used to calculate the all of the Open Loop injector fuel pulse widths...
Am I on crack? Is the Rob Rauscher (sp) article wrong?
08-23-2002, 06:32 PM
#7
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Originally posted by fast_broker
So, Grumpy, raising the values WILL truly slightly richen up the mixture while in closed loop. Also, the calculated AFRs while in Open Loop will be slightly effected as well, and be slightly richer? I am under the belief that the ECU hunts to make the O2 sensor swing about that switch point (R, R/L, L thresholds) and you TELL the ECU that this point is 14.7 so it can make its OPEN loop calcs.
Another question on Proportional Duration Term vs O2 error:
Seconds, ASDZ 7747 PROM
0.03 little error
0.05
0.08
0.08
0.10
0.13
0.20 mod error
0.30
0.60
1.20
2.40
6.00
6.00 lots of error
Q) Are the BPW changes (from the prop Gain calculations) used for the ENTIRE prop Duration Terms above, or is the duration "stopped" when, say, the rich/lean flag is changed? ie: How can any prop change last for 6 seconds on a large O2 error????? That's a million years to an engine???
So, Grumpy, raising the values WILL truly slightly richen up the mixture while in closed loop. Also, the calculated AFRs while in Open Loop will be slightly effected as well, and be slightly richer? I am under the belief that the ECU hunts to make the O2 sensor swing about that switch point (R, R/L, L thresholds) and you TELL the ECU that this point is 14.7 so it can make its OPEN loop calcs.
Another question on Proportional Duration Term vs O2 error:
Seconds, ASDZ 7747 PROM
0.03 little error
0.05
0.08
0.08
0.10
0.13
0.20 mod error
0.30
0.60
1.20
2.40
6.00
6.00 lots of error
Q) Are the BPW changes (from the prop Gain calculations) used for the ENTIRE prop Duration Terms above, or is the duration "stopped" when, say, the rich/lean flag is changed? ie: How can any prop change last for 6 seconds on a large O2 error????? That's a million years to an engine???
confusion. My response pertains to the question of proportional
duration. As Grumpy posted the commanded AFR and R/L O2 windows
are separate items. More on that later. For a primer
see the 747fueling paper on the gmecm site).
Yes, you are reading it correctly. There is also an offset term
added to this that increases the prop duration. Typically
not a large value. The proportional duration term is reset
whenever there is a cross-count ('747 here).
One thing to keep in mind is that this ECM is designed for truck
engines. Low speed, low-po stuff that does not respond (much)
to tuning changes. The ANLU '746 cal (350 cop car TBI) has halved
the prop delays listed above.
Me, shoot doesn't matter. I've set the max gains to 2. One (1)
if the error is small. Even set the gains to zero (0) for a while.
That was interesting. Steady cruise had the INTegrator
slowly increasing till an x-cnt, then slowly decreasing till
an x-cnt. Darn ECM wanted x-cnts no matter what I did (LOL!).
(edit: should not have used the term x-cnt, that is incorrect.
The ECM is actually attempting to keep the O2 sensor value
within the R/L window. Which is nearly impossible. Hence the
changing INT).
Best way to keep it close was to tighten up the O2 R/L, mean
R/L window. Now that gets us to the next installment. Dog-gone
ECM also wants to know in which direction the O2 reading is moving. . .
(One thing to keep in mind is that the TBI has a wet flow
manifold. This is a storage or absorber of fuel, depending
upon the change in manifold pressure. Now don't you guys
w/port gloat too much, your manifolds still do the same).
RBob.
P.S. One (1) prop gain count is 15.26 usec of injector
time. Two (2) prop gain count is 30.52 usec of injector.
Last edited by RBob; 08-24-2002 at 08:41 AM.
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08-24-2002, 02:27 PM
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Originally posted by fast_broker
I guess I'd still like to know why the R, R/L and L threshold table don't hinge around the 450mV switch point of the O2 sensor (the mV values are about 391mV - 422mV, depending on the cal). I assume that there is a reason for this?
I guess I'd still like to know why the R, R/L and L threshold table don't hinge around the 450mV switch point of the O2 sensor (the mV values are about 391mV - 422mV, depending on the cal). I assume that there is a reason for this?
Hard to tell.
RBob.
08-26-2002, 02:29 PM
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Originally posted by fast_broker
now I am totally confused:
I thought that the millivolt threshold numbers in the Rich, R/L and Lean threshold tables are assigned as the O2 sensor’s inherent “switching stoichiometric” values, which do not change for typical O2 sensors. In closed-loop, the ECU constantly adjusts the injector pulse width to get the O2 sensor output values to be in that “switching stoichiometric” range of O2mV values, say 430 - 460mV. Now the ECU knows you are at stoichimety (you told it to with the mV values) but it does not kow what this AFR value is. So, you also must ASSIGN a CALCULATING stoich value (say, 14.7 in typical cases) to this stoichiometric switching O2value which the ECU ONLY USES in Open Loop calcs, like cold start up and PE enrichment.
To expand on possible changes, you could have an O2 sensor with different mV switching values (like a Wide band O2, for instance) and/or you could have a fuel/air mixture that does not have a 14.7:1 AFR value, like diesel fuel, which is about 18 AFR for arguments sake. So, if the WB O2 sensor switching mV values in the diesel application were 700 – 800mV and we know that the diesel fuel wants an 18:1 AFR, you set the R, R/L and L tables to straddle the 700 – 800mV range and set the calc “stoich” to 18 (instead of the 14.7 for regular fuel).
To wit, if running regular fuel/regular O2, if you tell the ECU that STOICH is 13 and do not change the mV threshold values or any of the OL AFR values, the result will be that the OL actual AFR seen by the engine will be leaner but closed-loop operation would not change whatsoever. If STOICH is labeled as 13.0 and PE enrichment is 13 at all points, the open loop calcs will result in a "truly" stoichiometric AFR at the spark plug as they happen to match in this case.
ie, the ECU doesn't toggle around "14.7" while in closed loop, it toggles the BPW to get the O2 readings around the R, R/L, L threshold mV values that you supply.
In other words, the 14.7 stoich value is NEVER NEVER used in closed loop operation, whatsoever, but is the assigned stoich value that is then used to calculate the all of the Open Loop injector fuel pulse widths...
Am I on crack? Is the Rob Rauscher (sp) article wrong?
now I am totally confused:
I thought that the millivolt threshold numbers in the Rich, R/L and Lean threshold tables are assigned as the O2 sensor’s inherent “switching stoichiometric” values, which do not change for typical O2 sensors. In closed-loop, the ECU constantly adjusts the injector pulse width to get the O2 sensor output values to be in that “switching stoichiometric” range of O2mV values, say 430 - 460mV. Now the ECU knows you are at stoichimety (you told it to with the mV values) but it does not kow what this AFR value is. So, you also must ASSIGN a CALCULATING stoich value (say, 14.7 in typical cases) to this stoichiometric switching O2value which the ECU ONLY USES in Open Loop calcs, like cold start up and PE enrichment.
To expand on possible changes, you could have an O2 sensor with different mV switching values (like a Wide band O2, for instance) and/or you could have a fuel/air mixture that does not have a 14.7:1 AFR value, like diesel fuel, which is about 18 AFR for arguments sake. So, if the WB O2 sensor switching mV values in the diesel application were 700 – 800mV and we know that the diesel fuel wants an 18:1 AFR, you set the R, R/L and L tables to straddle the 700 – 800mV range and set the calc “stoich” to 18 (instead of the 14.7 for regular fuel).
To wit, if running regular fuel/regular O2, if you tell the ECU that STOICH is 13 and do not change the mV threshold values or any of the OL AFR values, the result will be that the OL actual AFR seen by the engine will be leaner but closed-loop operation would not change whatsoever. If STOICH is labeled as 13.0 and PE enrichment is 13 at all points, the open loop calcs will result in a "truly" stoichiometric AFR at the spark plug as they happen to match in this case.
ie, the ECU doesn't toggle around "14.7" while in closed loop, it toggles the BPW to get the O2 readings around the R, R/L, L threshold mV values that you supply.
In other words, the 14.7 stoich value is NEVER NEVER used in closed loop operation, whatsoever, but is the assigned stoich value that is then used to calculate the all of the Open Loop injector fuel pulse widths...
Am I on crack? Is the Rob Rauscher (sp) article wrong?
The current commanded AFR is used in the BPW calculation. This is true of both open and closed loop operation. While in open loop the ECM generates ('747 here) the commanded AFR from two tables: AFR vs manifold vacuum and AFR vs coolant temperature. While in closed loop the ECM uses the stoich AFR term.
On a perfectly tuned engine, VE tables and everything else dead on, the ending AFR (in the chamber) will match the commanded AFR. In open loop the commanded AFR changes according to manifold vacuum. The ASDZ cal shows a 3.5:1 AFR change over the range of 0 to 80 KPa. This AFR is also lower with a cooler engine coolant temperature.
With the commanded AFR included in the BPW calculation the injector fueling will create the proper BPW for the commanded AFR. If commanded to be 16:1 it will be 16:1. If commanded to be 13:1, the injector pulse width will increase to provide the additional fuel for 13:1 AFR (our perfect engine again).
As you mentioned, when in closed loop the ECM does follow the R/L O2 terms. This allows the stoich value (14.7) to be calibrated. This calibration is accomplished through the short and long term fuel trims (INT & BLM).
The BPW calculation is using the closed loop stoich term (14.7) while in closed loop. Then with the O2 sensor toggling about stoich, adjusted by the fuel trims, the ECM has calibrated the fuel delivery to the commanded AFR of 14.7:1.
Expounding on two particular statements:
****To expand on possible changes, you could have an O2 sensor with different mV switching values (like a Wide band O2, for instance) and/or you could have a fuel/air mixture that does not have a 14.7:1 AFR value, like diesel fuel, which is about 18 AFR for arguments sake. So, if the WB O2 sensor switching mV values in the diesel application were 700 – 800mV and we know that the diesel fuel wants an 18:1 AFR, you set the R, R/L and L tables to straddle the 700 – 800mV range and set the calc “stoich” to 18 (instead of the 14.7 for regular fuel).****
That is correct. Would also need to adjust the open loop AFR tables to the desired values (based on lambda).
****To wit, if running regular fuel/regular O2, if you tell the ECU that STOICH is 13 and do not change the mV threshold values or any of the OL AFR values, the result will be that the OL actual AFR seen by the engine will be leaner but closed-loop operation would not change whatsoever. If STOICH is labeled as 13.0 and PE enrichment is 13 at all points, the open loop calcs will result in a "truly" stoichiometric AFR at the spark plug as they happen to match in this case.****
In this case the open loop (OL) AFR (in the chamber) would be whatever the commanded OL AFR was. The stoich of 13 AFR would not effect the OL AFR.
UNTIL the closed loop mode is run. The 13 AFR stoich term will then be used in the BPW calc. This in turn will increase the BPW in order to provide the required fuel. Once the O2 sensor reports a rich mixture the ECM will bring the BPW back into line with the R/L O2 thresholds. It will do this by adjusting the short and long term fuel trims. The BLM and INT will drop in value, leaning the mixture.
Now things are not quite right. As the ECM has calibrated stoich to be 13.0:1 AFR. Going back to open loop will cause the commanded OL AFR to be lean in the chamber. This is due to the long term fuel trim still being used while in open loop.
Here is the BPW calculation as used in the '747 ECM:
BPW = BPC * MAP * ~T * ~AFR * VE * BVcor * BLM * DFCO * DE +- CLT
RBob.
08-27-2002, 09:25 AM
#13
Phew. I was pretty close. Thanks for taking the time to answer so thoroughly.
now, if I could only get the slight wander out of my idle, I will be one happy camper.
Oh, I must suggest to everyone to TRY raising the Rich, R/L and Lean threshold mV values to higher numbers, ie to straddle 450mV instead of 391mV, as in ASDZ. Single best change I've made to date with 7747 ECU programming.
now, if I could only get the slight wander out of my idle, I will be one happy camper.
Oh, I must suggest to everyone to TRY raising the Rich, R/L and Lean threshold mV values to higher numbers, ie to straddle 450mV instead of 391mV, as in ASDZ. Single best change I've made to date with 7747 ECU programming.
08-27-2002, 11:16 PM
#14
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Would there be a VE table re-tweak in order. I'm always adjusting something so it wouldn't be a big deal. I almost have it how I want it.
...then again I'm about to put those Vortec heads on soon so there goes the VE table...
Also, what did you like about the change?
...then again I'm about to put those Vortec heads on soon so there goes the VE table...
Also, what did you like about the change?
Last edited by V8Astro Captain; 08-27-2002 at 11:35 PM.
08-28-2002, 08:21 AM
#15
Essentially just slightly lowered the perceived AFR in closed loop. Helped a lot with drivability across the board and with idle quality. I suppose it would effect the VE tables, but it would only be slight and not necessary.
Yep, your heads are going to require a VE tune. Have fun. Did you decide on another cam to go with them?
I still have problems with idle stability (at times!) in CL. 825rpm requested, it periodically goes into the lean/rich hissy fit, while other times smooth as silk. I think my VE table needs some smoothing around idle, and just note that it will be DRASTICALLY changed from a mellow cam. Anyone have any VE smoothing ideas/recommendations at idle for 7747 with vac ref'd FPR and MPFI control? ie, how far apart should the cells be from each other as a general starting point? Like 2 units, or 1? with 4 a max, etc... I think it's a VE table/BLM thing and when I get the time to drive with WINALDL to fix the VE table, I'll be all set but I'd still like some "lessons learned" from you guys.
Thanks in advance.
Yep, your heads are going to require a VE tune. Have fun. Did you decide on another cam to go with them?
I still have problems with idle stability (at times!) in CL. 825rpm requested, it periodically goes into the lean/rich hissy fit, while other times smooth as silk. I think my VE table needs some smoothing around idle, and just note that it will be DRASTICALLY changed from a mellow cam. Anyone have any VE smoothing ideas/recommendations at idle for 7747 with vac ref'd FPR and MPFI control? ie, how far apart should the cells be from each other as a general starting point? Like 2 units, or 1? with 4 a max, etc... I think it's a VE table/BLM thing and when I get the time to drive with WINALDL to fix the VE table, I'll be all set but I'd still like some "lessons learned" from you guys.
Thanks in advance.
08-28-2002, 11:58 AM
#16
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Transmission: sebin hunnerd
Axle/Gears: fo-tins
My idle was always kinda flaky. The rpm would bounce out of no where. Then it would surge a bit then settle down.
Then I tried the open loop idle and now I can't tell it's running when sitting at a stoplight. I know the first reaction is to say it's not tuned right and I need to blah blah blah...but the van did this from day one with the OEM 4.3 and 488 (?) ECM. Althought back then it wasn't as severe.
I did this AFTER I had the BLM at idle at 128.
This is what my VE table looks like at idle. The engine idles at 800 x 30
Then I tried the open loop idle and now I can't tell it's running when sitting at a stoplight. I know the first reaction is to say it's not tuned right and I need to blah blah blah...but the van did this from day one with the OEM 4.3 and 488 (?) ECM. Althought back then it wasn't as severe.
I did this AFTER I had the BLM at idle at 128.
This is what my VE table looks like at idle. The engine idles at 800 x 30
Code:
400 800 1200 40 25 65 85 30 36 64 67 20 5 10 5
08-28-2002, 04:25 PM
#17
I didn't even know you could force Open Loop at idle. How'd you do that on the 7747??? PLEASE, do tell..
I idle at 825rpm with 45MAP. Maybe I should raise my idle speed. The problem is that with the ProJEction ECU as the controller with a large-cap non-conputer controlled distributor, it idled pretty smoothly at stoich at 800rpm all day long, so I KNOW it can be fixed. I did have about 36degrees BTDC of spark at idle with that setup, though, and am only running maybe 27-30 now, can't remember. Could be a small part of it?
Please let me know how to force OL idle. One for the data bank...
Thanks in advance, no pun intended.
I idle at 825rpm with 45MAP. Maybe I should raise my idle speed. The problem is that with the ProJEction ECU as the controller with a large-cap non-conputer controlled distributor, it idled pretty smoothly at stoich at 800rpm all day long, so I KNOW it can be fixed. I did have about 36degrees BTDC of spark at idle with that setup, though, and am only running maybe 27-30 now, can't remember. Could be a small part of it?
Please let me know how to force OL idle. One for the data bank...
Thanks in advance, no pun intended.
08-28-2002, 07:49 PM
#18
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I have my commanded idle set to 650, but the WinALDL BLM table shows the green square in the 800 cell.
This is from my bin. The important part is the RPM qualifiers. You can see that the ARJU code has it turned off by setting the enable RPM really low.
This is directly from the ARJU hack...
From earlier in the thread....I'm keeping my Ram Jet cam when I put the heads on. Money being the issue.
This is from my bin. The important part is the RPM qualifiers. You can see that the ARJU code has it turned off by setting the enable RPM really low.
Code:
LD2A0 FCB 34 ; 850 RPM, OPN LOOP RPM THRESH IDLE OFF LD2A1 FCB 38 ; 950 RPM, OPN LOOP RPM THRESH IDLE ON
Code:
;--------------------------------------------- ; OPEN LOOP IDLE CALIBRATIONS ; L05 ;--------------------------------------------- LD29E FCB 4 ; 4 MPH, OPN LP IDLE THRESH LD29F FCB 5 ; 2%, OPN LP IDLE THRESH TPS ; LD2A0 FCB 1 ; 25 RPM, OPN LOOP RPM THRESH IDLE OFF LD2A1 FCB 2 ; 50 RPM, OPN LOOP RPM THRESH IDLE ON ; LD2A2 FCB 160 ; 8.0 Sec OPN LP IDLE AFR RATIO ENABLE TIME DELAY LD2A3 FCB 100 ; 5 Sec OPN LP IDLE AFR RATIO TIME DELAY LD2A4 FCB 137 ; 13.7 OPEN LOOP AFR MAX AT IDLE
Last edited by V8Astro Captain; 08-28-2002 at 07:52 PM.
08-29-2002, 06:52 AM
#19
Oh, I thought those tables were for IDLE OPEN LOOP RPM SPEED control, not for Idle AFR control. ie, the IAC will stop controlling Idle RPM SPeed in Open Loop Idle Control? Mine are set to the low values as in your bin example. Duh... Guess I should pay more attention to the hack.
So with your values, when Idle gets above 950rpm, it goes into AFR closed-loop mode and when it drops back below 850rpm, it goes into Open Loop AFR mode? Is it that simple to change??? I hope so.
The RamJet cam is good enough but surely needs 1.6 rockers in the Vortec heads...
Thanks again for all the help/replies. Open Loop idle on my horizon???
So with your values, when Idle gets above 950rpm, it goes into AFR closed-loop mode and when it drops back below 850rpm, it goes into Open Loop AFR mode? Is it that simple to change??? I hope so.
The RamJet cam is good enough but surely needs 1.6 rockers in the Vortec heads...
Thanks again for all the help/replies. Open Loop idle on my horizon???
08-29-2002, 09:46 AM
#20
While we’re at it:
What is the Idle and non-idle INT delay:
LD2FA FCB 9 ; 225 msec, INTEGRATOR DELAY BIAS AT IDLE, (sec * 40)
Why is the idle delay small vs the non-idle INT delay at the low Air Flow numbers of idle???:
;----------------------------------------------
; INTEGRATOR DELAY vs AIR FLOW
; 5 LINE TBL, USE AIR FLOW 0-64 BIN
;
; MULT x INT DELAY MULT (Vs. Slo o2) * LD4CC
;
;TBL = Sec's * 40
; = msec * 0.04
;----------------------------------------------
ORG $048F ; msec's AIR FLOW
;----------------------------------
LD48F FCB 23 ; 575 0
LD490 FCB 14 ; 350 16
LD491 FCB 10 ; 259 32
LD492 FCB 7 ; 175 48
LD493 FCB 5 ; 125 64
;----------------------------------------------
ie, shouldn’t the INT delay at idle be more like 500 – 575 msec like the low airflow numbers in the non-idle table???
What is the actual function of this delay, anyway? Delay INT changes for said period of time??? Purpose??? Hmm…
What is the Idle and non-idle INT delay:
LD2FA FCB 9 ; 225 msec, INTEGRATOR DELAY BIAS AT IDLE, (sec * 40)
Why is the idle delay small vs the non-idle INT delay at the low Air Flow numbers of idle???:
;----------------------------------------------
; INTEGRATOR DELAY vs AIR FLOW
; 5 LINE TBL, USE AIR FLOW 0-64 BIN
;
; MULT x INT DELAY MULT (Vs. Slo o2) * LD4CC
;
;TBL = Sec's * 40
; = msec * 0.04
;----------------------------------------------
ORG $048F ; msec's AIR FLOW
;----------------------------------
LD48F FCB 23 ; 575 0
LD490 FCB 14 ; 350 16
LD491 FCB 10 ; 259 32
LD492 FCB 7 ; 175 48
LD493 FCB 5 ; 125 64
;----------------------------------------------
ie, shouldn’t the INT delay at idle be more like 500 – 575 msec like the low airflow numbers in the non-idle table???
What is the actual function of this delay, anyway? Delay INT changes for said period of time??? Purpose??? Hmm…
08-29-2002, 11:52 AM
#21
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Engine: check
Transmission: check
Originally posted by fast_broker
While we’re at it:
What is the Idle and non-idle INT delay:
LD2FA FCB 9 ; 225 msec, INTEGRATOR DELAY BIAS AT IDLE, (sec * 40)
Why is the idle delay small vs the non-idle INT delay at the low Air Flow numbers of idle???:
;----------------------------------------------
; INTEGRATOR DELAY vs AIR FLOW
; 5 LINE TBL, USE AIR FLOW 0-64 BIN
;
; MULT x INT DELAY MULT (Vs. Slo o2) * LD4CC
;
;TBL = Sec's * 40
; = msec * 0.04
;----------------------------------------------
ORG $048F ; msec's AIR FLOW
;----------------------------------
LD48F FCB 23 ; 575 0
LD490 FCB 14 ; 350 16
LD491 FCB 10 ; 259 32
LD492 FCB 7 ; 175 48
LD493 FCB 5 ; 125 64
;----------------------------------------------
ie, shouldn’t the INT delay at idle be more like 500 – 575 msec like the low airflow numbers in the non-idle table???
What is the actual function of this delay, anyway? Delay INT changes for said period of time??? Purpose??? Hmm…
While we’re at it:
What is the Idle and non-idle INT delay:
LD2FA FCB 9 ; 225 msec, INTEGRATOR DELAY BIAS AT IDLE, (sec * 40)
Why is the idle delay small vs the non-idle INT delay at the low Air Flow numbers of idle???:
;----------------------------------------------
; INTEGRATOR DELAY vs AIR FLOW
; 5 LINE TBL, USE AIR FLOW 0-64 BIN
;
; MULT x INT DELAY MULT (Vs. Slo o2) * LD4CC
;
;TBL = Sec's * 40
; = msec * 0.04
;----------------------------------------------
ORG $048F ; msec's AIR FLOW
;----------------------------------
LD48F FCB 23 ; 575 0
LD490 FCB 14 ; 350 16
LD491 FCB 10 ; 259 32
LD492 FCB 7 ; 175 48
LD493 FCB 5 ; 125 64
;----------------------------------------------
ie, shouldn’t the INT delay at idle be more like 500 – 575 msec like the low airflow numbers in the non-idle table???
What is the actual function of this delay, anyway? Delay INT changes for said period of time??? Purpose??? Hmm…
RBob.
08-30-2002, 07:01 AM
#23
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Originally posted by fast_broker
Bias, that makes sense.
So, what does INT delay actually do? What does it get you?
Bias, that makes sense.
So, what does INT delay actually do? What does it get you?
RBob.
08-30-2002, 09:14 AM
#24
So if I INCREASE delays, the INT will be slower to act, which COULD help my idle variations a bit by reducing the speed at which BPW decision changes are made.
This sounds rather similar to the what would happen if I decrease the PROP values at idle... ie, the changes made to BPW at idle would be smaller after I decrease the idle prop gain mult and/or percentage Prop Gain Idle factor.
How about the Open Loop idle AFR question above? Is it that simple to make OL IDLE AFR? ALso, the descriptions of IDLE OIL AFR confuse me? Ie, MAX AFR AT IDLE vs LEAN AFR limit at idle. Max - high number = lean. Aren't they the same?
This sounds rather similar to the what would happen if I decrease the PROP values at idle... ie, the changes made to BPW at idle would be smaller after I decrease the idle prop gain mult and/or percentage Prop Gain Idle factor.
How about the Open Loop idle AFR question above? Is it that simple to make OL IDLE AFR? ALso, the descriptions of IDLE OIL AFR confuse me? Ie, MAX AFR AT IDLE vs LEAN AFR limit at idle. Max - high number = lean. Aren't they the same?
08-30-2002, 11:10 AM
#25
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Originally posted by fast_broker
So if I INCREASE delays, the INT will be slower to act, which COULD help my idle variations a bit by reducing the speed at which BPW decision changes are made.
This sounds rather similar to the what would happen if I decrease the PROP values at idle... ie, the changes made to BPW at idle would be smaller after I decrease the idle prop gain mult and/or percentage Prop Gain Idle factor.
How about the Open Loop idle AFR question above? Is it that simple to make OL IDLE AFR? ALso, the descriptions of IDLE OIL AFR confuse me? Ie, MAX AFR AT IDLE vs LEAN AFR limit at idle. Max - high number = lean. Aren't they the same?
So if I INCREASE delays, the INT will be slower to act, which COULD help my idle variations a bit by reducing the speed at which BPW decision changes are made.
This sounds rather similar to the what would happen if I decrease the PROP values at idle... ie, the changes made to BPW at idle would be smaller after I decrease the idle prop gain mult and/or percentage Prop Gain Idle factor.
How about the Open Loop idle AFR question above? Is it that simple to make OL IDLE AFR? ALso, the descriptions of IDLE OIL AFR confuse me? Ie, MAX AFR AT IDLE vs LEAN AFR limit at idle. Max - high number = lean. Aren't they the same?
Yes to the prop gains. These things (proportional gain) can make for some strange behaviour. Ever seen the INT down by 5 and the prop gains adding 16? (BLM locked at 128). You'd think that area of the VE table was rich. When in fact it is lean.
As for the open loop idle it was used on several (all?) of the BBC cals. Try ANTY & ANTZ for how the cal was setup.
I am not sure of your last question, eprom addresses of the terms help to locate them. As for the:
LD2A4 FCB 137 ; 13.7 OPEN LOOP AFR MAX AT IDLE
(I think this is one you asked about) The OL AFR must be less then or the same as this value before OL idle will be enabled. The OL AFR is calc'd even when in closed loop. A quick look at the code appears like there is a delay before going OL idle then a set time in OL idle. (IE: it switches back and forth). This would be required to keep stoich in calibration. I'd have to bench it before making the previous statement a fact.
RBob.
09-07-2011, 04:02 AM
#27
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Car: 90 Chev Suburban 4x4, 5.3L, th400
Engine: 2002 5.3 Vortec swapped in.
Transmission: Stock th400
Axle/Gears: 10blt front/ 14bltSF rear 3.73 gears.
Re: R/L Threshold voltage
Searching never seases to show me how bad *** you guys are! Im studying like mad to get my idle issue resolved so im adding this one to the list of subscribed threads to go back to! Kinda thikning im going to change my R/L/M threasholds down .05v AND take my commanded afr to about 15:1 and see just what that does and go from there. Thanks!
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