Issue: Balancer read timing versus Tunerpro

[rsicard]

Gentlemen:

One last issue. What is seen on the TunerPro screen and what is read off the balancer with a timing light are different numbers. Is there supposed to be any type of correlation between the two or is the TunerPro derived timing an offset value to be added to the balancer read number? Balancer timing on run-in stand (no load) is varying between 0-10 degrees advanced at or off idle. Just wished had a bench signal simulator and output data capture that would capture all the data side by side to see just what the interrelationships, between inputs and outputs, built into the binary file. Please advise. Thanks.

[fastacton]

The readings should be the same provided the base timing is set properly on the engine and in the tune and there are no other ignition related issues.

[rsicard]

The readings should be the same provided the base timing is set properly on the engine and in the tune and there are no other ignition related issues.

Thanks for the reply. The strobed balancer and TunerPro should read the same number? Hmm. Set the base timing by disconnecting one wire from PCM, adjusting distributor to zero degrees advanced on the balancer with timing light. Reading on TunerPro is different and NOT Zero Degrees advance/retard with one wire STILL disconnected. Don't understand. Must be a specific procedure perhaps to get correlation between the two.

[fastacton]

I don't know if they'll be the same with the bypass disconnected, but when reconnected they should be the same.

[rsicard]

I don't know if they'll be the same with the bypass disconnected, but when reconnected they should be the same.

That is the exact issue. When reconnecting the bypass, there appears to be no relationship between balancer and TunerPro. Thinking maybe TunerPro timing number is a command to advance timing, greater than some value(?), by the amount displayed in TunerPro. Looks like some OFFSET value. Please advise. Thanks.

[jim_in_dorris]

by chance is that difference around 9.8 degrees?

[1project2many]

With bypass disconnected ecm/pcm has no idea what actual timing is. Set distributor to zero, shut off engine, reconnect bypass, restart engine, then compare measured timing to tunerpro display.

[rsicard]

With bypass disconnected ecm/pcm has no idea what actual timing is. Set distributor to zero, shut off engine, reconnect bypass, restart engine, then compare measured timing to tunerpro display.

That is what was done. Yet no correlation of the two.

[rsicard]

by chance is that difference around 9.8 degrees?

Don't think so. Whatever the PCM is commanding as read on the TunerPro screen, is totally independent of the limited 0 to 10 degree change seen on the balancer. Mysterious.

[fastacton]

So, you never get more than a 10 degree change in timing? If that's the case, I'd swap out your ignition module and see if that changes things. I've seen ignition modules cause these kinds of problems.

[1project2many]

Proper timing function is accurately described in a service manual. If the system does not operate as described then it is not working properly.


That is what was done. Yet no correlation of the two.

You can use min/max advance limits to force timing to a fixed value on ecm side. This is nothing more than a test to ensure that ecm commanded value and distributor delivered value are in agreement and eliminate cal tables and code as a potential cause. Also allows evaluation of TP displayed timing as delivered timing value is known and fixed. Not all ECM's apply 5V on bypass line when code 42 EST is active for the current ignition cycle. To ensure proper testing, always shut key off, wait 15 seconds, then restart after reconnecting bypass. Module has ability to apply advance when not in bypass mode. Module typically applies 18 -22 deg advance around 2000-2500 rpm.


What kind of change in advance are you expecting from an unloaded engine on a stand? How much change is TP displaying?

[1BadAction]

Actual vs commanded is always going to be slightly different unless you have taken the time to exactly nail your spark latency table. (It should be very close, though) - Sounds like your problems lie elsewhere, maybe the module.

[rsicard]

So, you never get more than a 10 degree change in timing? If that's the case, I'd swap out your ignition module and see if that changes things. I've seen ignition modules cause these kinds of problems.

Thanks for chiming in. Already been done and NO change. Need more ideas.

[rsicard]

Actual vs commanded is always going to be slightly different unless you have taken the time to exactly nail your spark latency table. (It should be very close, though) - Sounds like your problems lie elsewhere, maybe the module.

Module already replaced. TunerPro says from 14 to 27 degree advance. Balancer says 0-10 degrees varies back and forth. Need more ideas.

[rsicard]

Actual vs commanded is always going to be slightly different unless you have taken the time to exactly nail your spark latency table. (It should be very close, though) - Sounds like your problems lie elsewhere, maybe the module.

Forgot to ask, what or where are spark latency tables? Or is this just the spark tables? Please expand on explanation. Thanks.

[rsicard]

Proper timing function is accurately described in a service manual. If the system does not operate as described then it is not working properly.



You can use min/max advance limits to force timing to a fixed value on ecm side. This is nothing more than a test to ensure that ecm commanded value and distributor delivered value are in agreement and eliminate cal tables and code as a potential cause. Also allows evaluation of TP displayed timing as delivered timing value is known and fixed. Not all ECM's apply 5V on bypass line when code 42 EST is active for the current ignition cycle. To ensure proper testing, always shut key off, wait 15 seconds, then restart after reconnecting bypass. Module has ability to apply advance when not in bypass mode. Module typically applies 18 -22 deg advance around 2000-2500 rpm.


What kind of change in advance are you expecting from an unloaded engine on a stand? How much change is TP displaying?

Thanks much for the suggestions. Setting Min/Max timing in TunerPro to same value is ONE VERY GOOD IDEA to see what happens. Will try that. Also will try 1) discharging ECM, open bypass, reconnect ECM, set base timing to zero. 2) Discharge ECM again, connect bypass, hook up power to ECM and start engine to see if there is a difference. Will do this before setting Min/Max to same value. Two darn good things to try to shed light on the issue.

[delcowizzid]

have you got it idling at the correct rpm yet with some iac steps instead of 0 steps so its not pulling spark to idle slower

[1project2many]

Also will try 1) discharging ECM, open bypass, reconnect ECM, set base timing to zero. 2) Discharge ECM again, connect bypass, hook up power to ECM and start engine to see if there is a difference.

A thorough test but not really necessary. Expected ecm behavior is well established.

[rsicard]

have you got it idling at the correct rpm yet with some iac steps instead of 0 steps so its not pulling spark to idle slower

Darn good question. Will have to check that out and get back with you. Thanks much.

[rsicard]

A thorough test but not really necessary. Expected ecm behavior is well established.

Thanks for chiming in. Not certain of the thinking behind you comments. Still appreciated.

[1project2many]

My thinking is that "discharging ECM" is your own test step, apparently consisting of removing battery power from the ecm in some way. It may feel like a very thorough way to make sure that nothing could possibly interfere with achieving the desired results, but there is no "discharge ecm" step in the proper sequence for checking / setting timing. The set timing procedure will not result in any more accurate setting from this additional work.

[rsicard]

My thinking is that "discharging ECM" is your own test step, apparently consisting of removing battery power from the ecm in some way. It may feel like a very thorough way to make sure that nothing could possibly interfere with achieving the desired results, but there is no "discharge ecm" step in the proper sequence for checking / setting timing. The set timing procedure will not result in any more accurate setting from this additional work.

Thanks for the clarification. For the vintage of the ECM, it is doubtful that there are large capacitors to hold a charge. Still mystified as to the relationship of the ECM commanded ignition timing and that actually read off the balancer. Perhaps the ECM commands timing from an offset. Someone must have tuned the ignition timing on the ECM and come up with some conclusions. Will have to patch in pigtail test points to the 4 pin distributor connector, 2 pin reluctor pickup and injectors to test with Oscope to get a better picture of what is going on. Suggestion or comments please. Thanks much.

[1project2many]

Measuring pulse timing between EST and Reference signals will allow comparison between Tunerpro displayed timing and ecm commanded timing. Is that where you believe the error is?


Still mystified as to the relationship of the ECM commanded ignition timing and that actually read off the balancer.
Post two of this thread:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?4376-Issue-Balancer-read-timing-versus-Tunerpro&p=50006&viewfull=1#post50006

[rsicard]

have you got it idling at the correct rpm yet with some iac steps instead of 0 steps so its not pulling spark to idle slower

Thanks for chiming in. This is one part of the stuff that code in the ECM executes. What other parameter interactions are there that the 16197427 ECM can execute? Sure would be nice to know for present and future reference.

[sturgillbd]

Have you measured the timing on the vehicle you drive that has the same ecm? Make sure your timing light isn't the problem. Use tunerpro, connect to the driveable vehicle and compare readings between timing light and what the datastream shows. That will take another unknown out of the equation.

[rsicard]

Measuring pulse timing between EST and Reference signals will allow comparison between Tunerpro displayed timing and ecm commanded timing. Is that where you believe the error is?


Post two of this thread:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?4376-Issue-Balancer-read-timing-versus-Tunerpro&p=50006&viewfull=1#post50006

Thanks much for the reply. Really struggling with the terminology. Can't wrap my head around what has been said. What is being used as "Reference Signals"? To my mind, what TunerPro is displaying for ignition timing is the processed timing command issued out to the ignition module in the distributor. Don't have a clue as to where the error, if it can be called that, is being inserted. Will have to scope it out to see if there are any conclusions that can be arrived at.

[rsicard]

Have you measured the timing on the vehicle you drive that has the same ecm? Make sure your timing light isn't the problem. Use tunerpro, connect to the driveable vehicle and compare readings between timing light and what the datastream shows. That will take another unknown out of the equation.

Thanks again Brian for chiming in. Darn good idea to compare un-modded vehicle with TunerPro and timing light on balancer with the 350 Vortec on the engine stand to see the differences and what may be concluded from that test. May just patch in test pigtails on un-modded vehicle for testing reluctor wheel, ign module output to ECM, ECM processed timing back to ign module. This should get a better handle on the ign timing difference issue. Really like your ideas as to process of elimination. Good troubleshooting. Too many years away from my electronics technician years. Badly need to get back into it. Thanks.

[1project2many]

Really struggling with the terminology. Can't wrap my head around what has been said. What is being used as "Reference Signals"?

Don't have a clue as to where the error, if it can be called that, is being inserted.


I believe you need to do some 101 level coursework. Do you have a factory service manual?

[rsicard]

I believe you need to do some 101 level coursework. Do you have a factory service manual?

Have access to Alldatadiy. Been in electronics for 40+ years. Have no idea where this is going. Let's cut to the chase and explain what is in the head of the writer. The writer should NEVER assume that the reader knows what is in his head. Different folks use differing terminology. Bad communication. Like two speaking differing languages there will always be confusion. Zero value gained.

[1project2many]

The writer should NEVER assume that the reader knows what is in his head.

I am using nothing more than this thread as my basis for judging what you know about this system.

The terminology that you can't wrap your head around is used in the factory manual. It is the same terminology used by many people who work with these systems, both mechanics and do it yourself-ers. It is the same terminology found in many threads and articles on the internet. The basics of system operation are also in the factory service manual and are described in articles and videos on the internet. Yet you have asked the same question multiple times even when the answers seem to have been provided, and you have not provided answers which would have revealed what you already know about this system. It seems as though you do not have a basic understanding of EST and you may be asking us to provide it. This is why I said I believe you need some foundation work and why I asked if you have a manual.

FYI:

REFerence is the signal to the ecm from the ignition module.
EST is the signal from the ecm to the ignition module.
These signals consist of square waves, pulses, that represent crankshaft position and the beginning of spark.
This information is available between section 6E in the factory manual and the notes for codes 42 and / or 43. It may be harder to locate in Alldata.

The EST signal lags behind the REFerence signal. The time difference between corresponding points on the two signals, accounting for the number of crankshaft degrees between pulses and the ignition module spark latency, represents spark advance. Measuring spark advance using the time differenc will allow you to see if measured timing at the balancer matches measured timing at the distributor. This information is not so easy to glean from the manual. I gave you this information but you did not know the names of the signals or you did not make the connection.

I'm sure we are both busy people. I don't mind helping. It would be good if you have a reference sheet with, or a technician's level understanding of, EST operation and the names of the signals between ecm/pcm and the distributor. It seems like some of what you are asking can be answered by reading the manual or Alldata as a reference. It seems as though knowing some of the terms and names used in regards to this system would allow you to perform searches on the internet to find additional quality information and further your understanding.

[rsicard]

I am using nothing more than this thread as my basis for judging what you know about this system.

The terminology that you can't wrap your head around is used in the factory manual. It is the same terminology used by many people who work with these systems, both mechanics and do it yourself-ers. It is the same terminology found in many threads and articles on the internet. The basics of system operation are also in the factory service manual and are described in articles and videos on the internet. Yet you have asked the same question multiple times even when the answers seem to have been provided, and you have not provided answers which would have revealed what you already know about this system. It seems as though you do not have a basic understanding of EST and you may be asking us to provide it. This is why I said I believe you need some foundation work and why I asked if you have a manual.

FYI:

REFerence is the signal to the ecm from the ignition module.
EST is the signal from the ecm to the ignition module.
These signals consist of square waves, pulses, that represent crankshaft position and the beginning of spark.
This information is available between section 6E in the factory manual and the notes for codes 42 and / or 43. It may be harder to locate in Alldata.

The EST signal lags behind the REFerence signal. The time difference between corresponding points on the two signals, accounting for the number of crankshaft degrees between pulses and the ignition module spark latency, represents spark advance. Measuring spark advance using the time differenc will allow you to see if measured timing at the balancer matches measured timing at the distributor. This information is not so easy to glean from the manual. I gave you this information but you did not know the names of the signals or you did not make the connection.

I'm sure we are both busy people. I don't mind helping. It would be good if you have a reference sheet with, or a technician's level understanding of, EST operation and the names of the signals between ecm/pcm and the distributor. It seems like some of what you are asking can be answered by reading the manual or Alldata as a reference. It seems as though knowing some of the terms and names used in regards to this system would allow you to perform searches on the internet to find additional quality information and further your understanding.

Thanks much for explaining. Did an extensive search of this forum for posts on the subject of ignition. Finally found one post by Dave W. in which he posted a schematic of the distributor ignition module. The terminology used to describe the inputs and outputs of the module are misleading. Yet gained an understanding of what is within the module. The ECM processor and memory must derive RPM based on counts from the pickup of the reluctor wheel in the distributor. Once the RPM is established, the time for one revolution at a particular RPM can be established, then the processor can predict a cylinder firing pulse based on processor and memory table derived timing such that the firing pulse comes in at a smaller revolution time. This process repeats at the main executive loop time in the software governing the processor. Just came up with this as I can presently imagine same. Need to think it through further. Still need to think further about the relationship of ECM timing as seen in TunerPro and that strobed off the degrees graduated balancer. Or hook up a O'scope to these signals and hope to find the relationship of the two. Now have a positive schematic of inputs and outputs of the ignition module. Need to instrument the 350 Vortec on the run-in stand and do the same to the 350 V8 pickup and compare the two. May provide more insight.

Like to know what makes these thing tick.

[damanx]

How did I miss this thread......

I've noticed the same issue when using a timing analyzer and comparing the reading to what tuner pro shows.

For what it's worth, because I am running a C3 ecm, I don't put much faith in the tunerpro timing reading. I do know that the different analyzers I've tried are accurate.

I have 3 different analyzers:



All-Test 3800, digital readout using a magnetic pickup in conjunction with the inductive clamp on the number one plug wire.
Kal-Equip 3821, digital readout using a magnetic pickup in conjunction with the pulse coming from the coil.
Kal-Equip 4020, analog meter using a magnetic pickup in conjunction with the inductive clamp on the number one plug wire.
I also have an Equus 5568 timing light that has the "advance" function on it.


All three work and all three accurately read the mechanical timing properly, but, as I recall, the timing reading in TunerPro was always different, although I don't remember how much.

I finally realized that the readings in TunerPro for timing did not really matter, because what did matter, was knock counts and where it was occurring.

I've questioned the purpose of the spark latency table and the best understanding of it that I've gotten, (may not be entirely correct r complete), is that it's function is to correct to frequency and duration of the reluctor pulse at different RPM's. This table varies in values based on things such as distributor size for example.

If you google "gm spark latency table", you will find some "white papers" that discuss this further.

This is my two cents, YMMV.

Edit to add video: (note that the timing in tunerpro is off by 3 degrees or so, and, I believe that the reason for that is that the analyzer is more "real-time" than what TunerPro is showing due to the 160 baud rate of the ECM I'm using.


https://www.youtube.com/watch?v=WiXHWfiONC8

[rsicard]

How did I miss this thread......

I've noticed the same issue when using a timing analyzer and comparing the reading to what tuner pro shows.

For what it's worth, because I am running a C3 ecm, I don't put much faith in the tunerpro timing reading. I do know that the different analyzers I've tried are accurate.

I have 3 different analyzers:



All-Test 3800, digital readout using a magnetic pickup in conjunction with the inductive clamp on the number one plug wire.
Kal-Equip 3821, digital readout using a magnetic pickup in conjunction with the pulse coming from the coil.
Kal-Equip 4020, analog meter using a magnetic pickup in conjunction with the inductive clamp on the number one plug wire.
I also have an Equus 5568 timing light that has the "advance" function on it.


All three work and all three accurately read the mechanical timing properly, but, as I recall, the timing reading in TunerPro was always different, although I don't remember how much.

I finally realized that the readings in TunerPro for timing did not really matter, because what did matter, was knock counts and where it was occurring.

I've questioned the purpose of the spark latency table and the best understanding of it that I've gotten, (may not be entirely correct r complete), is that it's function is to correct to frequency and duration of the reluctor pulse at different RPM's. This table varies in values based on things such as distributor size for example.

If you google "gm spark latency table", you will find some "white papers" that discuss this further.

This is my two cents, YMMV.

Edit to add video: (note that the timing in tunerpro is off by 3 degrees or so, and, I believe that the reason for that is that the analyzer is more "real-time" than what TunerPro is showing due to the 160 baud rate of the ECM I'm using.


https://www.youtube.com/watch?v=WiXHWfiONC8

Thanks ever so much for chiming in. After proceeding from your hints, found a lot of ign timing latency stuff over at TGO. Built an informative file with that stuff. Expanding knowledge of ign timing.