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.