Timing issue???

[damanx]

I don't mean to start yet another thread, BUT, this is pretty specific and may be an issue that I need help resolving I believe because I don't think I should be tweaking the timing table before verifying and correcting a problem, IF there is one.

Ok, my base timing was off and was sitting at 4 degrees BTDC when it should have been 0 degrees.

Got that fixed.

Then what concerned me was the difference in reading from the spark advance hack in the $42. I figured out how to add to the adx to show what the actual crank angle is so that it matches the timing light and timing analyzer reading is.

Problem is that the Main Spark table doesn't match up when data tracing.

What am I missing here? Is there a timing problem?

Attached is the bin and idle test that was recorded during the video. Was also using the 5.9.3 xdf.

Here is a video of this:

[EagleMark]

Check your adx file under values, Spark Advance From Hack, then look at bottom for Conversion and if your Base timing at distributor and your initial advance are 0*? Then the conversion should be "(X * 0.3515625) + 0.000000"

If say it was a 7.4L the Initial timing is 3.87 so distributor should be set to 3.87 and the conversion would be "(X * 0.3515625) + 3.870000"

If that is not the cause it is the Spark Latency! None of the stock GM calibrations are exactly correct and they are all different. But that link I gave you before shows how RBob did the math and it can be corrected!

Couple other things to think about are adders and subtracters? Like PE, Coolant comp, Highway spark, Spark Slope, etc...

Interesting note found in that thread that I have verified as well is:

The 048 module, it held steady timing until about 3800 RPM where it retarded 4 degrees. Then by 5000 RPM the retard had increased to 6 degrees.

The 369 module, it held steady timing until about 3200 where it gained 2 degrees of advance. This held steady to 5000 RPM, which is the highest RPM it was checked at.

So there is a difference in modules! This is also a reason I always reomend GM EST/ICM modules because I have checked aftermarket EST/ICM modules and have found some to be off by 12* at higher RPM!!!

[ony]

damanax your timming table needs a repair on it if my xdl is reading it right, eagle mark will proble be on here about 11- 12.

[ony]

man something is wrong with my internet,post one place and its delayed 5 minutes.

[damanx]

man something is wrong with my internet,post one place and its delayed 5 minutes.

A Posting Latency Table issue?

LOL!

[EagleMark]

A Posting Latency Table issue?

LOL!

Can't help with tuning that out...

[damanx]

Check your adx file under values, Spark Advance From Hack, then look at bottom for Conversion and if your Base timing at distributor and your initial advance are 0*? Then the conversion should be "(X * 0.3515625) + 0.000000"

If say it was a 7.4L the Initial timing is 3.87 so distributor should be set to 3.87 and the conversion would be "(X * 0.3515625) + 3.870000"

If that is not the cause it is the Spark Latency! None of the stock GM calibrations are exactly correct and they are all different. But that link I gave you before shows how RBob did the math and it can be corrected!

Couple other things to think about are adders and subtracters? Like PE, Coolant comp, Highway spark, Spark Slope, etc...

Interesting note found in that thread that I have verified as well is:
So there is a difference in modules! This is also a reason I always reomend GM EST/ICM modules because I have checked aftermarket EST/ICM modules and have found some to be off by 12* at higher RPM!!!

Tomorrow, I will pull the distributor rotor and verify the ICM. At this point, I believe I am running the 2.8L distributor, but since I have a spare distributor, I'm not sure because I pulled one off a 3.1 quite a while back.

In any case, I suppose that parts verification would be important prior to messing with advancing spark.

Edit to add:

I notice that in the adx, the Spark Advance conversion is (x*0.3515265)+0.000000 and in the xdf, the conversion is (0.351560 * x) - y.

Why the difference?

[EagleMark]

Why the difference?

Ha! Read other thread.

[damanx]

Well, using the 2.8 distributor and the correct gm ICM for it. It's wired properly also.

Wonder if putting a scope on the ECM would show anything of interest.

It certainly appears that the spark latency table has an effect on that displayed value.

[EagleMark]

It directly does!

Like I said before the EST modules are all the same yet different engines have different latency values. Why? Hell I don't know, but I think GM used it for an adjustment because you can adjust latency and come up exact at timing marks. Then the spark table is truly accurate.

[damanx]

Time to pull out the 4 channel scope and do some looking.

[damanx]

Update:

For the life of me, I am still not seeing a match up on the timing in the data in TunerPro, (spark advance hack), and an actual dial back timing light.

I've learned that there were a few 4.3 bins in the 7747 family that used the same distributors and ignition system as the 2.8's in the 8062 ecms.

This prompted me to try a 4.3 bin today.

Interestingly, the spark advance reading and the timing light still did not match up at higher rpms, BUT, the timing analyzer did match the spark advance reading once I turned one of the switches on the unit to indicate that the harmonic balancer had 4 notches in it. Why, I don't know because the harmonic balancer has 3 notches in it.

In any case, I still don't quite trust the software or the analyzer.

The timing light is the only one I actually trust at the moment, and yes, the formulas for the adx are correct to what the base timing is.

[EagleMark]

I trust the software and a dial back timing light. But even then timing will not match perfectly with stock Spark Latency settings, they are not accurate. They need to be adjusted to match.

Also a lot of variables to looks at, adders/subtractors like "SA - Coolant Comp Spk Adv" etc...

[damanx]

Mark, I think I figured out a few things. (long time coming even for that much....LOL)

The 2.8's shared the same ignition system as a lot of the 4.3's, so it seems that using a 4.3 bin made more sense due to the Spark Latency table being closer between the two versus a bin originally for a v8. The 4.3 bin I am currently using has a MUCH better response and the timing is more advanced like you would expect without the large increase in knocks as seen in the v8 bin. The current spark table isn't as advanced as the 3.4 DIS table, but more advanced than the ASDU bin with the same initial base timing.

So I tried the logging by shutting off the the various parameters, outside the egr stuff, as listed in the XDF for the $42, but that apparently prevents the TCC from locking up via the ECM. Don't know if that is what is wanted or not. Wish there was more clarification on that other than just essentially, "turn it off for more accurate data".

DETAILS MAN!!!! I NEED DETAILS!!!!!!! :)

Also, it seems that changing the parameters to make the ECM run sync mode, does just that, I THINK. In any case, there is a definite improvement in idle quality. In another thread about sync vs. async, the 60v6 is specifically mentioned as not liking the sync bins, and the apparent assumption seemed to be because of the intake runners. I'm not sure I buy that considering the stock TBI intake has the TBI sitting about 30 degrees off center, which I would suspect to place the distance of the injector nozzles more evenly between the 1 and 5, and the 2 and 6 cylinders.

I also learned that the intake for the TBI 2.8's is divided, where one injector feeds 1,3,5 and the other 2,4,6.

This brings up the question of how do I know, or figure out when the injector that feeds 1,3,5 cylinders is supposed to be firing? Timing light or o-scoping that injector with a reference from the #1 spark? (I have an inductive clamp that will trigger a scope.)

Next up is again about the "actual timing" versus what the timing analyzer shows for crank timing.

I think that I am seeing a difference at cruise speeds due to the Spark Knock Retard vs Map. I will have to verify this the next time I drive the truck, but that is what I suspect.

That's about it for the moment.

[EagleMark]

I knew you'd be useful when you came here!

There's nothing in the Turn Off for Data Logging folder that I know of that will turn off TCC? They are all to simple for clarification, it's just turns that EFI feature off. Have you tried turning them back on one by one to see what is effecting TCC lockup? Or could it be your new bin?

You know you can copy the entire spark table from the 4.3L bin to any other $42 mask bin...

Getting timing spot on from spark advance table to timing light at crank takes making your own accurate Spark Latency table. None from GM are accurate and I have no idea why they played with this for timing when they had a timing table?

Coolant spark, EGR spark, Knock retard can all effect final timing...

An O Scope would be the best choice for figuring injector firing. This would be important with a Sync fuel bin.