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!!!

[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.

[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...