I posted a couple of months ago about weird AFR readings, command 14.6 instead of the 14.7 it should be readying and When I first got the car running again after the past winter I noticed that about 10d of timing was being added to cruise for some reason? I disabled all of my egr tables and enable switches which seemed to fix that problem but I've noticed several inconsistant Spark Advance issues just lately.

I have the 30-40kpa columns set to 40d of timing, thats 40d in the table itself. Now on the scan tool it says its running about 40d total, I was under the impression that on the 730 it was base+table spark = total spark?

Another thing is... on my WOT spark it says I'm running about 31d, on my table its set to 28d, on the scan tool it says I'm running 22-24d of timing+the 6 for about 29-31d of timing?

Am I missing something hear? Or is my prom burning not burning to the flash prom properly? I'm going to grab a friends stock 92z28 memcal and chip to put in my car to see what the scan tool reads. I'm really confused at this point.

Brendan

 

A), some scanner round the numbers off, for .1 don't worry.
B) depends on what editor your using. You need to see if the base is included, and it's easy to miss other corrections, you need to read a hac and see what all else there is.
C) don't think so

 

This isnt limited to the 730, the 165 does it too. I was trying to figure out what part of the spark table(s) I needed to modify at different areas and loads by using the numbers my scanner was reporting, and I came to find the same thing you did. Nobody had an answer to it either so I'm glad you joined the club.

I'd bet the base timing is included in the advance numbers. It is on a 165, 6E.

 

Thanks for the reply Grumpy. I went through the first few pages of the Hac for the 730/727, I'm still looking through it but the first thing that caught my eye was the,

;----------------------------------------
; Spark latency correction, (USEC)
;
; TBL = VAL/15.26
;----------------------------------------
; Usec RPM
;----------------------------
L8129: FCB 8 ; 122 800
FCB 11 ; 168 1200
FCB 12 ; 147 1600
FCB 13 ; 183 2000
FCB 17 ; 259 2400
FCB 15 ; 229 2800
FCB 13 ; 198 3200
FCB 13 ; 198 3600
FCB 13 ; 198 4000
FCB 14 ; 214 4400
FCB 14 ; 214 4800
FCB 14 ; 214 5200
FCB 14 ; 214 5600
FCB 14 ; 214 6000
;------------------------------------------


Could somebody explain what this does? It appears to alter the spark values in the tables at specific RPMs?

 

Look here, may help:
http://www.turbobuick.com/forums/sho...referrerid=746

 

Those are the offsets in TIME for the reluctor, and pick-up vs, and the values from the power transistor to turn on and off.
If you look at the GMECM sites, and search for Wors Spoonemore, I beleive he explained it in detail.

And remember those are USEC, not MSEC, so a value of 1 is,

.000001

The referral to the Turbobuick thread switches you from a reluctor A/C generator system like the 3rd Gens use to the Hall Effect of the Buicks, close but not the same.

 

So the spark latency is more or less the reference angle but instead of degrees it's in usec per rpm? Is that about right because I've searched the damn ANHT hac for a spark reference angle to no avail.

 

Ahh ok great, That explains that , thanks Madmax/Grumpy.