GM Module timing curves

[chevmasta]

THe DUI Dynamod for the GM distributor is one of the best . I always try to use the 369 module but my NOS stock is fading fast , the new modules you get from GM with the new part might or might not be the genuine 369 like before , there are no markings on the ones I have ordered , just the new part # .

Only way to know for sure is to install it and try it I suppose .

TOM

Maybe we should collectively, on this forum, purchase the new delco module part number and have it tested to see where the values are set in the unmarked delco module?
Just a thought.

I'm getting ready to test my new moates hardware. If it turns out as I hope....I owe Mark $100 anyway. LOL

[chevmasta]

THe DUI Dynamod for the GM distributor is one of the best . I always try to use the 369 module but my NOS stock is fading fast , the new modules you get from GM with the new part might or might not be the genuine 369 like before , there are no markings on the ones I have ordered , just the new part # .

Only way to know for sure is to install it and try it I suppose .

TOM

Because of this thread, I decided to email Performance Distributors and ask them about the "curve" built into their DUI ignition module. This is what they responded with:

Ryan,

The only difference in our module over stock is the increased dwell
time. There is about a 3° retard in the higher rpm's that is inherent to
the module. Thank you.


Performance Distributors (DUI)
2699 Barris Drive
Memphis, TN 38132
www.performancedistributors.com
901-396-5782

[Nasty-Z]

Because of this thread, I decided to email Performance Distributors and ask them about the "curve" built into their DUI ignition module. This is what they responded with:

Well that's weird , contrary to that reply , the one I have in the 434 in my S10 actually acts more like a 369 , IIRC it advanced about 2 degrees or so after 3500 or so RPM.

Dunno.....

TOM

[Fast355]

Well that's weird , contrary to that reply , the one I have in the 434 in my S10 actually acts more like a 369 , IIRC it advanced about 2 degrees or so after 3500 or so RPM.

Dunno.....

TOM

The one in my TPI G20 did the same.

[EagleMark]

Hmmm?

Another test: while checking the timing as the RPM was increased, both the 048 & 369 modules held steady until a particular RPM. This was with 048 & table 1, then 369 with table 2.

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.

The ignition control module stamped "048". This ICM retarded the timing advance beginning at 3,500 RPM premitting the use of 83 octane gasoline and the module acted as a speed governor.

The ignition control module stamped "369" are the ones that was first used on the 1985-1993 Chevrolet Caprice with the 9C1 RPO Police option. This ICM does not retard timing starting at 3500 RPM which provides 4 degrees additional timing by 4,000 RPM with a total of 6 degrees additional advance by 5,000 RPM.

[1BadAction]

This thread scares the shit out of me, because if I'm inadvertently tuning one of the modules that retards then something happens and I end up swapping one on the road somewhere... I could end up with +8 degrees of advance. Right now is a perfect example, I'm about to swap to the 3764 and at the same time I'll be swapping to the MSD billet dizzy with the MSD module. Is the module I have the "good" one that doesn't retard, and the MSD perhaps one that does retard, or the other way around? Guess I'll post on the MSD forums to see what I can dig up.

[1BadAction]

According to MSD tech, there is nothing in their module that adds or removes timing, it is directly controlled by the ECM.

[EagleMark]

Ask them what the Latency settings are from their data sheets? This is a very important setting for GM ICM modules...

[1BadAction]

Ask them what the Latency settings are from their data sheets? This is a very important setting for GM ICM modules...

I just asked... Maybe that'll give the "forum tech" a keyword to ask someone that knows.

[edfiero1]

I know its been over a year since this thread was started, but the thread just stopped without any conculsion.
I'm wondering if you guys have any advice for me. I am using EBL to tune a 4 cylinder engine. I've just discovered that the timing at the distributor does not match what the computer is commanding. (Its off by about 14 degrees at 3000rpm).
Rbob turned me on to the SA - Latency table, but since this is a 4 banger with a completely different ICM (Delco D1964A {#10482833} GM Original Equipment) than what the V6 and V8 cars have, I am guessing that none of the stock BINS that are readily available for the 4.3 or 5.7 are going to match the latency that I need to have.

Is there any short cut to estimating the correct latency values, or do I need to plot out how much difference I am seeing at each RPM and start changing the Latency accordingly? Should I start the plot with the latency values as they are, or should I zero them all out to start?

If the computer is commanding 32 degrees of timing and I am only seeing about 20 with my dial timing light, does that mean I need to increase, or decrease the latency??

[1project2many]

Latency is the "lag time" between the ecm commanding "Spark now!" and the module actually making spark. The ecm compensates for this by sending the "Spark now!" command sooner. If the spark is occurring delayed from the desired timing, and there are no other factors causing it, then the latency time needs to be increased.

Latency can be calculated as the difference in time between commanded spark and actual. We need the commanded advance, measured advance, number of degrees between reference pulses and the RPM at which the error is measured. At 3000 rpm, an error of 14 degrees on a four cylinder engine works out to 780 uS. Note that this is in addition to the latency value already in use. However, before adding anything to the current values I would look at some four cylinder calibration values as a sanity check. 780 uS seems large to me.