Does the Ignition Module actually control the timing?

[Turbo Dog]

All over the internet I read things about certain modules retarding the timing different amounts above a certain rpm. So when mine quit last week I started looking for one that would out perform a stock one by not retarding the timing. I made a call to an Accel tech line and they said that the ECM controls the timing point rather than the module. Got any data to prove that the module can retard the timing?

 

[Blackbeard44]

From my experience ign modules can affect timing a couple degrees, I do not think they are designed to but through the manufacturing process something happens and it can change initial timing a lil bit,I always check with a timing gun after changing a module, 1 time the timing had been retarded 2 degrees after changing a module out.

 

[Ricko1966]

Yes they do affect timing but it depends on what module you have. The 4 pins do not alter timing. There are 2 variants of 5 pin both will retard timing there are also 7 pin and 8 pin which control timing. So it comes down to what you have.The 5 pins are not rpm controlled. Most are knock sensor controlled. The 5 pin d1941 module retard 5 crankshaft degrees only when the 5 pin is grounded, cool feature to add to a truck with boost or one that only detonated on 100 degree days pulling a trailer. Throw a switch and bring down the timing

Someday when I'm smarter I'm going to use an 8 pin for my own homebrew standalone ignition.

 

[Turbo Dog]

Mine is a 4 pin for my '87 tbi small block. So I guess there isn't any need for a different module. My stock number is 14096048 and what I read was that it retards the timing by 4 degrees at 3000 rpm and 6 at 5000rpm. My stroker is built like a pulling motor and doesn't get about 4500. So I guess what is referred to as the 369 module (that I can't find) that is supposed to add 2 degrees above 3000 isn't true.

 

[Ricko1966]

I thought all TBI were computer controlled timing.i think someone swapped distributors.

 

[JoeR Jr]

A long time ago a few of my friends and I debated the integrity of the aftermarket ignition control modules for GM and Ford vehicles. We had a Chevy TBI truck handy so we broke out the Sun scope for some testing. The GM 7 pin module had several timing steps in it. With the bypass wire disconnected the timing would advance at a predictable RPM (don't remember the exact info) in several steps. Meaning you see at timing jump at 1800, 2500, 3500 PRPMs, or something a lot like that. The aftermarket one we tested had a single step in it. This wasn't a big deal though. When running in EST Mode the PCM controlled the timing and it made no difference which module was connected. Timing advance was the same either way.
There was a significant difference in coil dwell though. This surprised us. On the GM module, dwell varied from maybe 5-60 degrees. It made tiny steps in the changes throughout the RPM range. This kept the coil properly saturated regardless of RPM. It also made dwell changes in relation to available battery voltage to accomplish the same thing. There was a lot going on in them that was not documented anywhere. It did explain why lots of drivers could feel a difference if you replaced the module with a cheap one. The aftermarket modules we tested made dwell changes in big steps. Maybe every 1500 RPMs, and made no dwell changes in relation to available voltage.
It sold me on using OEM parts whenever I messed with one of those distributors.
Joe

 

[Turbo Dog]

JoeR Jr - Thanks for posting your testing. I put in a Borg Warner module and the truck does seem to run a bit differently. Nothing too noticeable, but since I make my living tuning engines (really big industrial ones) I took notice to it. I don't have scope handy or even a garage to work in right now. When the weather gets better I'll pull out a scope and take a closer look. That won't be for several months here in WY.

Ricko 1966 - When the parts store looks up the ignition module using typical model, year, engine size data it shows a 4 pin module. So I doubt it's been swapped but the truck did have a crate engine in it when I bought it. That engine got taken out by a broken oil pressure line to a mechanical guage, locked up so tight we couldn't get the pistons out so I had to get another block.

Truck is a 1987 V30 cab chassis with a flat bed, vin # 1GBHV34K7HS123929, currently has a small block and I think that is what it came with because it is true bare bones truck.