Mystery Ignition Control Module latency and dwell characteristics??

Attachment 15718

This module came in a RamJet 350/502 distributor I installed in my TBI build:

Part # 1104060:
"Used on the fuel injected Ram Jet 350 and Ram Jet 502. Includes ignition module P/N 10482830, cap P/N 19166099 and rotor P/N 10477219." The module I pulled out of it looks like this and I can't confirm exactly what number part it is. I tried to find references to 28184533 but came up dry other than vague references to GM Marine Performance. It's definitely an 8 pin module so it's designed to be controlled by an ECM, which the RamJet engines come with.

Problem is that I get zero spark advance at idle, not sure how far up the RPMs lack of advance goes because I haven't tried it yet. Distributor base timing is set at 18* an confirmed with an Innova 3568 dial-back light. Commanded Idle SA in the tune is 28*. EBL WU Display shows 28* with the same +/- 2-3* fluctuations I see at the damper which only shows 18*.

The SA latency table in the tune has zero values from 400-799RPM, 800-1199RPM. It seems the key, according to discussions here and on TGO and a couple other places over the years stress the importance of these values to producing the desired advance accurately. If this thing has a weird latency curve and dwell time I'd need to find out and enter properly in the table. Otherwise, go with one that's pretty well known like the D1943A, D1965A or maybe even D1984A. A shame to toss a high dollar, perfectly good (albeit useless) ignition part into a drawer.

All the wiring is good from the ICM connector to the EBL ECM (B3, B5, D4, D5). The module tested as good at the local Advance Auto (as I suspected it would).

Anybody seen this module before and know anything about it??

Attachment 15719

Current SA Latency table. Same as the 5.7L TBI base BIN for EBL Flash II. I'd expect this to be appropriate for the D1943A but I'd need to go back through my reading to confirm that.

For testing purposes and to have a spare, I grabbed the dirt cheapest ICM I could find locally. Advance Auto's Driveworks house label. I just wanted to see ~anything~ different from the mystery module. To my shock and surprise the darned thing says made in USA on the box, part # 21026. Certainly could be that the electronic components are made in China and just assembled here, idk.

With this cheapo module the timing advances and retards electronically pretty close to what's commanded. May be 1-2* off at most in the lower RPM range I observed directly. I don't know and probably wouldn't be able to get an answer from Advance/ Carquest as to the module's latency specs but I might float an email out there to them and see, just in case. I'm going to get a D1943A in the next few days and make some minor changes to the SA - Latency table based on my reading at TGO of a discussion around some good testing.

I'm wondering if the mystery module is a marine module that has its own timing curve built into it and I just didn't rev it far enough to see it advance since my focus was on idle at 775RPM... I really would like to know something (anything) about it.

From a RamJet 502

Quote:

---

Originally Posted by In-Tech

From a RamJet 502

---

Amazing, thank you! That is a very interesting latency curve and very different from either the 048 or 369 modules...

Attachment 15725

I did fudge and add the last data point for the RJ502 module at 6,000RPM. I want to test using these numbers as soon as I get a chance and report back just to get it on record somewhere if this matches the hardware. I may simply fill in median values at the 400RPM gaps, though there could be similar non-linear swings like in the 048 and 369 modules. But this just seems like a different animal altogether.

Thanks again.

An interesting tidbit of info. Most of the GMPP calibration files have incredible amounts of errors in them, including the newer E67 stuff. Their calibration department just seems to do enough to barely get by. Here is the spark delivery lag from a real Merc Marine 502 file.