I accidentally posted this in the TPI section... relocating it to here.
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Haven't had a chance to really work on the car yet....

But I just started thinking about something (a long shot to be sure): Electromagnetic Interference


I found that I had to shield my Romulator-to-ECM interface cable to make it work. I also get some "popping" noises coming through my speakers (even with the radio off) that sound almost like the ignition coil firing off. The question is has anyone experienced anything like this? I've replaced the little capacitor in the distributor a couple of times already and I plan to put some dielectric grease on the distributor cap terminals. If these things don't cure the EMI, then what else could I attack? The EMI is obviously a problem for other things (even if it's not affecting the ECM), so I want to cure it anyway

 

Solid core spark plugs wires or very low resistance wires will cause your issues. They're non-EFI friendly. What wires are you using?
An the same note, check all of your grounds. I've never had to shield my romulator and I've had TONs of wires laying over the romulator ribben cable which was tapped to the ecm case. Things like 50' worth of dc, high dc high amp (laptop converter), dc to ac converter (for laptop charger), USB to serial, Autoprom burner hooked up and scanning all coiled into this huge mess. No problems with EMI.

 

I'm running Delco plug wires. Matter of fact, they're the exact wires that the L98 TPI Vettes run. I ohmed them out today too. They ranged from 7 kOhm on the shortest wire to 12 kOhm on the longest. Seems pretty good to me.

I also ran another test: Took an AM radio with a set of headphones, set it to a blank station (made sure there was no static with it away from the car on that station) , and started to wave it around the engine bay. IT was really noisy around the alternator, distributor, the wires, the plugs. I could hear the popping from the ignition along with a lot of other static. THen I put it inside the car and waved around the ECM area. Wasn't as bad, but I could definitely hear static and popping. Wonder if the ECM is picking any of this stuff up....

 

The older wiring probably isnt as good at controlling noise as what was used in later efi cars. One cure is to make sure you have lots of good ground points. Engine to battery, chassis to engine, ecm to engine, etc. This will help tie everything together and reduce some of the noise. Also check to make sure that the dist. has good ground path (ie: clean base, clamp, and intake area that the clamp contacts).

FWIW, the radio is the canary of the cars electrical system. You hear something in the radio, you may have a problem. You hear soemthing in the radio with it off, you definatly know you ahve a problem . If your hearing the ignition in the radio, then there is definatly a possible issue somewhere with spark leakage. Everytime I hear the ignition in the radio, I always find some sort of ignition problem. Youll always hear it a little on an AM station, but if it comes through on FM and other sources, then you should investigate.

 

Take all of your plug wires and use zip ties to keep them away from EVERYTHING including valve covers, wire guides, wiring harnesses, steering linkage, you name it. If it's metal, keep it at least 3" away. It sounds like you've got spark not getting to the plug... try the pitch black look for blue sparks test.

 

Yeah, my grounds are excellent. I had a really wierd experience before with bad grounds, having to do with a shifter cable that kept melting it's jacketing! Now however, I have a ground from battery to the engine, engine to the frame, and battery to the frame in two places.

Now, the ignition noise isn't very loud. You have to turn the volume down quite a bit to hear it.

One other indication is this: I tried another experiment today: running the same calibration on a PROM chip and then in my Romulator. The chip worked noticeably better. I'm chalking it up to RFI on the Romulator.

Hmmm... my spark plug wires are kind of bundled together behind the cylinder heads... maybe I'm getting some sort of spark crossing between wires??

 

Hmmm... my spark plug wires are kind of bundled together behind the cylinder heads... maybe I'm getting some sort of spark crossing between wires??

Now, the ignition noise isn't very loud. You have to turn the radio volume down quite a bit to hear it.

One other indication is this: I tried another experiment today: running the same calibration on a PROM chip and then in my Romulator. The chip worked noticeably better. I'm chalking it up to RFI on the Romulator.

 

Been doing some reading on the internet...

Inductive Crossfire=> this might be happening with me. My wires are routed behind the cylinder heads and they're bundled together running parallel to eachother for several inches. I'm going to go separate them out tommorrow and see what happens.

 

It happens often when people try and hide the plug wires. I used to have them out of the way and hidden, even tried running them under the headers. All with great success at first but ending it burned wires and poor engine performance. Ever since burning up 2 sets of MSD spira-core wires I've been running Accel's cheapest 8mm wires and had them all FAR away from anything metalic.

 

I do have some rfi interference when I run with the Romulator in the car.

Going to try shielding it.

Also noticed about the low resistance wires. I found out when I first noticed increased rfi thru the radio.

It picked up alot(rfi more noticeable) since I have been experimenting with enlarging the plug gap slighlty also.

Like was mentioned, I do occasionally experiecne and moreso since increased plug gap of flaky issues using a Romulator vs. the same bin on a chip installed.

Been thru the entire ignition and everything else is satisfactory.

Just have to find mesome nifty shielding. I know people have said tinfoil and the like, would the reflective/metallic style plug wire and wire loom shielding work?

Have some laying around.

later
Jeremy

 

Actually, I posted about that Romulator problem a while ago.

https://www.thirdgen.org/techbb2/sho...mulator+ultm8z


Grumpy suggested some Aluminum foil shielding. What I ended up doing was putting the foil around the ribbon cable as well as securing it with some Aluminum tape. It cured the almost-stalling problem, but like I said a couple of posts above in this thread, there is still apparently an RFI issue with it.

 

Well, I separated the wires out, but it didn't make an difference. I also routed them such that they're not touching any metal. Oh well... it was worth a shot I guess.

 

Also, you have to keep in mind that NONE of the emulators out there are professional grade automotive equipment. Automotive environments are harsh electrically and physically. The emulators really aren't completely designed for either case.
After seeing what is out there. I would expect them to not work most of the time, and work sometime.

The best method for reducing RFI in your case would be to shorten the cable.

Junk