Judge Ito

Has anybody succesfully installed MSD's DIS 2, 6A or 6A-L on the trailing coils to a second generation Rx7 using the factory igniter and factory ecu? I have tried and gotten no resutls. The MSD works fine for the leading coil but I can't get them to work with the trailing coils using the factory igniter. What I am getting is spark during crank out of all 4 spark plugs but when the engine kicks over the trailing plugs shut OFF. I was on the phone directly with a tech from MSD and he could not figure it out. WE talked about everything. I falsely triggered the DIS 2 box and the box works fine I check the igniter and that was fine, check coils and that is fine. The problem is the trigger signal coming out of the factory ingniter is not triggering the MSD box when I release the ignition key. The tech at MSD told me they only did a ground test while cranking to the second gen models they tried the box ON and saw spark while they did the ground test. but the problem is after the car is running the trail plugs shut off.

Maxthe7man

I am not sure what series you are running, but I had a similar problem with my n/a rx-7(87 FC), I had no trailing spark while the car was running, the TPS was totally out of range, no matter where it was set, the bracket was slightly bent or the switch itself was mounted slightly off, I filed the holes so I could reposition the whole tps slightly, and it came into range so I could adjust to the exact setting per spec, I noticed my trailing ignition came back, with the TPS working properly, the stock ecu uses the tps to switch to zero split at a given rpm point, but if the TPS is off at low speeds you get no spark from the trailings...Thats all I can add...I have the msd on the leadings as well..Max

Judge Ito

This car is an 87 fc. I adjusted the tps with my led adjuster. Ill re adjust with my multimeter tomorrow. You say after adjusting your tps correctly the trail coils fired fine after the engine was running? did you ever check later on if the trail coils keep firing? like after some hard driving that would cause you to re-adjust the tps.

Judge Ito

I'll add this info. when I disconnected the MSD and installed the trail coil back to the factory wires and igniter the trailing fired normally. Did the vise a versa and no spark after the engine kick over. It sparks while you crank but thats about it.

Maxthe7man

Thats a new one to me..... Yah I rechecked, later and they were firing.. I discovered that little quirk of the stock ecu and the TPS by pure accident.. I would have no trailings, then they would reappear when I tapped the throttle but at zero split(the stock ecu goes zero split at about 15% throttle input)..
Its got to be something with the switchover circuitry, are you running 1 msd for each trailling coil right? I'll bet the msd just doesn't like the ignitor signal..Max

Judge Ito

I'm running the MSD DIS 2 box. It's one box with two channels. I'm thinking it comes down to the trigger signal coming out of the trailing igniter to the msd. There is a trigger signal but the msd will not continue to fire. The leading coil has a different igniter set-up and works fine but the trail has one igniter sending two different trigger signals. Max thanks for your input.

Judge Ito

Max. do you have the MSD's firing your trailings right now? If you do could you check if your getting an elictrical pulse. Just use a timing light to your trailing spark plug wire, if the timing light works let me now.

Maxthe7man

Nope, I only run Msd on leadings ...I also found that some timelights won't pickup the trailing firing, I have an old school inline light will, but my new inductive won't, maybe try pulling a plug wire and see if anything at all is actually firing on the trailings with the MSd..Max

rxAustin

Judge,

The trailing ignitor gets mad if it doesn't see coils.
You can see this if you disconnect the trail coils from the ignitors an connect LED's in their place. The LED's will blink a few times, then stop.

It may be possible to connect some sort of inductor to the ignitor to fix the problem. MSD has some sort of ignition adapter that may do this, but I'm not sure because I don't have one here. You might want to check with MSD, or if you want I can look into it here and get back to you.

-83turbo

edit: MSD part #8910 _might_ work.

Judge Ito

when MSDs are used for trailing the trigger signal works for about 2 seconds then the ecu shuts it off. I agree with you there has to be an adapter to fix this problem. Thanks

Judge Ito

I did my test with grounded spark plugs. i didn't want you to test the same way if you had MSD's in your trailing coils. thats why I said use a timing light. At one point I got careless and got shock to the point that my heart is working a bit better

SnowmanSteiner

Well I'm glad I read this considering I was about to buy some MSD ignition boxes. Good luck figuring this out. I'm surprised MSD hasn't done anything since you talked to them, I would expect them to find a solution or at least something to rectify the situation until they can come up with a solution. Good luck with this problem.

- Steiner

$150FC

wouldn't aftermarket coils alleviate this?

rxAustin

No - the problem (I think) is that the ignitor needs to see the inductive spike when the coil fires. Remove the coil from the ignitor, and there's no spike. In addition to reporting a trail coil failure (check your fault codes), the ignitor will actually stop trying to fire at all, even though the ECU is still signaling it.

My thought is that those 2 wire tach adapters (MSD 8910) connected between the trigger wire and +12V will create the desired effect. I have not tried this - maybe this weekend.

FYI - on my car, the only wires connected to the trailing coil pack are the ones that actually make it fire - the other 2 (tach and "status") are not. The ECU is unaware of whether or not the trailing module is working. I observe what others have seen - the coils will fire a few times and then stop with the MSD, whereas they work fine otherwise without it.

-83turbo

Judge Ito

I will not have time to re-try until next week. If by any chance you try this weekend and get the results we are looking for, I would greatly appreciate it if you post here your resluts.

rxAustin

Okay, here's what works for me: I am using a trailing coil module part # N326 18 100B. This is I believe from an earlier model 2nd gen. The N326 18 100A seems to be similar. I'm not sure what the part # was on the module that I was having problems with previously - I will have to dig it up.
What year car, and what part # are you using? It may be specific to certain years.

-83turbo

rxAustin

Okay, so I spoke too soon with the last post. Nontheless, I was able to get MSD's working on the trailing. I connected a noise suppression choke across the white trigger wire and +12 volts - this creates the negative inductive spike that the ignition mogule needs to see in order to report a successful firing to the ECU. I would suggest using a real tach adapter - the two wire one that MSD makes (8910 should do it. I see there is also a 8912 that might be a dual version, but don't have info in this one). With the choke, I saw alot of nasty stuff on the trigger waveform (I only used the choke because I don't have the correct adapter).
Interestingly, I only needed to do this to one channel in order to make them both work, so you may be able to do the same.
The reason this works is that when an inductive ignition fires, it creates a negative voltage spike on the coil primary. This is needed by some tachometers, etc, and also by the Mazda trailing ignitor module. When it sees the signal, it reports to the ECU that all is well. If the ECU doesn't get this signal, it for some reason decides to stop trying to fire the coils. The tach adapter will restore this signal.
Earlier I thought I had it working without any tricks because I had the rotor #1 trail coil connected to an MSD, and the plug was firing away on the strut tower as the engine idled. Turns out there were some wires crossed elsewhere in the system. Anyway, I have now seen both plugs firing consistently, sitting on the strut tower as the engine idles (yes - there were other plugs in the engine at the time).

-83turbo (for some reason, this site still doesn't know who I am...)

Judge Ito

So the MSD tach adapter(8910) gives the ECU the negative voltage spike on the coils primary that it needs for the ECU to send the trigger signal. I will try this first thing Monday morning and report back here. I want to thank you very much for taking your time and helping me figure out this problem. This is what a rotary engine community is all about. If in the future you need my help in anyway don't feel hesitant to ask.

rxAustin

Let us know either way. I am 95% sure this will solve your problem. If not, we're not out of options yet.

813KR$

I know nothing about 2nd gens, but do know when converting over to direct fire ignition with a msd 6a. Paul Yaws directions said to bypass the igniters, because the igniters send out a dirty signal.

rxAustin

2nd gen's are distributorless. The factory ignitors need to be retained because the signals directly from the ECU won't drive an MSD. Also the trailing signals need to be demultiplexed.

Actually I'm not sure exactly what Paul means when he says the signals are 'dirty'. Automotive electrical systems are inherently noisy, so I would expect the ignitor output to have some low level noise to it, but it shouldn't bother the "white wire" trigger on an MSD - this wire pulls about a third of an amp.
Of course on a 1st gen, eliminating the ignitors removes a possible failure point (and they do die every now and then).

rxAustin

Here's the instruction sheet for the MSD-8912 - looks
useful for this application:
http://www.msdignition.com/pdf/8912_dis_adapter.pdf

Judge Ito

Ok I installed the (8910) tach adapter and I get spark after the engine kicks over. The ecu is getting the signal it needs but what is happening now is the rpm arm is lazy to rev and in-accurate and trailing 1 and trailing 2 coils are shooting electricity right through the center of the coil and grounding "visual" high voltage to the driver side strut tower. I keep thanking you for your help austin..

rxAustin

Okay - disconnect the 4 pin connector from the trailing coil pack. Look into the connector going to the coil pack. With the retaining latch at the top, the tach signal coming from the ignitor is the bottom right pin. This is a black wire on mine. Now look into the mating connector on the wiring harness. The pin going to the tach will be the bottom left. Connect this pin to the tach output on your leading MSD and see if the tach works (with the 4 pin connector still diconnected from the trailing coil pack).

As for the arc-over problem - is the spark coming from the actual body of the coil, or is it jumping from underneath the wire boot? If it's coming from the boot, you may be able to fix it with dielectric grease. If it's coming from the body of the coil, it sounds like the coil is bad. What are the spark plug ends of the trailing plug wires connected to when you see this problem? If the spark has too great a distance to jump, you may see this problem.

Actually I'm not RxAustin - for some reason this site thinks I am. But other than that I am unable to log in at at all.

Judge Ito

The visual high voltage is coming directly from the two bodys of the trailing coils grounding to the strut tower. I'm sure is the secondary voltage charge coming straight out of the coil body. I'm going to try the msd 8912 since its for the DIS msd set-up.i'll come back and reply. I haven't figured out who you are. If it matters to you let me know who you are. I will like to know who has taking the time to give me a hand. thanks again.