FD Direct ignition Coil in FB.... it works!
 

Today I hooked up a spare 3rd gen leading coil that I had sitting around to my '83 SP 12a. I started by unpluging the stock leading coil and ran the + and - wires over to the FD coil. Then I disconnected the leading spark plug wires from the distributor and connected them to the new coil. I finished by swaping the trailing wires over to the leading side of the distributor and viola! I'm done. It seems smoother than before, idle, crusing, WOT, decel....pretty much everywhere. It was'nt a huge power increase or anything, but it does feel better. I'll post some pics in a bit.

I have heard that this has works for some folks BUT I did the exact thing a few months ago and blew up my leading ignitor. So beware. I think there's an impedence difference between the two style coils and it overheated my ignitor. If I were you I would make sure you have a spare ignitor handy and reinstall your J-109 ignitor with a good smathering of heat-sink compound so it has good heat transfer. Let us know how it works out over time.

i would do that right now if I wasnt doing a TII swap,

sounds like a great simple swap with good improvements

The spare ignitor is already in the ashtray, and the stub screw driver is in the storage bin ;)

How long did it last until yours blew up?


here are some pics:
https://www.rx7club.com/forum/attach...postid=1290666
https://www.rx7club.com/forum/attach...postid=1290670

About 200 miles.

BTW, to set the record straight, I used a 2nd Gen coil instead of a 3rd Gen. Not sure what the real diff is though.

I also did not re-seat my ignitor with new heat-sink compound when I did it. I'm willing to try it again with the heat-sink compound but I hafta get a spare ignitor first.

cool thanks. I'll report back after the next oil change or something (1000 miles away)

Okay... I took off the leading ignitor and smuthered the back of it with heat sink compound. I'm happy to say everthing seems to be working well so far.

btw, the leading ignitor is the one closer to the front of the car, correct?

correct

Also, the reason for permature failure of the ignitor is that your now asking it to do twice the work. It now has to fire 2 coils insted of one. Instead of carrying a spare ignitor, just parallel wire them to the mag trigger and have them go to the L coils seperately. This is a tried and true method.

Update
 

Well, it's been well over 1000 miles since I put in the 3rd gen coil. I'm happy to report that it's still performing great.

Thanks for the update! That's excellent news! Mine failed using the 2nd Gen coil, do you know if there's a significant difference between the 2nd and 3rd gen coils?

I have no idea

I have had my FC Trailing coils on for abotu 2 yrs now...Never had a problem.Same ignitors.

Update. I finally blew out the leading ignitor on my 3rd gen coil setup. It was on the last practice session of the day at streets of willow springs raceway. I guess a whole day of racing was too much for the ignitor to handle. I popped another ignitor in and its been fine for a couple weeks now.

Wonder how the GM HEI ignitors handle the FC and FD coils.

So the ignitor finally blew eh? Just out of curiosity, was the ignitor installed using fresh heat sink compound?

thats the reason we do DLIDFIS, use one ignitor to fire one coil... otherwise the ignitor has to deal with twice the current, and as such, a substantialy higher heat load. It might work for a while, but you're over working that poor j-109 terribly.

Yeah it was smothered with heat sink compound, but desert heat and all day racing can kill just about anything, ya know?

It does'nt matter, I'm going Microtech FI soon anyways.