after reading several write ups on direct fire using the MSD box(the 6), I had come to the conclusion that only the leading plugs are direct fire? Is that true, if so, would one, using 2 msd's would have true direct fire for both the leading and trailing? Any downsides to using 2 msd's for direct fire (expect for the cost)

 

Ywah, you could set the trailing up the same way the leading and do it all direct fire. But you'd have 4 coils, two MSDs, and lots of wiring.

There wouldn't be much gain (if any) from doing it. I'd save the money and leave the trailing alone.

 

not that simple.. you would then have the trailing plugs fireing at the same time, which you donot want.

 

I personally wouldn't worry about trying to make the Trailing direct fire.

A few months ago there was a sort of race to see who could make Trailing direct fire a reality on a 1st gen, or in RX-Midget's case, a rotary powered MG Midget. I think RX-Midget won. He modded a 2nd gen CAS, if my memory serves. I modded a 1st gen distributor and got Trailing direct fire for a 20B (with 0/180º sparks on Leading, woohoo!) around the same time. As I was testing it on my 13B, it was using only one pickup to run both Leading plugs and the other two (Leading) pickups were being set (timed) individually with my marked timing pulley. My 13B was not running on Trailing ignition during this testing and only had a slightly unsmooth idle compared to my regular distributor. Driving on the modded dizzy (still with my 13B) almost felt like the engine had more power. Can this be true? Then when I was driving my rotary powered MG Midget, I accidentally left the Trailing disconnected the first time I drove it (being the first time driving it, I had more things to worry about beside my tach not working). I got out, put the wire on the Trailing coil, and continued driving. The same phenomenon that happened with my 13B testing also happened with my MG on two different distributors. Could my Trailing ignition actually be hurting my power? Is it just a quirck with the engine? One dizzy came out of a GSL-SE, so its advance curve supposedly matches what a 13B wants. The other dizzy is from a 12A, and was running on a 13B.

Well, to answer that question, I've since hooked up a relay for all my ignition parts to get full battery voltage without having to get it through the ancient ignition wires. I have a switch left over from a previous project mounted in easy reach that I'm going to hook up to my Trailing ignition only. The Leading will still be on the relay. This will allow me to open and close the Trailing igniton system on the fly. I'll be able to feel with my butt-dyno if Trailing adds or removes power under different driving conditions. I already know that no Trailing igniton causes a slight unsmoothness at idle, which on my engine, can run down to something like 400RPM while letting the clutch out and not even cause a missfire (it's actually gone down below that to where I no longer hear the engine running, and the tach reads zero, but the stock heavy flywheel keeps things spinning long enough to fire it back up).

You know, the '80 1st gen had partially fired Trailing as stock, so if it's only for emissions (the thermal reactor), I'd think DLIDFIS would give the engine all the extra spark it needs while keeping emissions to similar levels. By the way, the MSD on Leading is sort of the same way. I guess it wouldn't hurt to try?

Sorry this post was so long and probably didn't answer your questions very well.

With an MSD firing both Leading plugs, yes they're direct fire. You can't get Trailing direct fire from a second MSD, unless both were used for Trailing only, and then there's the question of when to fire each MSD etc. You'd need three MSDs, and the Leading MSD would have split voltage going to both Leading coils, unless you had a total of four MSDs - one for each plug. Not worth it, in my opinion.

 

That was long and Im lazy so I didnt read it, but from what I understad, you would need to use at least three boxes to get true direct fire. Even then, you still would need to trigger the trailing boxes seperatly which would just be interesting.

~T.J.

 

Only do this if you want to blow up your engine.

 

Yeah don't do this with the trailing. it will ignite the fuel from the next stroke.

 

You'd need to run three boxes and trigger off the distributer for the two trailing boxes. I understand signaling is way is fairly dirty.