I have seen a few references to firing both plugs in each rotor simultaneously. This would be similar to the way some race piston engines are done with dual plugs per chamber. Anybody done this on a rotary? The dual plugs on a piston engine seem to result in a faster rise in cylindar pressure which may be good for 3% hp. Any pro's and con's to simultaneous firing on a rotary? If it would work well it would simplify going to DFIS on both L & T plugs. 1979 SA 12A.
Any comments and discussion appreciated.

 

You're basically talking about "zero split".
There's a lot of good info on trailing split ignition all over in here.
For the most part on a boosted motor, you need a little split at WOT - that's the prevailing notion.


-Ted

 

Mazda set up the L & T with a split. Most info seems to say the T is mainly to clean up emmissions. I am trying to understand the reasons behind this. If the full DFIS system I am building works as hoped there may be less benefit to the split. Some wankels were set up with only one plug. Maybe with two flame fronts from long duration coil discharge (Kettering) type ignition no splt would be required? If so ,a simpler type of trigger setup could work. Initial and max timing may need to be backed off if the simultaneous firing works out. Is there a Mazda engineer montoring this list who could shed some light on this?

 

Back in the day before the Internet and second generation ignition parts we used to use a MSD 6A to fire the leading and trailing at the same time. These were NA Street ports and Bridge ports for rallying. Never saw a problem. BTW, this was before there were rolling dynos in every city as well. May not have been the most power available but it worked.

Also, I do know that Mandeville (Who has built rotary race engines for 30+ years) uses the least amount a Leading and Trailing split his stand alone EMS will allow. Just enough to make sure the trailing fires after the leading.

-billy

 

Yes! Zero split.
If it works a pair of GM style dual high voltage outlet coils could be used. One to fire both L & T plugs on rotor #1 and annother to fire both plugs on rotor #2. The coils could then be fired by the existing pickups and ignitors. All that would be needed would be a two lobe reluctor with the pickups set to 90 degrees apart. This may be a simpler way to get full DFIS with les than foot long plug wires and only two coils rather than the three needed to do "wasted spark" on Leading and coil per rotor on Trailing.

 

Mazda factory racing recommended zero timing split on their peripheral port housing race engines, but those housings had the trailing plug located closer to the leading plug than stock housings, so those housings liked the zero timing split. I race a peripheral port engine, not with MFR PP housings but with PP housings made from stock housings (RB style,) and I fire the trailing about 4 to 6 degrees after the leading.

 

you need really strong coils to do that. it takes too much engergy to fire BOTH plugs. on a typical waste spark setup one is fired into the exhaust, so it takes almost no energy to fire.

 

some of the big boys running 30+psi...swear by ZERO split

 

hmmmmmm, has there been the thought of maybe drilling a 3rd spark plug hole closer to the leading plug and running those 2 plugs per rotor w/ zero split? either keeping the trailing or not hooking it up...... I havn't looked closely at my housings yet, but would there be an interferance with a coolant path by drilling another plug hole?