Hi! I stummbled upon a thread here about wasted spark ignition, and it was rather interesing to read. So if I am correct it will help emmisions and a little bit with MPG? As i was reading the rx7 does have it and rx8 doesn`t because of quick wearing of the ignition components in wasted spark setup. But at this time I am making LS ignition adapter harness( I am electrotechnician) and bracket as well so I think the D585 can handle it or isn`t? In the process of making the adapter harness i can introduce a switch to join the trigger signal to the two leading coils for them to fire the two leading spark plugs at once to achieve wasted spark, or better introduce a microcontroller to sense the RPM because in the idle the rx8 is using negative split timing so I dont think here will be the wasted spark inapropriate(wanna introduce the microcontroller under the hood anyway because of turning on/off fans from the onbard pc thru the wifi connection between the pc and microcontroller). BTW I am not concerned about plugs longevity... On the photos you can see my progress with the harness so far, mazda connectors didn`t arrived yet.

 

I would worry about running up against the coils dwell time limits at redline. Since everything is firing twice as often, at 9500rpm you have 6.3ms to cycle a coil without wasted spark, and 3.15ms with wasted spark. I'm not sure it's reasonable to expect that from a typical D585 while maintaining original spark quality.

Look into Mercury IGN1A coils instead. I haven't done the research, but heard they're much better for short dwell applications. Could be I heard wrong.

Also I'm not convinced wasted spark would accomplish anything, since you would be firing the waste spark into the trailing edge of an already fired combustion chamber, which is what the trailing spark plug does anyway (but under compression). Even if you managed to ignite fuel with that, it would provide impulse against the rotor's direction of motion. Maybe I'm misinterpeting the design

 

 

Wasted spark systems are usually used for applications where space and cost are an issue as in motorcycles etc. It is not considered to be better.

 

Totally get it, I'm also a tinkerer. Wasted spark is cheaper to produce and control, maybe it's that. I imagine there's a reason they no longer use it. Also none of them had trailing wasted spark, because that risks igniting the fresh chamber that's undergoing compression, which would be very bad.

 

I know rotaries aren't very efficient at burning gas, but at the same time, I doubt if there is enough unburnt gas and air/oxygen left after a combustion to ignite again. This isn't the RX-3/RX-4 days where they had a thermal reactor in the exhaust.

And I think even Mercury coils have their limit. One thing about them is that they shouldn't be run beyond 40% duty cycle(unless you are racing and you don't mind replacing coils often), and with a waste spark system, I am not sure if you can stay below that.