In my quest of all rotary knowledge, my search has now led me to the late trailing/3rd spark plug. I've looked around here and only found discussions basically stating that it was done, but nothing that talked about the how, only the why and what its benefit was.

Needless to say, at least per Mazda's info anyway, it will improve torque and fuel consumption, though only in the single percentage arena. I'm not going to be asking whether it's worth it or not, rather, HOW it can be implemented. So, to those who would knock the idea of doing it, pelase keep it to yourself.

So, I'm trying to find information on specific placement. I suppose you can somewhat generalize it based on the drawings I've seen with the R26B. How exact one needs to be is kind of the information I'm looking for. One obvious question is do these housings exist in a form that can be purchased? If so, what is their rough cost?

The bigger set of questions though are how is it implemented and how are they timed? I would imagine that due to their placement it would only be a few degrees, but I haven't found any information specific to that end. If it's possible to fire at the same time as the trailing, then it's really not that much of a concern as implementation is easy. If it is a few degrees after the trailing fires, then the question is how to time and trigger such a setup.

That said, I'd love to hear input from those who have already researched this and see what they've discovered.

The reason for this is I'm starting my own 4-rotor project, but I'm looking at options before I get into the nitty gritty. I'm thinking along very similar lines to said R26B save for the variable intake tubes since the room to install something like that isn't very large. The implementation seems pretty simple though. Porting is up in the air until I firmly decide on whether it will remain N/A or I just kick it up a notch and do some sort of FI. I'll be weighing turbocharging vs supercharging as well, but that's neither here nor their at this point. If that were the case, it probably wouldn't be much more than 10 PSI anyway so...

But I don't want to derail my own thread so we'll save that topic for another discussion.

 

well if you've read the SAE papre you know as much about it as everyone else...

actually DOING it on a set of housings is possible, but it goes thru the dowel pin so you have to do something about that oil galley.

finding an ecu that it capable of actually timing the spark is another biggie...

this has all been tried, several shops in japan sold housings for a while, although it didn't really seem to go anywhere

so time to really examine the goals, it you're building a 650hp engine, is 680hp going to make a difference?

 

There's kinda a hole there already and it doesn't go through the dowel pin. It goes through a tension bolt. I have no idea if this is the proper location Mazda used but it sure looks convenient.

 

That hole is for the knock sensor. Imagine the far trailing plug spaced high up equally as far away as the leading and you'll get an idea of where it was. It will be right in the dowel pin.