Oh! I think I see what you mean. You're talking about running leading and trailing with no split.

Waste spark is something different altogether - that involves firing two different cylinders/chambers at the same time - one spark is at TDC compression stroke and the other one is just "wasted".

 

The last time I checked, the Motec does not run the split the same way the OEM computer does it.

 

peejay is right. It is not wastespark (one fires into exhaust cycle), it is parallel firing.

New Haltech does 3 and 4 rotor with full 3D trail control. Seq injection and oil metering pump control too.

Firing the Lead and Trail in parallel does not produce the best power in my experience. A few degrees of split generally have it running better under WOT depending on the motor, fuel and mods. At light throttle it does seem to run fractionally better when fired together, but HC emissions go up considerably. I also the split needs varying more with load than rpm.

 

when does the new haltech come out, is it months or years away? i would like to have the split, but wiring up 2 seperate ems's and programming both was more hassle than its worth at the time i started the project

mike

 

I'm not sure about the Japanese teams, but Downing Atlanta fires them simultaneously through a single M800.

Do you have a link for that? It will only run split timing on a 2-rotor, but will run a 3-rotor with simultaneous timing per race specs.

Roger Mandeville said that the M800 will NOT run the split on a 20B, so I'm going to assume that he knows what he is talking about.

 

the way that the m800 is wired it can't do the split the leading coil pack and trailing coil pack are wired together http://www.motec.com.au/drawings/m16.pdf
you can see the 3 ignition outputs are shared between l and t

mike

 

The new one is weeks away over here for a very small number of units, and only locally near Haltech so each install can be checked on for bugs. I have been playing with one on a 13B for a while and the ECU is getting there very rapidly. Just small stuff to sort.

You guys in the US should see it in couple of months.

 

cool thats fast, i was planning on 20b stage 2 next year (making things look good, polishing, paint etc) maybe i'll redo the ems too.

mike

 

There is no way you can run a wasted spark system on a triple rotor (i.e. fire all three leading or trailing plugs together), because when one rotor fires, one of the other rotors is still in the compression phase (the other is in exhaust). Wasted spark has no effect on either performance or emissions, because the wasted spark is just firing into exhaust gases. It is purely a way to make the ignition system (including the ECU) simpler by reducing the number of coils, ignitors and ECU drivers required.

 

I'm building a 20B ignition and the info here has been very helpful. On my old 2 rotor engine, adding wasted spark has helped power and reduced emissions (old '70s carb), so I was hoping it could be done on a 20B as well. Too bad. Simply prototyping a 20B ignition (without L/T split) has been rather challenging in its own way. Forget the split (for now); I'll be running it like a V6.

 

Assuming you mean "split timing" as opposed to "wasted spark"...

Yes, the split timing was better for the carburated engines, as simultaneous firing could lead to the infamous colliding flame front problem. Modern EFI engines do not have this problem.

 

Uh oh, maybe I'd better have a little split, huh?

 

Us 1st-genners (and pre-RX-7 folk) have been converting to waste spark with two different camps - one mindset uses an additional ignitor and factory coil, another uses a single MSD to drive two MSD coils... either way each leading plug has its own coil and they fire simultaneously.

Anyway, pending the finding of an intact early V6 model, I might have a way of making a CHEAP setup to convert a distributor to fire a 20B in non-split mode... and possibly also with factory-style fixed split if one is willing to make their own distributor cap.

 

Would you mind educating me of this problem?

 

Me too. I'd very much like to go with no split and a carb.

 

Also known as the "cross triggering" problem in older S1 RX-7 breakerless ignitions, it's when the L & T fire at the same time. This can create two flame fronts (one from each plug) which collide and generate perpindicular explosive waves more commonly known as "detonation" or "knock".

I don't know why carb engines are more prone to detonation with simultaneous ignition, while EFI engines run just fine. Maybe one of our technical gurus can explain this?

 

i've been reading my rotary engine book, and of course
this isn't mentioned. they do show that when knock occurs it is right next to the trailing spark plug.

mike

 

Series 1? Well that affects the '80 style only then. Anyway, I've been back to the drawing board and decided to go with an earlier design that has split.

 

The problem with the '80 was due to the fact that both ignitors were encased in one unit. I never had a problem...

 

The problem with the '80 was due to the fact that both ignitors were encased in one unit. I never had a problem...

But I did find out that trailing ignition did NOT want to be more than 10 degrees BTDC under full advance, no matter WHAT. That may have had something to do with it. I seem to recall that later engines have altered spark plug locations.

 

as the rotor moves the trailing side of the combustion chamber is getting smaller and the leading side is getting bigger. this means the flame front moves toward the leading side.

mike

 

And the hard to ignite stuff stays in the trailing side.

 

actually it may have something to do with the shape of the rotor recess. the 13b's have a squarish shape recess, and the 12a's have one that tapered on the trailing side. this taper raises the working gas pressure on the trailing side, that and a misfire could be the culprit, no?

mike

 

This is all very interesting. There were no fuel injected 12As in the US. They'd always need a split. Since the 20B uses 13B sized and shaped rotors, do you think it still requires a split if carbed?

 

The timing requirements don't care if it's EFI or injected.