In all out race cars it is typical to run zero split between leading and trailing. The split was a trick to get better HC numbers at idle and low RPM. In stock classes they do see a small HP improvement but HC at low RPM is not a factor a 5,500 to 6,000 RPM cruise. Plus firing both at once makes ignition systems a bit more simple, and if you hook the wires up backwards on one housing it has no effect at all. Center electrode wear is affected if you use just one double ended coil for one housing. So, you reverse the wires half way through the plug life to even things out. One plug is always firing backwards you see. The leading plugs can both fire at once in the lost spark situation (stock setup on many models of Mazda).  The trailing plugs must be distributed because an apex seal will be between the plugs on one housing or the other and if that trailing plug were to fire even accidentally, the next charge would ignite and try to stop the rotor. Very bad MOJO.

 

In boosted engines no split is run at all. It starts to look like a detonation event.

 

Detonation:

 An auto ignition event that starts after and away from the planned ignition location and time. This would be the leading plug fires at (Say) 12 degrees BTDC for a boosted engine. The mixture burns across the rotor face in a smooth rolling flame front and as it does so pressure builds and with pressure comes

heat of compression along with radiant energy from the roaring fire is also heating the yet unburned mixture. So, the combination of heat sources passes by the auto ignition temperature and a second ignition point lights off. This could be a too hot a spark plug tip. A hot carbon spot on the rotor or just a random location.

 

This second event has occurred in a much hotter location and in a higher pressure, superheated mixture. Usually close to an apex seal. In some cases the apex seal will take a few hits like this and not shear off. But not for long. The collision of the two flame fronts can be heard if muffling is adequate. Like a hand full of pea gravel poured onto the hood of your car.

 

Pre-ignition. Any ignition event that occurs before the planned ignition event. They are twin brothers. Preignition leads to Detonation. Detonation leads to Preignition.

 

Download the Racing Beat catalogue. All of this stuff is in there. It is free.

 

Lynn E Hanover

Incinerating rotary

engines since 1980.

 

In a message dated 6/24/2013 10:24:38 P.M. Eastern Daylight Time, shipchief@aol.com writes:

Lynn, Tracy, David and Jeff;

Thanks for your perspectives. Lynn, based on your note, I may have experienced Detonation, plug wire cross fire, high intake temp due to no intercooler, and I may have had the leading & trailing plug wires switched on the rear rotor (tip seal damaged rotor). I noticed that one when removing the engine)

I originally misstated that the rear side housing cracked (it was the front side housing, which is near the fire wall. my bad) But the rear rotor (near the flywheel) broke all the tip seals and may have had switched lead/trail plug wires.

Confused?

I have a TO4E P trim cartridge with .81 AR on-center exhaust housing.    It has a 60-1 compressor. I have been warned that the AR is too tight, so I just ordered a 1.30 AR exhaust housing. I plan to go back together with stock port '87 side housings to get a slightly slower idle (previously street ported). I have 8.5:1 '87 turbo rotors.

I did not set the timing by strobe timing light. 4000 RPM with the tail tethered is too scary for me. That's wailing with no one I can trust sitting in the seat. I set it via the EM2 for best RPM @ about 3500 RPM.

Questions: Tracy,

1)  Does the EM2 fire both L & T plugs at the same time, or is there a difference?

2)  What is the static timing, or some lower RPM timing value I can check without scaring myself to inaction? I would like to check it while cranking over with the fuel injectors and pumps shut off.