Since all I can do from here is speculate, I will speculate. Combustion
upsets from ignition faults would be more than occasional. Same for a constant
too lean or too rich situation.
So, perhaps it is caused by Too hot a heat range in the spark plugs. Try a
set of Autolite AR2592 gapped at .015". Or the NGKs in dash 10 heat range or
11.5 heat range. Yes it is very tight, but try it anyway. Nobody will stock
these plugs. Need to be an overnight order from Autozone or similar.
Use inductive plug wires, if any. Fire both leading and trailing together.
No split timing. No low voltage ignition wires anywhere near a high tension
wire
If you have a peripheral exhaust port, excessive back pressure can
occasionally force burning gasses into the intake. This causes a profound
misfire. It will not go unnoticed. A Renesis probably has no such problem.
No overlap between intake and exhaust.
A blast tube on the coils.
Reduce timing to 20 degrees. Good up to 9,000 RPM.
There was a picture of an exhaust header a few days back, where one tube
entered a down tube at a 90 degree angle. This is very bad MOJO. Ideal header
design requires two header pipes be the exact same length. Joined at the same
shallow angle (Long collector) Header lengths in multiples of 12 inches.
If you get a misfire at full throttle, try retarding throttle slightly to
see if that cures the problem. If so, it is usually a secondary ignition
problem.
Gap the plugs tighter and try again. If the problem is cured, then the
ignition voltage is marginal for the layout in use. Gap all of the plugs tighter
all of the time or use a higher output ignition system.
The reason this gag works is this. The higher the cylinder pressure, the
more energy it takes to get a spark to jump the gap. Reducing the throttle
setting lowers cylinder filling, and cylinder pressure goes down a bit and the
plug start firing again.
The racer uses NGK R6725-11.5 The 11.5 is the heat range. The higher the
number the colder the plug (in the NGK system).
These are gapped at .010" Both leading and trailing fire together.
Both are powered by MSD6AL with rev limiters. Works great up to 10,000
RPM.
A single rotor face misfiring is more like a thump and nothing more,
(at higher RPM) your problem sounds like a cross fire or exhaust cross
fire. Very pronounced and can cause broken apex seals and sheared off alignment
dowels or cracked out alignment dowel holes in the rear iron. Also very bad
MOJO.
Lynn E. Hanover
Yes, it is happening
at WOT, 2000 ft, 5800 rpm. Staging was long
past.
Bill
B