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.
Yes, it is happening at WOT, 2000 ft, 5800 rpm. Staging was
long past.
Bill B