In a message dated 5/23/2006 9:27:40 A.M. Eastern Daylight Time,
lors01@msn.com writes:
John did tell me that the threshold of 'splutter' was around 38" Hg
MAP. Since the engine quickly went down hill even at lower throttle
settings and he thought it was only running on one rotor at the end of
testing, I suspect there are a lot of clues to what is wrong other than
the 'splutter' at 38". We just don't know what they are. The
coils being bad is a long shot since it would mean that two of them died at
once, not likely but possible.
Did the engine run well after cooling for some time? Not enough
information.
One quick check for secondary ignition breakdown, is to quickly install two
new plugs in the leading holes, gapped at .010". If the problem is still there,
it is less likely the secondary output. If the problem is gone, it is likely the
secondary output.
The lost spark coils of later RX-7s fire twice per revolution. They fire
both of the leading plugs twice for each revolution. So they work with very
short rise times. At 6,000 RPM that's 12,000 cycles per minute. Try that with a
Corvette coil.
Even so, ignition problems at 6,000 to 6,500 RPM should not be happening.
We shift at 9,600 RPM, and with two MSDs even going a bit lean at the top causes
a minor misfire or skip. Re-gap the plugs to .010" fixes that every time.
Also reducing throttle setting slightly restores good ignition performance
when this is the problem.
Stock Rotary engine coils are very good. The lost spark coils are
better.
Using two lost spark coils, one for both leading and trailing on each
housing would be as close to bullet proof as is possible. The trailing must be
distributed otherwise.
If Tracy's controller can light a stock (lost spark) coil, that is.
Lynn E. Hanover