The RX8 coils are the only coils on the market
that will fire 9000 times a minute.

The GM LS2 or LS3 or GM truck coils are only designed
to fire 3500 times a minute at the most.
Some are using them on the rotary and there is some
evidence they start having trouble around 6500 to 7000 RPM.

The reason for this  is the four stroke piston engine
fires the plug every other revolution. So 7500
RPM in a Corvette engine the plugs are only firing
3550 times a minute. A rotary fires the plug every
revolution. One reason they get so much power
for the small size of the engine.

I therefore conclude the RX8 coils are our best bet
long term. Mazda had trouble with the early versions.
Some early coils over heated and died killing the engine by
washing off the apex seal oil with raw unburnt fuel.
Poor Mazda had to increase the RX8 engine warranty to
100,000 miles or eight years.

I must say I am not surprised because Mazda was out
there on the bleeding edge with a 9000 RPM
red line and a rotary to boot. Law of unintended
consequences.

Mazda finally identified the problem and improved
the coil (we think) about 2006 to 2007.

Here is a heat sink that should add a bit of long term
reliability.

If you  are running a 2.85:1 gear box I recommend RX8 coils.

Paul Lamar

  Wait a minute, 9000RPM with an 8 cylinder engine is 72,000 sparks
in two
  revolutions. That is 36,000 sparks by the old coils per minute. One
  coil per
  plug with the Pertronix should work.

  Dale Davies

Really? Back in those days we rarely saw 8500 RPM. After
2 hours the Chevy engine was junk with hundreds of cracks
every where including the block.
I was with the Jerry Titus Pontiac TransAm team and we ran Chevies.
Before that I was with Chaparral. The max RPM and life of the
Chevy V8 engine was the same. To get it to go 24 hours
we had to back it off to 7500 RPM and then it was junk
if it even made 24 hours.

Yes I can see how shortening the stroke
will raise the max RPM. The 2.4 L Form 1 V8 with about a 1.5 inch
stroke are turning up to 19,000 RPM. The bore is limited to
3.85" so that puts a lower limit on the stroke.  Each cyl is limited
to 18.3 cubic inches. The area of the bore is 11.64 square inches
so the stroke is 1.57 inches.

But this does bring up a good point. As I recall the distributer
had eight wires for eight plugs and the distributor shaft  ran at
half crank
speed or 4250 RPM times 8 or 34000 sparks per minute. That is 566
sparks per
second or one spark every .00176 seconds. That is 1.76 millisecond.
http://auto.howstuffworks.com/ignition-system4.htm

That is not much dwell time at all. An amazing coil. Perhaps they
were CD systems as I did not pay too much attention to type of
ignitions on
the engines. They came in a crate from GM or the contract engine
builder.
The spark must have been falling off with the points floating.

Now if they were two level distributors with two sets of points then
each set of points had only 4 plugs to fire so the dwell time
would double to 3.53 milliseconds. A more reasonable number.
About what the LS2 is today.

Check my arithmetic. I have been known to make mistakes.

Paul Lamar



Dale,, The petronix 60,000 volt "flamethrower" part number 60130  which
comes with a heat sink is  sold through O-Rileys auto parts looks good
to me for inductive ignition. The second strike CD ignition add on also
uses this coil for the CD spark. With the capability of 60 sparks per
shaft revolution it seems like putting out four sparks for a multi
strike
ignition leaves 8/9 of the revolution idle for cooling.There are also
two lower voltage output models.

george grimes7

"With the capability of 60 sparks per shaft revolution"

At what RPM?

Paul Lamar



Paul,   As I recall the upper limit is 9000  RPM in the catalog on their
web page. As regarding dual point distributors. I have had a bunch
of them. I had  a 1933 steel bodied street rod. First engine was a 325
ci in "super red ram" hemi, then a 354, a 392, and a 440 six pack. All
but the 440 were hemi head types. The dual points were both grounding
the same coil lead. One coil output to the center if the distributor
with 8 leads from the distributor cap to the plugs. The best shift point
was around 6100 RPM and the rev limiter on the six-pack was set to
10,000 RPM. I had valve train including a rev kit on the lifters and
lash springs on the rocker arms which were advertised for 13,000 RPM. I
broke a transmission input shaft (my fault) and the blower turned it to
14,300 on the data sheet before the ignition had time to react. This
engine had a vertex mag with one point set. There was no damage detected
and it was run another 3 years on the same bearings and crank. Two sets
of aluminum rods were changed out but everything else was still in the
car when it was sold.  We sold "Nicky" chevrolet crate engines (427 cu
in L88) as replacements for 396 and 454 engines which the locals were
having trouble with the #3 main bearing web in the block and assorted
breakage.

 I  don't remember any failures or operating problems with these
ignitions and don't recall hearing of complaints from the guys running
301 duntov,and 327 chevy or 289 ford engines which had much higher RPM
operation than my Dodge engines. Intuitively it would seem that a coil
on plug system should be a much lower duty cycle. That makes me wonder
what is causing the problems. The mechanical points back in the day
could operate 4 times per revolution  at a minium of 5000 RPM on a
passenger car. A transistor and most solid state devices can operate in
the Mhz range yet all this high tech stuff seems less capable  than a
car built  50 years ago.

 The first thing I remember changing was the spark plug gap
increasing from .035 to .060 so that might be a factor. There are surely
changes in the core laminations and coil turns ratio of the coil which
is basically a transformer to change to the "high energy"
classification.There hasn't been much discussion about hall effect
sensors/reluctors not being up to the task which would seem to indicate
a reliable signal is being generated.The common thread to the
remaining components is that they are potted into a vibration proof
moisture resistant monolithic block. Some of the components are
apparently convienantly packaged with a heat source(inside the coil)
ensuring  they will have difficulty  conducting heat away  during operation.

 It would seem that a circuit board containing only components
necessary for operation whithout thermal overload checks,  test points,
diagnostic outputs and 1000 lines of assembly language  would be a
better way to go for a fixed advance aircraft installation. The board
would be waterproffed with a minimal coating of clear epoxy for moisture
protection and mounted in a resonable sized enclosure.  A completely
independent system for the railing plugs should suffice for redundancy.
A double pole double throw toggle switch to change from leading to
trailing plugs operation would be the limit of non necessary parts.  The
ignition coil should be one containing only the core and windings of the
turn ratio necessary for 50,000 output voltage. This aparently would be
from an engine which had a distributor ignition.
I don't know how much supurfulous stuff is in the current
circuitry however what seems necessary would be a switched 12v supply, a
resistor to reduce some of it to 5v, 2 hall effect sensors with
capacitors and diodes to trigger the 2  transistors. The transistors and
a large capacitor to operate each coil.

 When I see a circuit board with processors, prom chips , lots
of voltage regulators AD converters,  and tiny resistors and capacitors
I wonder about the flight safety of these things when lightening  and
static electricity come into play. I can understand the complexity when
we are operating sequential fuel injection and mixture control but I
don't buy into the idea that lightning would take out everything so it
doesn't make any difference if the ignition is vulnerable. If the
ignition is the failure point that seems to be something that can be
avoided or reduced by using a minimum of robust components.

george grimes

Those old coils where really big and oil cooled. That may have had
something to do with it.

Paul Lamar