On Thu, 23 Feb 2006 21:07:36 -0500, "Peter Dohm"
wrote:

"Drew Dalgleish" wrote in message
...
Just read the kitplanes article on electronic ignitions. Is anyone
here flying with an e-mag p-mag combo that would like to share their
experience. Does it really make more power and any service or
instalation problems. Thanks Drew

Well, I probably shouldn't be the one to try an answer, since my experience
is limited to a quick look at the EMagAir web site a few minutes ago. But
since no one else has come forward, I'll try from a purely theoretical
perspective and a little knowledge of cars long ago...

At full power, there should be no change; because the timing should be the
same as on your old magnetos. And my presumption is that the purpose is a
system upgrade, rather than to repair a deficiency in the current ignition.

Assuming that you connect the MAP sensing, there will be a spark advance as
you reduce manifold pressure and, therefore, the engine should produce
slightly more torque for a given combination of RPM and reduced manifold
pressure.

Therefore, with a constant speed prop--where you manually adjust RPM and
manifold pressure according to a table and then lean by EGT--you should
receive a slightly faster cruise and possibly slightly lower fuel
consumption.

In the case of a fixed pitch propeller--where manifold pressure is rarely
even monitored and cruise power is set entirely by RPM--the improvement
should be entirely the result of reduced fuel consumption. In some
installations, you may be able to achieve a higher RPM at some altitudes
without exceeding the maximum--yielding a result similar to that expected
for a CS prop.

I have no opinion as to whether any resulting higher power output is harder
on the engine, about the same, or even slightly easier...

I hope this helps.

Peter

I'm considering repowering my murphy rebel upgrading from an 0-290 to
a 0-320 clone. one of the options I'm considering is an electronic
ignition instead of new slicks. The cost isn't much but I'm not sure
if it would make much difference with my low and slow plane. The prop
will be fixed pitch probably a prince composite prop to keep the
weight down.