Hello all,

This is in regard to the spark plug cool that is being discussed. I came
across this on the RX7club.com site. I pleasantly surprised to see the
amount of technical experimentation that some on this board try. I send
the good nuggets I come across.

http://www.rx7club.com/showthread.php?t=751977


Rob Woods

Interesting thread. So far it has been unnecessary to modify the rotor housings
for rotaries used as aircraft engines. These guys may be at the 150 to 200 HP
per rotor level. Here is a trick all should do if they get a chance.
It relives any steam pockets that may be generated around the spark plug area.

Also the  3rd gen water pump and RX8 water pump are less than ideal.
The Rx8 in particular as it is much smaller than the 2nd gen water pumps.
Somebody is already making a better impeller for the RX8 engine but I have not
tracked it down yet.

The bottom line is you need to know what is happening and the only way
to know that is measure the "cylinder head" temperature with thermal couples
embedded in the roto housings.

Paul Lamar
--

Hi Paul,

Yes very interesting threads, and great pictures, but in all of the seven
pages I could not find one mention of the amount of power and the power
loading verses time these engines were putting out. In short their duty
cycles.  We can easily cool a 400 hp 13B NA with one ice cube if it is
only running for 15 seconds:)

When at Seven Stocks last week I asked Jim at Racing Beat the following.
"For un boosted 13B aircraft engine, putting out 300hp for five minutes
on take-off and 200 to 220Hp. continuously,   assuming adequate heat
exchangers sizing, what would be the recommended cooling flow needed
through the engine?"  He said about 45 gallons a minute.  He also said
I wouldn't get those flows with a Mazda engineered pump.  This is quite
logical when you think about it.  Mazda sized their pumps, and designed
their cooling systems for AUTOMOBILE applications and lower duty cycles
than we will demanding of our aircraft engines.    For optimized
hp/weight aircraft engines enhancing flow as well as heat transfer is
mandatory.  Peppering the engine with thermo-couples so that we can
confirm our modifications are functioning is the only way to safely fly
these engines.  Our Mazda engine aircraft applications presently have a
real lack of documented performance data - a fact that doesn't help
promote the engine as a good alternate to traditional choices.

Doug in Japan

With all due respect to Jim we have 2nd gen 35 GPM pumps cooling 240 HP
3 rotors with no problems so far. If anybody cares about this they
should be installing thermo couples to measure the metal temp
within one mm of the combustion chamber adjacent to the lower
spark plug. The only people doing this is Mark Seitle with his 3 rotor
and he reports no problems with reported metal temperature well
under the 500 F limit.


Paul Lamar

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