Using stock Mazda
coolant O rings and exceeding those temperatures would indeed compromise the
O rings and you end up with coolant in your combustion chamber and/or
combustion gases in your coolant galleys I know - as it happened to me as
well as others when first sorting out my installation back over 10 years
ago.
However, once we
found and substituted TES (Teflon Encapsulate Silicon) coolant O
rings with a much higher temperature rating, and Viton seals for the oil ring
seals, it became quickly apparent that a lot of the problem with
elevated temperatures had been the O rings and somewhat higher
temperatures could now be sustained without any apparent damage or
problems. Not to say, higher temperatures are recommended, but many of
us have found brief excursions above 200F do not cause any detectable
problems.
My normal cruise
coolant and oil temps are within 5F of each other and normally range from 160F
to 185F at cruise depending on power levels and OAT. So as a percentage
of operating time, my temperature excursions are on the order of 1.6% of my
total engine operating time. On a hot 90+ day, I will exceed 200F during
climbout until I hit 120 MPH IAS usually a brief period of from 2-3 minutes
before airflow catches up with heat being produced.
Numerous rotary
installations now fly with red lines above what would have been prudent
if using the older stock Mazda O rings. I have over 8 years on my
installation with TES O rings, Tracy Crook over 15 years the vast majority
of it with the TES O rings. So until we get some aircraft with
over 2000 hours on an engine (and set of TES O rings), we really wont know
whether these brief excursions are resulting in accumulated ill effects or
not. If it takes 2000 + hour to manifest itself then I am not
concerned.
There is no question
that the rotary can not, for the reasons mentioned by several, with stand the
temperature ranges of most piston engines however, we are not quite as bound
by earlier limits (at least for limited time periods) as we once were.
Thanks to sturdier seals.
We had 8 rotary
powered aircraft at the Texas Rotary Round up and it would be interesting to
know how many have exceeded 200F and any heat associated problems.
Although most have less than 500 hours, so not a true indication of what to
expect one way or the other
Time changes,
technology advances and improvements are found.
Ed