Nope that's not a typo. It surprised me as well, but since oil has
far less heat carrying ability than water, that's what I attributed it to. They
were not calibrated sensors & the gauge didn't have fine resolution, so
that may account for some inaccuracy, but I did swap sensor positions. This
data was during cruise flight after temps had stabilized.
Todd;
Yeah, the specific heat of oil, the
amount of heat it can carry per degree of temperature change, is about 60% that
of water. So it works the other way – it requires a larger delta T for
a given heat load. Typical
oil flow rate at 5000 rpm might be about
10-12 gpm. At a 30F delta T it would carry about 1525 BTU, which is
roughly the heat load to the oil at 140-150 hp. So I’ll stand by
suggestion that something is amiss, because 9F delta T would correspond to somewhere
around 40-45hp.
Of course it’s not a big deal. Your
cooling is fine, and that’s what matters. Maybe the issue is where
you are (were) measuring your oil sump temp.
Actually
I've been so busy flying that I've not had much time for any reports or
discussion, but there is a few things I've noticed. One is that my oil temps
used to lag behind my coolant temps, while now they are very close to the same,
since I've rebuilt the engine. I've been thinking about this and one possible
explanation that I've come up with is;
I used to have my rotors ceramic coated to reduce heat absorption
by the rotor and in turn by the oil, however when I tore the engine down the
ceramic coating was all but gone with only a few traces left. So I assumed that
it had been gone since soon after first start. However now I wonder if the
shock of detonation was enough to cause the coating to flake off ? This would
explain why now I'm seeing ~20F higher temps on the oil than before the
detonation & rebuild? Anybody have any thoughts on this?
Hum-m-m. Could be. Actually,
I’d be surprised if the ceramic coating would make that big a difference,
but that’s just a wild guess on my part. Do you know roughly how
thick the coatings were?