I recently began observing that shortly after I shut down my 915iS the manifold temperature climbs into the red (which starts at 50 - I saw it hit the high 60s when this first happened). When the engine is running, however, there are no high temperature indications at all (although I do note that the manifold temperature is the first to cross into the yellow if I'm climbing at full power on a hot day). The temperature is consistently in the normal range when I shut down (after giving it a couple minutes at idle), but then ramps up over 5-10 minutes.
* If I put a fan on it immediately after shutting down, I can mitigate it such that it stays out of the red - I've been doing this as a precaution.
* The ambient temperature has been around 90F (32C) - I'll be interested to see if there's a change in behavior as the weather cools off.
* It's hard to say if it's a new phenomenon, since prior to this I wasn't normally turning the aircraft back on to check the gauges again in that timeframe.
I discovered this as a consequence of an aborted take-off which turned out to be directly caused the failure of a weld on the exhaust manifold, and I initially hypothesized the two were related. But the fact that even moderately high intake manifold temperatures are relatively low compared to normal exhaust temperatures leads me to question that initial hypothesis. Intake air at > 50C may be problematic for a running engine, but what about when the engine is not running (if the engine is restarted, the temperature drops into the normal range quickly once air is flowing through the intake)?
My regular mechanics say they haven't yet seen enough 915's to have a good feel for them. So just how worried should I be? Do other 915's exhibit this behavior? Is my trick of air cooling it with a fan after shut down a reasonable interim remediation? Or, alternatively, unnecessary? What might be a better solution? And might this be indicative of any broader problem?
Greatly appreciate any input on the matter!
