Bring down oil temperature on a 912 Vz

How do you guys determine the coolant temperature? My plane (which I bought and didn't built) only has temperature sensors for two cylinder heads. These are never hot, at all times below 75° Celsius (167°F). Is that a good indicator or do I need to get a coolant sensor and if yes, what temperatures would I want the coolant to have?

Till Middelhauve wrote:

How do you guys determine the coolant temperature? My plane (which I bought and didn't built) only has temperature sensors for two cylinder heads. These are never hot, at all times below 75° Celsius (167°F). Is that a good indicator or do I need to get a coolant sensor and if yes, what temperatures would I want the coolant to have?

I think this question has been discussed before.

If aged memory serves - Rotax recommended temperature range is what the cylinder head sensors read (not what the coolant temp may get to elsewhere in the cooling system).

In short your engine is running far to cold.

Again from memory the recommended, cruise,  coolant temperature is in the 90-100 C range, not over 120 C 

It's about the same for the oil, with a recommendation to get to over 100 C for a period (usually in climb) to drive off undesirable volatile fractions.

An internal combustion engine needs to be operated at optimum temperature, for most efficient combustion, least wear and for liquids to perform at their best.😈

Sean Griffin is right. Rotax does state a minimm oil temp of 50 C and max of 120 C (122-248 F). I don't know where you got the recommendation to never exceed 100C. As previously stated you definitely do want to get the oil over 100C at least for a bit to boil off any water that may have condensed in the oil.

Cylinder head temperature should also stay under 120C (248F)

One of the things I like about an oil/water heat exchanger is that it generally keeps both pretty close to the same value. 

The recommendation about the temperatures I should run the engine on are from the Italian supplier that altered the original 912 to be a turbocharged 135 hp engine (as described here: https://www.912turbokit.com/copia-di-fly-120hp).

I am well aware of the differing numbers from Rotax and this supplier. What would you do if you get two opposing sets of numbers to aim for?!? They tell me to aim for 90° and not exceed 100°C ever. Ignore and follow the Rotax numbers?

I am about to fit an oil thermostat that will make sure the oil doesn't run through the oil cooler below 85°C and will fit a bigger oil cooler to keep the oil below 100°C.

"I am about to fit an oil thermostat ....."

I Dont see any harm (other than complexity, weight & cost) nor can I see any benefit.

Your stated problem is high temperature - thermostat will do nothing to mitigate this.

Sam Purpura suggested an intercooler

Others , rethinking/engineering your air flow through the cooler/radiator

Fitting additional/larger systems may achieve improved cooling or not, at significant expense - go KISS first and if that doesn't work start spending 😈