Oil Temp never gets in the Green

Hi Gene,

You're on the right track. With OAT's around 40F your oil temp probably won't get very high. A huge amount of us just use some thin 2" wide aluminum tape across the the cooler and or radiator. Easy and quick to apply and easy to just yank it off. Oh and did I mention it's cheap to do. 😀

I'd like to know why 100% of all liquid cooled piston engines built in the last 130 years use thermostats, except Rotax. This 100's of billions of engines in every car, truck, train, heavy equipment, ship, and boat, but Rotax thinks tape over the radiator is a good idea. Tape - too hot on climb out and too cold in cruise and descent.

Hi Ben

The major difference is this is an engine with only liquid cooled heads, not cylinders.  As such the engine is not as prone to cold seizure like the "billions" of engines you refer to.  Ships, trains, heavy equipment almost exclusively use diesel engines so they don't really count in my mind.  

I have never seen any reference from Rotax about tape, that is simply not true.  I am pretty sure what Roger is referring to is the practice of most operators to work around the issue rather than develop winter kits like we see on GA aircraft for cold weather operations.  A correct design of the cooling system would not need that.  Perhaps talk to your kit supplier or OEM for the aircraft.  The specs call out the temperatures not how to achieve them. Just my opinion. 

Cheers

Rotax Wizard, thanks for your reply and opinion, but I don't see anything in your response that answers my question, why are there no thermostats on Rotax engines? 

I don't see why air-cooled cylinders and water-cooled heads makes any difference. Does that fact somehow make wild temperature swings good for the engine? I have been teaching engines and power mechanics for nearly 50 years at 4 and 2 year colleges and I have never heard of "cold seizures". Is Rotax thinking that everything is good as long as the engine doesn't seize up due to running too cold? I also don't see why the type of fuel (gas vs diesel) makes any difference either. And even if you eliminate the diesels from the comparison does that mean the number of gasoline engines is insignificant? I do agree with you that the cooling system design is the problem - it needs a thermostat. What cooling system design are you thinking about that would eliminate the need for a thermostat? Someone told me that thermostats are unreliable, I doubt that anyone who has ever owned a car would agree. When was the last time anyone replaced a thermostat on a car, maybe 1967? I have read that Rotax makes the pistons and cylinders out of similar material giving them similar expansion rates, I am sure it helps the engine survive without a thermostat, but running at a consistent temperature is good for any engine.

It sounds like others are trying to cover for Rotax, why is that? Its ok if someone were to say "I agree that there should be thermostats, and I don't know why Rotax doesn't want, like, or approve of them". If there is a good reason, I would sure like to know.

Hi Ben,

My comment on tape is what some do that don't have oil and or coolant thermostats. It's just a different simple inexpensive way. There are many Rotax owners that do have them and many that do. These aren't sent directly from Rotax because there are tons of different installations and regions around the world that may or may not need them. This is left up to the aircraft Mfg's and owners. Plus most thermostats only open up at 180F. This is no different than auto, motorcycle and any other engine / vehicle mfg. No company can supply what each and every owner individually wants. Then there are people like me who don't particularly want a thermostat.

Bottom line is if you want one there are some on the market and you can install one providing you don't have to have an approval from the mfg.