Rotax 912s Temperatures

[bobcharl]

Have various reports of 912s motors having difficulty achieving satisfactory oil and water temps in a reasonable time prior to takeoff. I am considering installing either (or both) an oil thermostat / coolant thermostat to alleviate the problem. Has anyone had any experience with either (or both)?

 

I would appreciate any information.

 

Thanks,

 

Bob

 

 

[Kyle Communications]

Hi Bob

 

I have the water thermostat I got from the guy in the USA John Gilpin has one fitted and it works really well. I have not fitted mine yet as I have been a bit slack but seeing winter is fast approaching I better do it. I also need to block off some of my oil radiator for winter as well. My temps are a bit low the oil temp only ever goes over 90 deg C when on a big climb also I don't think I have ever seen the water temps over 105 usually sit around 95 or 100 this everyone tells me is a bit low. Keep us informed on what you find

 

 

[Mick]

I think there are some Evektor Sportstars that have an oil thermostat fitted, I have not heard anything about them though.

 

 

[Ultralights]

i just cover part of the oil cooler, even at -4 OAT, oil was 90 deg, and coolant sat around 75.

 

 

[bobcharl]

Thanks for the comments guys.

 

Mark, I have read JG's comments on oil temp and it seems he didnt find a thermostat improved warm up time noticeably, presumably because while the thermostat reduces flow from the cooler it does not reduce flow from the oil tank which seems to operate like a tower cooler.

 

UL, did you find that covering part of the cooler didnt reduce warm up time even though it raised in-flight temp?

 

To confuse the issue further, I spoke to the Rotax rep at Natfly who said if I were to read the Installation Manual thoroughly enough I would find that Rotax do recommend an oil thermostat, and yes they do,(for operation at low temps). This fellow also made the comment that while he felt that oil temp at t/o was much more important than cyl. head/coolant temp, he could see a benefit in a coolant thermostat to limit temp drop during long glides.

 

I will do some more research before deciding what to do.

 

Bob

 

 

[Kyle Communications]

Hi Bob

 

The trigger for when you can go is the oil temp should be at least 50 deg C then you can go

 

 

[Ultralights]

warm up times havnt changed much, oil has to be minimum 50 degC so it flows properly through the filter without causing resistance

 

 

[gregrobertson]

I spoke to Wall when he was at Bert Floods about this. His recomendation was that the oil temp should reach 100 deg at least once on each flight to boil off any condensation in the oil. I try to run mine on 105 deg and CHT on 105. Does not always work out that way. I have seen the oil temp thermostats and they seem to work OK but add quite a lot more pipework under the cowl.

 

Greg

 

 

[cscotthendry]

I spoke to Wall when he was at Bert Floods about this. His recomendation was that the oil temp should reach 100 deg at least once on each flight to boil off any condensation in the oil. I try to run mine on 105 deg and CHT on 105. Does not always work out that way. I have seen the oil temp thermostats and they seem to work OK but add quite a lot more pipework under the cowl.Greg

And more stuff to possibly fail. And WEIGHT!!!

 

 

[facthunter]

That's the point.More to go wrong. They do take a while to warm up. Having synthetic oil means you just have to make it and you will be OK. I reckon a cable operated louvre for the radiator would be the trick, because they are sensitive to OAT's. Nev

 

 

[bobcharl]

Thanks All,

 

Was aware of the requirements re 50 deg and 100 deg. I was really trying to find a system of reaching t/o temps quicker in the cold morns we get here in southern NSW.

 

Thanks again,

 

Bob

 

 

[Ultralights]

isnt the oil temp measured on the cold side of the oil cooler?, so the oil temperature will be well over 100 deg before it enteres the cooler if it is at 90 deg after its cooled.

 

 

[Powerin]

Back in the 70s we had a tractor of Czech origin (with all the trimmings of an eastern bloc manufactured tractor). I remember vaguely that it had a very simple cable/gravity operated plastic radiator blind which we, of course, never used in our Aussie climate. The cable simply pulled a roll of plastic up over the radiator.

 

Here's a pic I found of something similar on an old Lanz Bulldog tractor. Maybe something that could be adapted for an aircraft?

 

 

 

[rankamateur]

Back in the 70s we had a tractor of Czech origin (with all the trimmings of an eastern bloc manufactured tractor). I remember vaguely that it had a very simple cable/gravity operated plastic radiator blind which we, of course, never used in our Aussie climate. The cable simply pulled a roll of plastic up over the radiator.Here's a pic I found of something similar on an old Lanz Bulldog tractor. Maybe something that could be adapted for an aircraft?

 

Wouldn't it flap a bit?, don't think the lanz bulldog ever approached stall speed let alone takeoff speed.

 

 

[gregrobertson]

Try one of these. http://www.winnmicro.com/wab/tundra.html It wouldn't take much to make it cable operated from the cabin. It could solve all the problems. You could probably do something similar for the oil cooler.

 

Greg.

 

 

[Guest Maj Millard]

Frankly running a bit on the cool side doesn't seem to be any problem for them. I fit half covers on both oil cooler and radiator in cooler months, and remove only the radiator one in warmer months. By the time I'm strapped in and organized in the cockpit ready to go, plus run-ups, mag checks, taxi and line up, it's been five minutes since start up. The temps come right up after take off, so no dramas.

 

Don't see why adjustable coolant flaps wouldn't work for you colder guys, but wouldn't you think they would have them in Europe by now if they were really needed ???...Limiting some air-flow through your cowl is guaranteed to work also.............................Maj...

 

 

[Ultralights]

ive never had a problem with just 1/3 of oil cooler covered pretty much permanently, water cooler i never cover, never needed to, the only time i have uncovered the oil was when i was out broken hill way in summer. all winter in zero deg temps, never needed to cover water cooler, ut oil definately yes. no real need for a manual operated cover.

 

 

[alf jessup]

Hi BobI have the water thermostat I got from the guy in the USA John Gilpin has one fitted and it works really well. I have not fitted mine yet as I have been a bit slack but seeing winter is fast approaching I better do it. I also need to block off some of my oil radiator for winter as well. My temps are a bit low the oil temp only ever goes over 90 deg C when on a big climb also I don't think I have ever seen the water temps over 105 usually sit around 95 or 100 this everyone tells me is a bit low. Keep us informed on what you find

My water & oil temps were a little on the low side i felt in the Tecnam Sierra (75 water and about 70 oil) , as the plane had glycol as coolant I changed it to Evans NPG waterless coolant as reccomended by Rotax and bingo 100 water and 85min oil, prolonged climb to 8500 to cross the great divide in 37 deg day max water temp got was 120 deg and oil 115 @ 80kts climb, very happy with the change.

 

Alf

 

 

[Planechaser]

I toyed with the idea of an oil therm, but it is so much easier to tape up 1/3( and up to 1/2 in peak winter! Desert mornings!) of the oil cooler. Especially as an oil therm will not speed up the morning warm up time, so I have been told.

 

I can't see that a few extra clamps and pipes would change the reliability terribly much. When put on from new it all looks very visible and so easy to check for leaks. I have not had an oil pipe leak in 600hrs and I have no reason to believe thermostat piping would be any different. Extra pipe liability is the argument the Jab/O-200 blokes use. ;)

 

I have been told that the aftermarket oil filters have a faster flow and so the warm up times are reduced, but I do not know the brand, and have not tried it. Higher oil flow in a filter the same size says less filtration to me, but may be I was being a bit of a nanna about it...!!

 

6min is my average to get oil to 50C; 10min in the longest I have ever waited.

 

I also agree that oil temp is measured on outlet of the cooler so you are always reading on the cool side.

 

 

[facthunter]

It doesn't make sense to be cooling oil that you are trying to heat up. I worry about thermostats .Something more to go wrong. Your basic engine can be brought undone by the "extras". as well as a "major" fault, so keep it simple. HAVING SAID THAT... I always favour some way of manually regulating the cooling. You will reduce drag as well as get (and keep) your engine temps where they should be. Nev

 

 

[bones]

It doesn't make sense to be cooling oil that you are trying to heat up. I worry about thermostats .Something more to go wrong. Nev

That is the whole purpose of the thermostat, is to keep most of the oil out of the cooler until it reaches the right temp to open the thermostat.

How many times has your thermostat in your car failed?, and also even if the thermostat did fail it doesnt block all the oil it still lets approx half through, so you will have hot oil but it might not be over the max, good bit of gear in my mind anyway, i use them all the time never had a problem, and as for the weight, they weight maybe 1/4kg if your that close to your limits i think you got bigger issues.

 

Now for water temp dont worry about the cooler the better, it is only the heads that are being read, so the cooler the head the better the combustion nd ie fuel burn/comsuption.

 

well thats the way i think of it anyway, my 2 cents worth

 

 

[Alasdair]

I use an oil thermostat and find that my warm up times have dropped considerably, particularly on our cold sub zero mornings. I have found that my oil seldom gets to 90 degrees though and must blank off a bit of my cooler in the colder months. My EGT,s are well below operating limits as per the manual

 

 

[DrZoos]

Have you thought about running less oil in the tank. And changing it more often.. Less volume takes less time to heat...and will run warmer ..

 

 

[alf jessup]

Have you thought about running less oil in the tank. And changing it more often.. Less volume takes less time to heat...and will run warmer ..

Also takes longer to cool down Dr Zoos,

 

Manufacturers have a max & min quantity limit for a reason.

 

Alf