The famously cool 912

[danny_galaga]

People often say the Rotax 912 seems to cool TOO well at times. Of course that is better than the reverse. 

With that in mind, my plane isn't yet flying and I'm just running the engine each weekend to keep things dry and oiled up.

 

Because there's not much load, and the weather is getting a smidge cooler it's not easy to get it warm enough. My engine has two oil coolers, the same size and one radiator. Last week I taped one oil cooler up, and it didn't make a difference. Today I went further. I taped up BOTH coolers and half the radiator. It finally went from just under 90° to nearly 95° 😄

 

Obviously, in reality I haven't blocked 100% of the oil cooling because there will be air turbulating behind each cooler, taking some heat away. And needless to say, I fully understand if there was a proper load (taking off) I would soon know about it with all that taped off 😂

 

Still amusing though. It will stay taped off for now, so I don't have to run it for 30 minutes trying to warm it up.

[Reynard]

The 912 is used a lot for glider towing in Europe and that is when they will run hot. Some designs incorporate a pilot operated blind on the oil cooler.

 

[skippydiesel]

I concerned about so much ground running, especially if the engine oil is not getting above 100C for a sustained period (say min of 20 mins).  Not convinced you are doing good things for the engine.

 

I suggest removing all fuel, with special attention to the carburettors. Hand cranking the engine to circulate the oil. If not flying for a  long period, say 6 months +, doing a full engine preservation eg plugging all possible air entry points, overfilling/flooding crankcase with oil (no engine rotation). 

[facthunter]

Rotax would have a recommended technique for short and long term storage.   Nev

[facthunter]

IF you have a new Motor don't run it till you have to. Nev

[skippydiesel]

50 minutes ago, facthunter said:

Rotax would have a recommended technique for short and long term storage.   Nev

From faulty memory - Rotax has a long term storage recommendation. To the best of my understanding, no engine manufacturer recomend/approves  frequent short duration nil/minimal load running.

[facthunter]

If you have a powered Glider or standby power unit you cannot avoid  less than ideal operating conditions. Historic vehicles are a good example. People leave their plane parked outside the clubhouse and then taxi it for a few minutes near dusk to the Hangar  and leave it for weeks. One of the worst things you can do to a motor. It takes about 45 mins of high cruise to warm the motor to a temperature which will reduce condensation in the oil.. More frequent oil changes are recommended under such conditions or use an oil like aeroshell 100 Plus to reduce Camshaft and follower scuffing and pitting in lycomings.  Nev

[danny_galaga]

Motor on condition. If new I definitely wouldn't run it until taxi trials. 

[pmccarthy]

My new engine (80 hours) has never seen the green band on either the oil or coolant gauges. It worries me. Smart air, the Foxbat agent, say it is normal. I would mask off part of the radiators, but am not convinced that the problem is not just the gauges. I need to get serious about diagnosis.

[danny_galaga]

12 hours ago, pmccarthy said:

My new engine (80 hours) has never seen the green band on either the oil or coolant gauges. It worries me. Smart air, the Foxbat agent, say it is normal. I would mask off part of the radiators, but am not convinced that the problem is not just the gauges. I need to get serious about diagnosis.

Do you mean the needles aren't even moving UP to the green band? 😲

 

Now that's cool! Needles are moving though?

[pmccarthy]

The needles move just a bit. Highest I have seen them was a long climb on a hot day, got about half way up the yellow band. Never seen them reach green. Really good cooling or dud gauges. Oil just lifts off the stop after 3 or 4 minutes from cold start, coolant doesn't move. Photo shows typical cruise. Been that way since new aeroplane.

 

 

 

Edited March 25 by pmccarthy

[danny_galaga]

Hmmm, my only thought was maybe it was the wrong range gauge, but they look like 150°, which is what the Rotax sensors are. Which water sensors are wired? The front or the back? If the front, you may be able to swap the oil and water wire around. They are pretty close. They are the same sensors. See what happens then. Or if the back sensor is wired you can still put the oil wire on the front sensor. I did this recently to see if my oil sensor was ropey (it was)

If the gauges behave differently after that, that is an indication something is up. 

 

Also, I used one of those thermometers that you point at objects and pull the trigger to get a sense of what's happening. A guide only because those temps will be quite different to the sensor temps. 

[pmccarthy]

Thanks, good ideas.

[facthunter]

Don't know why they would be a lot different.  Plenty of people use them for checking pre heat assembling parts and welding. Nev

[danny_galaga]

1 minute ago, facthunter said:

Don't know why they would be a lot different.  Plenty of people use them for checking pre heat assembling parts and welding. Nev

It's all about the angle you hold your tongue etc with those 😄 . But it helped me get my head around the front cylinders being a different temperature to the back cylinders. 

[facthunter]

Anyhow IF you run too cold the Oil will show a whitish Hue on the dipstick. It's one of the worst things you can do to an engine, wear and sludge wise. Get onto a failed thermostat fast. (in a CAR) . It's one of the reasons Taxis' do such high miles..   Nev