Low Cylinder Head Temps

Ted Christopher · #1 05-16-2016, 10:08 AM

On my last flight I was seeing the warning for low cylinder head temps, during level flight (not windmilling.) Air temp at ground level was about 45 F. The cabin heater, when I turned it on, was putting out mildly warm air. I have 41 hours on this new in December RV12. Any ideas-do I need a mechanic to check an engine coolant thermostat?

tomkk · #2 05-16-2016, 10:45 AM

Go to the RV-12 forum and use "Search This Forum" for "Radiator". There'll be a number of threads about cold weather or winter flying.

I live in Florida so it's not a problem here but we flew up to the D.C. area last November. Temp on the ground was 25*F and something like 5*F at altitude. We froze our tushes off and I made a removable, adjustable baffle as soon as we got home that I'll use if I ever do that again.

Sink · #3 05-16-2016, 10:48 AM

There is no minimum CHT for the Rotax 912. It only cools the heads from overheating.

Those with thermostats may get to see it up around 180F, but if the OAT's are cold enough that could be affected too. You could ignore the CHT low temp alarm, reset your instrument to reflect a lower alarm temp (most common) or see why the thermostat isn't keeping it higher.

So long as the oil temps are up in the proper range no problem with the CHT's.

RFSchaller · #4 05-16-2016, 11:43 AM

Are you sure it's not an indication problem? A guy I know with an SLSA RV-12 had his CHT indications go low due to connector/ground issues.

Mich48041 · #5 05-16-2016, 12:00 PM

Do RV-12 Rotax engines have coolant thermostats?
I went flying yesterday in similar conditions. The CHT was about 175-180. What was yours?
Of bigger concern is the oil temperature. 190 degrees is good. Thinking that spring was here, I had removed the winter oil-cooler baffle a few weeks ago. Yesterday the oil temp only got up to 170. I should install a Thermostasis.

PilotBrent · #6 05-16-2016, 12:17 PM

Most of the legacy Rotax 912 engines have cylinder head temperature probes on two of the four heads. "Newer" 912 heads have the probe moved to a slightly different location that apparently better measures the coolant temperature as it passes through the head itself. I believe the normal temperature range for that setup is different than the legacy location, so you need to know which you have to confirm the proper range for engine monitoring.

Elsewhere on VAF the "Bender Baffle" is described (for E-LSA/E-AB) modification. Those that installed that mod, rave about it. I use a more simple option. I have a rectangular piece of aluminum and Velcro to place in front of the coolant radiator in winter months. I actually have a larger (3/4 coverage) and smaller (1/2 coverage) version depending upon how cold it is outside. Easily installed and removed before flight. On Saturday I had it on for an early flight, but found one of the head temps just touching the yellow zone on one climb out, so I just removed it at my next stop and tossed it in the back of the plane. Will reinstall this Fall if it stays warm up here in the east. Certainly makes winter flying more tolerable, but on a really cold day, its really hard to squeeze warm air out of the Rotax.

JBPILOT · #7 05-16-2016, 02:27 PM

If you install my "Heater Damper Door", you can get very good heat even in cold weather. I force the CHT's up to 205 - 210, and very warm air comes out. Also helps warm the oil. I have a Thermostasis unit also, but a warm block warms the oil more also.

Ted Christopher · #8 05-17-2016, 03:18 PM

Quote:

Originally Posted by JBPILOT

If you install my "Heater Damper Door", you can get very good heat even in cold weather. I force the CHT's up to 205 - 210, and very warm air comes out. Also helps warm the oil. I have a Thermostasis unit also, but a warm block warms the oil more also.

I'm amazed by the information you all provided, this is just the second time I've been to the forum and I've learned lots already. Thanks, I'll record both oil and CHT temps next time I'm up and refer to your different posts.