CHT temps

[K5054]

Hello all,

 

I have recently changed my oil cooler in new (150hours) rotax 912ULS as the temps were slightly high. Oil temps are now good but the CHT’s are higher than before (expected) due to positioning.

 

my engine has the newer CHT limit of 120°

 

my question is are these temps ok. Or should I be concerned and try to lower them?

 

(°C)

 

OAT    CHT.     OIL

 

17°        94°      88° (Cruise)

 

22°      100°     90° (high speed cruise)

 

20°      110°    105° (extended climb)

 

my CHT temps used to be 70-90°

 

 

[Downunder]

110 is pretty hot for 20 ambient. (You will struggle on a hot day)

 

You haven't got the wires the wrong way around somewhere?

 

Your cht looks like my oil and vice versa.....

 

My oil always matches my cht temp at least (thermostat installed) or my oil is hotter.

 

 

[K5054]

No wires are the same. With the bigger oil cooler the radiator has less area/airflow than it did

 

 

[Downunder]

Ok, I see.

 

To me, I wouldn't generally want to see lower than 90 oil temp in regular/fast cruise but your overall oil temps are good. (Ideal temps 90 to 100) 100 to 110 in climb not a problem at all.

 

I think your cht temps are too hot really....

 

I think they should be equal to or lower than the oil...

 

 

[K5054]

Ok. Might have to put smaller oil cooler in. That will bring temps back down I think

 

 

[facthunter]

Oil temps should be 85( Plus a bit). IF you are on synthetic you can get a bit hotter now and then without worry. Too cold and the oil will carry water and have  a cloudy appearance. Head temps are usually considerably hotter depending in whether liquid cooled or aircooled and  WHERE is the sensor located? Liquid cooled engines usually run head temps LOWER than ideal due to the boiling point of the coolant used and other characteristics of the cooling system, like hot spot formation, Pressure cap fitted, altitude flown at  You Cap is a diff to ambient Density altitude, so the higher you go the less pressure on the coolant and the boiling point lowers.

 

 Air cooled  limit temps are usually metallurgical properties related generally where if they get hotter the aluminium loses it's heat treatment advantages . (Hardness and strength.) the limit figure to stop this is around 235 degrees C. Once this happens the change is permanent. It might look OK but it isn't.  Another limitation is caused by how the engine itself handles the high temps, like detonation and lubrication problems and  non metallic connections neoprene gaskets etc When a plane lands with high head temps the heat from the hot parts may easily cook the core and damage seals and cause Carbon formation Nev