CHT temps

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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Warmi
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CHT temps

Postby Warmi » Sat May 26, 2018 8:28 pm

My EFiS ( TruTrak) has CHT warning range set to ...yellow between 240-245 and then goes into red at 245 and up.

Well, predictably, while climbing out at 95F outside temp,and after waiting in line for about 10 minutes on the ground , my CHT went into 240s ( yellow ) and then briefly hit 246 - all that while I was still trying to reach pattern altitude.
The usual remedy, lowering the nose and shallowing the climb, worked just fine but I am wondering how other folks EFIs warning ranges are set up , or rather simply, at what CHT temp do you actually take some action to lower the temps ..240... 245?

Interestingly , my oil temps never go into yellow , just the CHTs...
Flying Sting S4 ( N184WA ) out of Illinois

TimTaylor
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Re: CHT temps

Postby TimTaylor » Sun May 27, 2018 12:24 pm

This is one reason why I prefer the Continental.
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3Dreaming
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Re: CHT temps

Postby 3Dreaming » Sun May 27, 2018 1:21 pm

TimTaylor wrote:This is one reason why I prefer the Continental.


Temperature issues are more often a airframe related issue than an engine brand issue. I know of several Continental engines that have oil temperature issues. I know of one in particular that the oil temperature will reach red line in about 10 minutes of hard flying with outside air temps above 85°.

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Re: CHT temps

Postby TimTaylor » Sun May 27, 2018 1:40 pm

3Dreaming wrote:
TimTaylor wrote:This is one reason why I prefer the Continental.


Temperature issues are more often a airframe related issue than an engine brand issue. I know of several Continental engines that have oil temperature issues. I know of one in particular that the oil temperature will reach red line in about 10 minutes of hard flying with outside air temps above 85°.

Of course you do. In flying Continentals and Lycomings for 54 years, I've never had an overheating issue. Who doesn't have over-heating issues flying Rotax in the summer? I flew the Remos 2 1/2 hours a couple weeks ago and could never get out of the yellow. It's the nature of the engine and cooling system.

Why do you feel compelled to refute everything I post? Weird. Please put me on your ignore list.
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Re: CHT temps

Postby Wm.Ince » Sun May 27, 2018 3:03 pm

TimTaylor wrote:Why do you feel compelled to refute everything I post?
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Re: CHT temps

Postby roger lee » Sun May 27, 2018 3:41 pm

Quote:
"It's the nature of the engine and cooling system."

No it isn't. It's poor setup, poor take off techniques and poor understanding of the engine and poor understanding of what the numbers really mean. Sometimes it's the aircraft MFG's fault for poor setup. Some owners have their max and minimum values set wrong. When done right my FD CTSW would never get over 235F on a hot summer day in Tucson, AZ. Then drop down to 218F in cruise.

The 240F's is no big issue. So long as you try not to go over 250F then you're okay. Once level then it should go down. 250F should be red. Up to that is yellow and that's okay. I find many oil hoses under the fire sleeve flattened which reduces flow which raises temps. These can be opened with a spring placed inside the hose to keep it open. I just had an FD CTLSi (fuel injection) with a flattened oil hose.
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Re: CHT temps

Postby TimTaylor » Sun May 27, 2018 3:58 pm

Wm.Ince wrote:
TimTaylor wrote:Why do you feel compelled to refute everything I post?

Do you ever have anything of value to add or just jump on the Tom Baker band wagon?
Last edited by TimTaylor on Sun May 27, 2018 4:06 pm, edited 2 times in total.
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Re: CHT temps

Postby TimTaylor » Sun May 27, 2018 4:00 pm

roger lee wrote:Quote:
"It's the nature of the engine and cooling system."

No it isn't. It's poor setup, poor take off techniques and poor understanding of the engine and poor understanding of what the numbers really mean. Sometimes it's the aircraft MFG's fault for poor setup. Some owners have their max and minimum values set wrong. When done right my FD CTSW would never get over 235F on a hot summer day in Tucson, AZ. Then drop down to 218F in cruise.

The 240F's is no big issue. So long as you try not to go over 250F then you're okay. Once level then it should go down. 250F should be red. Up to that is yellow and that's okay. I find many oil hoses under the fire sleeve flattened which reduces flow which raises temps. These can be opened with a spring placed inside the hose to keep it open. I just had an FD CTLSi (fuel injection) with a flattened oil hose.

All I know is there are numerous post and threads on the internet about Rotax over-heating issues. I have never seen any regarding Continental or Lycoming engines nor have I ever experienced any. Say what you want, but Rotax engines in LSA frequently have over-heating issues, and that's what the OP is asking about. I guess a Rotax in a SkyCatcher would never over-heat because the Continental doesn't.
Last edited by TimTaylor on Sun May 27, 2018 4:14 pm, edited 3 times in total.
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Re: CHT temps

Postby TimTaylor » Sun May 27, 2018 4:01 pm

TimTaylor wrote:This is one reason why I prefer the Continental.
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Re: CHT temps

Postby Warmi » Sun May 27, 2018 4:09 pm

If 240 -245 during climb out is OK then I am OK .... it only occurs during steep climb outs and goes away within 1 minute or two as soon as I level off.

My original post was basically inquiring more of what constitutes a reasonably green/yellow/red setup range for CHTs for Rotax engines - it seems every installation comes with different numbers :)
Flying Sting S4 ( N184WA ) out of Illinois

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Re: CHT temps

Postby dstclair » Sun May 27, 2018 7:33 pm

248 is Max (Red), 241 - 247 is yellow.

My Sting hit the yellow CHT once after sitting out in a sunny 95F day for a couple hours before I fired it up. I hit yellow just as I was lifting off. Went back to green pretty quick during my cruise climb. This is with 10 1/2 years of ownership.

Do you still have your heater muff attached? This will make a few degrees difference.
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Re: CHT temps

Postby Warmi » Sun May 27, 2018 7:43 pm

I just took it off today for the first time but I can’t test it cause they closed my airport for a few days ( the runway buckled up due to heat right in the middle as I was about to land yesterday - I was damn lucky...) The NOTAM about it showed up on my Garmin Pilot a few minutes after I landed - getting this info out that fast was pretty darn impressive.

Hopefully taking off the muff will help a bit ...Sting S4 is supposed to have better air flow around the engine ..or so it says in the marketing materials :)
Flying Sting S4 ( N184WA ) out of Illinois

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Re: CHT temps

Postby dstclair » Sun May 27, 2018 8:13 pm

It is better than the S3 and Sport for oil cooling. The cowl has much larger air scoops. I've not noticed CHT differences from those S4 owners I know, though. YMMV. That being said I've never had oil temps beyond ~250F and that was a climb out of Tulsa with ground temps around 110F and air temp never dropping below 90F for a 2 hour flight. Oil temp was stable at around 235F that particular flight with CHT's in the green. Short answer is -- there is no issue with the Rotax installation in a Sting for cooling.
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Re: CHT temps

Postby Warmi » Sun May 27, 2018 8:42 pm

I actually have never seen oil temps get above 232 F , even on the hottest day - it is CHT temps that I have to watch for.

When it is above 85 F , a sustained steep climb of about 1300 feet at 65 knots and full power will almost always result in CHTs reaching 243 or so - leveling off will bring these down to 230s within a minute or two.

Last fall, after bought the plane I had my mechanic replace Evans with antifreeze - I actually had problems with plane running really cool during winter months (couldn't reach 200 F ) but now it is back to being hot - will see what difference getting rid of the heater muff will do.

Thanks for your insight.
Flying Sting S4 ( N184WA ) out of Illinois

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Re: CHT temps

Postby 3Dreaming » Sun May 27, 2018 10:18 pm

TimTaylor wrote:
3Dreaming wrote:
TimTaylor wrote:This is one reason why I prefer the Continental.


Temperature issues are more often a airframe related issue than an engine brand issue. I know of several Continental engines that have oil temperature issues. I know of one in particular that the oil temperature will reach red line in about 10 minutes of hard flying with outside air temps above 85°.

Of course you do. In flying Continentals and Lycomings for 54 years, I've never had an overheating issue. Who doesn't have over-heating issues flying Rotax in the summer? I flew the Remos 2 1/2 hours a couple weeks ago and could never get out of the yellow. It's the nature of the engine and cooling system.

Why do you feel compelled to refute everything I post? Weird. Please put me on your ignore list.


I have owned 3 CT's, and none of them had temp issues even in triple digit outside air temps.

I have never felt the need to put anyone one on the ignore list. As long as this is an open forum I will feel free to quote anyone I please, as long as I feel I can contribute something of value.

In your 54 years of flying Continentals and Lycomings you never had an overheating issue, that you knew of. Knowing about the issue is the key. In the last few years engine monitoring has gotten much more accessible. Often times when modern engine monitoring is put on old airplanes like you used to fly with no issues, it reveals that CHT temps are much higher than anyone had previously thought. Often times they were very close or exceeding limits set forth in the engine operation manual. Most of the Rotax engine installations use modern engine monitoring, so comparing them against older aircraft without the monitoring is not a fair comparison.

In my 35+ years as a pilot and mechanic I have been around many different airplanes, standard category, experimental, and S-LSA. The same model of engine in one airframe compared to an other has a completely diferent temperature profile.


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