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Engine Oil Temps


Runtoeat

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I flew Ziggy (N9922Z) yesterday in hot (95F) temps for the first time. On climb out to 5500' my oil temp was approaching redline. It appeared that I the temps would probably stabilize around the redline but I didn't want to test this theory so I throttled back to keep temps around 240F. What do you guys out West do? You fly constantly in this environment for most of the year, don't you? My CTSW is a 2006 and does not have thermostats for oil or coolant.

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Dick,

 

I have had the same oil temp issue for years. (my EFIS overheats as well. recently the EFIS overheated just from sitting on the ramp in the sun. I had to use its cooling fan to bring it down to temp during pre-flight)

 

The big question is; are these high readings correct? I'm still not sure in fact I think the gauge is at fault.

 

If ambient temps are above 70F I will see oil temps in the yellow. I have learned that I spend less time warm/hot if I just climb to the cooler temps and get it over with.

 

My CT does seem to stabilize a few degrees below redline. Worst case was departing North Las Vegas when over 100F on the ground, climbing away from the runway at redline over the city is un-nerving.

 

I've planned on putting a digital thermometer sending unit in my oil tank and then running the display in the cockpit and comparing temps on a hot climb.

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Hi Guys,

 

You can help this out by adjusting the needle in your carbs to be just a tad richer. You pop the top off the carb, pull the slide out and take the needle out. Then move the clip down one notch. This in effect raises the needle itself and allows just a tad more fuel. This helps in the cooling of your engine. My engine never gets that hot anymore. All off my temps across the board went down. Fuel usage only changed maybe 2 tens of gph. This isn't hard. If you don't like it then put it back, but it works well for me.

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Roger,

 

My CHT temps run nice and low even when oil temps get high. Also I fly regularly at high altitude, I realize that rich is relative but I wouldn't want to get overly rich. Lastly my plugs always look good.

 

If my CHT was high as well the extra fuel would make more sense to me.

 

 

 

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Charlie Tango and Roger, good thoughts on this subject. I remember jetting my Husqvarna's (250 wide ratio enduro) bing carb to get proper mixture and forgot how effective this can be in regulating engine temps but CT has a good point regarding good CHT temps indicating that mixture might not be the cure. CT, I like your idea if putting a remote temp sensor in the oil reservoir. If you placed the sensor in the return flow, the oil temps you see should be pretty close to the internal engine oil temps. Let me know how this works for you.

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my EGT (like my CHT) is always in the green and always on the cool side. before the rotax i used EGT as a guide for mixture and given the cool temps i get i would be leaning not enriching.

 

my big picture calls my hot oil readings into question.

 

 

 

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Summer has finally arrived here. Two days ago my radiator was still taped and It was almost impossible to get 220 oil temp. Now, tape off, level with 5000 rpm it sits at the bottom of the yellow which is 230. OAT was 88 degrees.

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Some high oil temps can be caused by a small kink in the oil line that reduces flow and just making sure your rubber air deflection skirts around the radiator are in the correct position after you replace the cowl. The oil line under the engine that goes back into the tank would be one to look at or suspect on our plane.

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  • 1 month later...

I have the high oil temps similar to Ed, and we have discussed this a lot on the other forum. I have recently found that if, instead of throttling back like I used to do, if I keep full throttle in and raise the cruise climb speed to about 95 knots, then I can keep the temps around 240 on a hot climb. - WF

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  • 1 month later...

One idea on the oil temps that I think someone has tried and which seems interesting: The heater shroud around the muffler exits on the top front side, where a big wad of heater hose wiggles around to the heater intake on the back. If we could relocate the output on the heating shround on the muffer to the back part, there would just be a short piece of hose taking it to the heater intake, I bet the oil radiator would get better air flow and help with this issue. We have been having temperature inversion in LA lately: 60F on the ground and 90F at 3000 feet. I have been hitting 240F on temp the oil by 2500 feet in the climb. WF

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We are seeing late 80's on the ground just lately and into our hot season. Air is very dry and hot and I'm also finding it difficult to keep my oil temps below 250F. I looked at what you are saying and it makes sense.

My question, is why do most other Rotax installations have the oil cooler seperate from each other?

I have checked the return to the oil tank and the pipe was hanging a bit onto the odd up in the air straight in to the tank. I think this should at least have a 90 degree elbow for ease of routing.

 

Regards

 

Bruce

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Hi Bruce,

 

Being at 85F shouldn't have you up in the 250's for oil temp. First prop rpm can play a big part here. What is your engine rpm at WOT flat and level at 1000' AGL? It should be 5500. If it is lower then that is part of the problem by over working the engine. Next take off a little flatter and a little more speed. Keep it full throttle, the engine runs cooler here than than if you cut back to 5000 rpm to climb. Try to keep the engine at or above 5000-5200 on take off. I live in Arizona and our temps get a lot hotter. The three things i listed above should make a difference.

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I have a Neuform three blade constant speed and set 5500 for take off. Flat and level at 5500 I run high at about 240F. I keep to 500fpm at 80kts.

I,m sure your temps in Arizona get hotter than ours, we see an absolute high in the shade of 115F. Last summer we had a DA of 9000ft at a field of 3700ft. Only good for lying in the pool with a cold beer I guess! So yes we are at the start of spring and that is why I'm trying to get better cooling before it really heats up.

 

Bruce

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Hi Bruce,

 

Looks like our seasonal temps in Arizona and South Africa are very similar. Try setting the prop to run 5500 max WOT flat and level then pull back on the throttle to 5200 and see if that doesn't help the higher temps. It won't be much more than 10F-15F though. Leave the prop set at 5500 WOT and don't change it once. Then take off. You will only see about 5000 rpm on take off, but see if that doesn't help on take off temps a little. Use zero flaps and at least 80-85 knots on climb out. I know this setting is not fully utilizing your constant speed prop, but it might help your temps a few degrees. The last thing to do here is to richen the fuel mixture if the above doesn't work. Pull the tops off the carbs and move the clip on the needle down one notch. You do not need to take the carbs off, just pull the top off and take the slide out. This will help cooling some.

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  • 5 months later...

Ed has always questioned if is oil temps are reading right. I have the same problem as his: high oil temps in the climb but chts stay cool. By now I have switched out the oil temp. sender and the oil temp guage in the panel and I get the same readings. I think in my case they are real. WF

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  • 2 months later...

It will get a little richer as the throttle opens, but once it is closer to wide open the the main jet controls the full flow. Once the throttle is wide open the needle really isn't in play. So where we fly around 5000-5200 rpm it is in play and will allow you to be a little richer and a little cooler in the EGT's, oil temp and CHT's. I found mine last summer approximately 15F cooler in oil temps and CHT's and about 80F in EGT's These numbers are approximates and your personal, results may be a little different. Prop pitch plays a part here because it can load or unload the engine slightly and change temps a little, along with OAT's and density alt.

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OK, so if the problem, like mine and Ed's is hot oil temps (and normal CHTS) in the climb, normal to slightly elevated (say 240) oil temps in cruise, this may not make much difference. Still looking for a magic bullet on this problem. WF

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Hi Wayne,

 

In the summer months 220F-240F will be normal. There is no magic bullet for your normal temps. OAT, home elevation , prop loading, ect... all play a part. If you drop from 240F to 225F with a needle change that's a pretty fair change and very normal. If you want to make a change do the needle, take off with zero flaps and a much flatter higher speed climb.

 

 

 

p.s.

What air filter are you using? What oil are you using?

 

 

240F in a climb during the summer is normal and don't give it a second thought. The actually max temp for the engine is 266F and your well below that.

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I will let the oil get to 250F in the climb, and it will hit and even exceed that on a hot day (30C OAT or so) even in a 100 knot flaps -6 slow climb (which is over 5300 rpm the way my prop is set). Last week doing it that way, at 28-26C OAT, it took me 30 minutes to get to my 8500 foot cruise from sea level. At 250F on the oil I power back, level off for a while and step climb once it cools back to 240. This works, but it sure would be nice to just climb on up to altitide at 85 knots. It still puzzles me why some of us have this problem and others do not. WF

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