Hot or Not?

[FlyingMonkey]

It's the height of the oppressively hot and humid Georgia summer, and I just wanted to check in and see if my temps are normal for the conditions.

 

The other day I was flying at 1800ft MSL in 93-94°F OAT.  In cruise at 5200-5300rpm, my oil temp was 240°F.  Going faster raised it a bit, slowing down didn't seem to help much.  It was pretty steady about 240-242°F depending on engine rpm.  I'm sure I could have climbed up to cooler air and been fine, but given conditions I would have had to make a slow and/or step climb.

 

Yesterday in 88°F OAT at ~1500-1800ft MSL I was seeing around 230°F much of the time at 5000-5200rpm.  I slowed down to keep pace with my buddy in a slower plane at 70-80 knots and 4000rpm, and my temps came down to 200°F or less.  Speeding back up made them creep back up to 220-230°F (by then the sun was going down and it was cooling a few degrees).

 

A week or two back I was taking off to fly home in later afternoon from a fly-in.  OAT 91-92°F, and in a climb at WOT the temp was 240-245°F.  I climbed to 4500rpm where the OAT was around 72°F and leveled off.  My temps slowly came back down and settled around 215-219°F.

 

 

So what do ya'll think?  Yes it's been very hot here, and the humidity makes it even worse.  But my temps feel a little on the high side, but that might be paranoia talking.  Opinions or suggestions?

[Ed Cesnalis]

The other day I was flying at 1800ft MSL in 93-94°F OAT.  In cruise at 5200-5300rpm, my oil temp was 240°F.  Going faster raised it a bit, slowing down didn't seem to help much.  It was pretty steady about 240-242°F depending on engine rpm.  I'm sure I could have climbed up to cooler air and been fine, but given conditions I would have had to make a slow and/or step climb.

 

...

 

 

So what do ya'll think?  

 

 

I think you are as limited as I am you just don't have big mountains right in front of you.

 

Look at poor Wayne step climbing for an hour to get out of the LA basin.

 

We have to get to 10,000' fast, like in 20 minutes to make it over the mountains and depart the area.  Step climbing doesn't work because you don't get relief till you find lower temps at altitude.  You are throttled back and over 240, what if you needed full power to get over the mountains?  You would have the same issue we do.

 

We all need higher capacity oil coolers if we want to operate under 230* in hot summer conditions.

[Roger Lee]

240F is not too hot to climb, but should go down when in cruise down around 5200 and your prop pitch set correctly.

The are only a few of you that have high temps compared to roughly 1800 other CT's. Are you sure your temp on your panel is correct and not just off 10-15 degrees. Time to quit blaming the coolant radiator and find the real culprit. The rest of us don't have overly high oil temps. If all you see is 230-245F in a climb during the hotter summer months then that isn't that terrible and should come down in cruise. Temps are also affected by take off technique.

 

ED,

 

I know you like to run WOT at 5500 in cruise. Is that all you can get or can you get to 5600-5650? If that is all you can get at WOT then you need less pitch to help unload your engine. Running at WOT versus 5200 rpm in cruise also produces more heat.

 

 

 

A bigger cooler is a bandaid for another issue

[FlyingMonkey]

Roger, if you were asking me:

 

1) My prop is well pitched, I can get 5600-5700rpm at WOT down low.  I usually cruise 5200-5400rpm.  at 5400rpm I usually see 124-127kts TAS.

 

2) My temps do come down at cruise at altitude.  The main problem is when cruising down low at 90+ OAT where I will see 230-240F at 5200rpm.

 

3) I don't know that my oil temp gauge is correct, but how would I check?

[Tom Baker]

The temp probe placed in boiling water would be a start.

[Roger Lee]

The senders have specific ohm readings at specific temps.

You can open the cowl opening some to allow more air flow too.

[Ed Cesnalis]

Roger, if you were asking me:

 

1) My prop is well pitched, I can get 5600-5700rpm at WOT down low.  I usually cruise 5200-5400rpm.  at 5400rpm I usually see 124-127kts TAS.

 

2) My temps do come down at cruise at altitude.  The main problem is when cruising down low at 90+ OAT where I will see 230-240F at 5200rpm.

 

3) I don't know that my oil temp gauge is correct, but how would I check?

 

 

I used to have different configurations for climbing until I learned there is no relief until I climbed to an OAT below 75*.  Your CT sounds exactly like mine except mine has to do big hot weather climbs all the time.

 

I've checked my oil temp gauge by getting a digital meat thermometer and putting the probe in the oil tank with a duct tape temporary lid. The wire was long enough to go out the door in the cowling and in the vent in my door.

 

The meat thermometer not only confimed my gauge it reacted very quickly to temp changes due to retarding the throttle and decending.

[Ed Cesnalis]

ED,

 

I know you like to run WOT at 5500 in cruise. Is that all you can get or can you get to 5600-5650? If that is all you can get at WOT then you need less pitch to help unload your engine. Running at WOT versus 5200 rpm in cruise also produces more heat.

 

A bigger cooler is a bandaid for another issue

 

Roger,

 

My only other issue is that I demand more out of my engine, just like Wayne for the same reasons.  We have to climb steep in hot weather to get over the mountains.  Wayne literally had to spend and hour climbing recently, that's ridiculous.  Wayne's a smart guy and I'm at least persistent.  If there is another issue that makes our cooler's capacity more than adequate your welcome to come out and show us, we haven't found it in 8 years of trying.

 

I have had many years now of you trying to change my cruise RPM and prop pitch.  There is one and only one compliant way to realize maximum available power at altitude for more than 5 minutes.  

 

• Motivation - when maximum available power falls below desired power due to altitude a partial throttle is only a further reduction in power.
• Pitch for more than 5,500 and throttling back is an example of reducing power when all available power is desired.
• Pitching for less than 5,500 and even at WOT is the other way to make available power un-access able.

Bottom line Roger is I opperate where as little as 50hp available and in serious terrain and it would mean to operate with even less power if I was to take your advice.  This argument is getting old, your advice changes over time but the maximum power setting remains fixed.

[gbigs]

It is worthwhile to note that summer flying esp in the West will mean yellow temps on climbs.  The factory says it's okay and actually helps burn off water that may be in the oil.  The key is once at cruise the temps should stabilize...if they stay yellow in level cruise there is an issue, even if flying at 75f oat.

[Ed Cesnalis]

top of my green arc is 230, redline is 266

 

In the winter I can climb in the green, in the summer I climb in the yellow, in the summer I cruise in the green as long as I climbed above the high temps.  -  this isn't too bad.

[FredG]

Andy, your temps are higher than mine.  At 80 degrees F, 5200-5300 rpm cruise, I will see 200 degrees F oil temperature.  At 95 degrees F,  5200-5300 rpm cruise, I may see 210-215 degrees F oil temperature.  

 

Plane:  2006 CTsw, stock Rotax 912.

 

I fly with a friend who has a 2007 CTsw, his temps are very similar to yours (and are consistently higher than mine).

 

Tom's suggestion to check calibration of the temperature sensor with boiling water makes sense to me.

 

fg

[rhanson]

The senders have specific ohm readings at specific temps.

You can open the cowl opening some to allow more air flow too.

Roger,

Would you elaborate on the open the cowling suggestion,

Do you mean loosen fasteners, or remove something else ?

 

RH

135ct

[Doug G.]

Roger has talked about this before. Her is talking about the opening in the lower cowl that allows air to the radiators. He had talked about using a Dremel to create a larger opening.

[Roger Lee]

The CHT probe and the oil temp probe are the exact same and can be swapped to double check temps.

You need to make sure the coolant radiator is as centered as it can get and not off to one side or pulled back too far. It can be adjusted side to side and if you look behind the radiator it can be moved fore and aft.

If you want to open up the cowl opening then it is usually the bottom lip that is hiding more of the radiator. I used my Dremal to open the bottom lip a lot more exposing more than auditor to air flow. I did this with the cowl in place so I could see what I was doing.

[FlyingMonkey]

IIRC Roger, the bottom lip folds in toward the radiator, I presume to provide stiffness/strength to the lower cowl.  About the only way to make the opening larger at the bottom would be to remove the "lip" at the bottom.  Is that what you did?

[sandpiper]

Mine is another one that gives problems with heat. On an 80 degree day I might be able to get 4000' AGL before I have to back off. If I level off and hold 5200 it takes a really long time to come down. If I hold 5000, then it comes down reasonably fast.

 

The first summer I had the plane, pitched from the factory for 5300 full throttle and level, I did not have these issues. Issues started in summer #2 after i pitched to 5600. Maybe I should go back to 5300??

[Ed Cesnalis]

Mine is another one that gives problems with heat. On an 80 degree day I might be able to get 4000' AGL before I have to back off. If I level off and hold 5200 it takes a really long time to come down. If I hold 5000, then it comes down reasonably fast.

 

The first summer I had the plane, pitched from the factory for 5300 full throttle and level, I did not have these issues. Issues started in summer #2 after i pitched to 5600. Maybe I should go back to 5300??

 

Sometimes I think I'm crazy but you confirm my memory.  I got about 2 years, it was the 2nd McMinville fly in which was during a heat wave that I first saw high oil temps.  They started on the way to Oregon from Mammoth cruising at 10,000' I was in the yelow (above 230) and had a 5 hour cruise in front of me.  I saw high temps in Oregon as well, climbing out of Tillamook I had to climb slowly to avoid 266 degrees.  What is going on?  Until then I could climb as hard as I wanted and remained at 230*.  What suddenly changed?  Never figured it out just like so many others.

 

John,  I did have a period of time after re-pitching until the high temps began.  I don't think going back fixes it and even if it does that means giving up a lot of power, I would rather get a larger cooler.

[Roger Lee]

A larger cooler won't fix it if you can't expose it to the air flow and it may not fit under the cowl. You need to check your existing cooler/cowl spacing and then see if the larger one would fit. Then you would need to open up the front of the cowl more for the air flow which you could do now.

 

If your temps changed all of a sudden then that's exactly what I mean to fix. Over pitching at 5200-5300 WOT causes more heat. That's a fact, it lugs the engine and caused stress cracks in the case with the mid 2006 and earlier engines.

 

If you had a sudden temp change then something changed it. Putting a larger cooler in is a band-aid to an existing problem.

 

 

Ed,

 

I have never changed my thought and theory on prop pitch and engine.  I still remember on the old forum when you declared "Woodstock comes Alive".

 

 

If this were my plane I would pull all outward oil system parts and hoses off. All hoses (replace with new), oil pump (Inspect and clean), add springs to hoses,

re-route oil hoses (especially the one off the bottom of the engine going back to the tank), hot flush or replace the oil cooler, open up the front cowl opening.

[Ed Cesnalis]

Roger,

 

The upgraded cooler has  more rows but the same physical dimensions.

 

All the fixes you suggested I have had done.  That was mostly fixing things that weren't broken.

 

Here's the way I see it.  Some of us put extra demand on our 912ULS cooling because of big mountains and high temperatures. And some of the fleet no longer cools like new with no fix resulting in new or desired level of performance.  Even flight design saw the need to upgrade the cooling when extra demands where presented like in their deliveries of float and tow planes.  We are looking to upgrade to the same cooler that FD uses with the same dimensions. If you can buy the FD part its absurdly expensive if you assemble your own coolers its pretty cheap.

[Roger Lee]

Hi Ed,

 

Wayne's demands are no different than mine. Yours are different than most everyone else here on the forum due to your field elevation and Mnt. range clearance. During the hot summer months my climb to 8-9K may be up to 230-240F, but drops to 218-220F at 5200 rpm cruise. No big sweat. One thing I definitely do is climb slower than most I'm usually not in a hurry to get there. A 10-15F difference between planes is quite small and can easily be a probe, instrument, wire connection, ground, pilot technique, hose placement and or cowl opening alignment.

Is your "S" turn oil return hose still coming up from behind the engine? If so buy a 90 degree hose fitting and bring it out straight up around #2-4 cylinder. You will need to loosen the large Banjo bolt and rotate it on the bottom of the engine. That makes it a straight shot for oil return. A slow oil return will cause extra heat.

A 15F difference in planes can easily be just a slightly slower oil flow.

 

There is something that needs fixing if your plane sees 250-260F. Either the plumbing, the prop or pilot technique. I

[Ed Cesnalis]

My hoses are re-rerouted already.  I haven't seen anything above 250 since recent improvements.  

 

I fly to Southern California, departing Van Nuys I my initial climb is 9,000' starting from high southern CA temps.  This exactly what Wayne has to face all the time.  I think the climbs in CA can be more demanding in that you have to climb steep. 

 

Don't you think 8 years of chasing this is enough?  Its to the point where all the fixes have already been done.  What if a well broke in ULS sometimes runs hotter?  Whats the big deal to switch out a little 1.5lb cooler?

[sandpiper]

I'm just venting when I talk about return to 5300. Won't do that. Also, I did reroute the oil hose from bottom of engine,. Did not help.

 

I think I will trim some off the cowling on lower side of the opening. If it looks like it might crack I'll reinforce with fiberglass.

[Roger Lee]

"Don't you think 8 years of chasing this is enough?'

 

Only if you chased the right thing. After 8 years maybe it's a thing you over looked?

 

You still have to ask yourself why only a few with all the rest not having the same issue.

What's different and what changed. The few said there was a change after a while. What was that?

[Ed Cesnalis]

If you can find the problem I'll gladly fix it.  I have employed all of the fixes thtat you have suggested and I still want the bigger capacity cooler.

[gbigs]

We flew at 5350 rpm top in cruise.  Never a need to run the engine higher than that... We never burned 100LL and switched to Full Syn Mobil 1 motorocycle racing oil and the temps were never an issue (this oil is made to control temps at high RPM)...it is entirely possible to keep the temps down in summer in climb if you simply climb at 62 kts or so.