Another oil temp question?

[Roger Lee]

That was my 2006 CTSW and I don’t have it any more. I just took my Drexel tool and trimmed around the opening a little to expose more radiator. It worked well and it was easy to do.

[Tom Baker]

On ‎7‎/‎8‎/‎2018 at 9:51 AM, Tom Baker said:

Roger, the current Rotax Operating Instructions state 266°F with no notation about which coolant you are using. I did a quick look and didn't find the SB you were referring to, could you please post a link?

Roger, maybe you missed this earlier, but I am still waiting on that link when you get time.

[S3flyer]

11 hours ago, Roger Lee said:

Evans boiling point is 375F. 50/50 is around 270-275F.  Evans won’t vaporize at 270F, but 50/50 will so Rotax lowered the max temp of 266F to 248F to prevent vaporization and engine damage. If you are at 235-240F on a climb out the Evans temp penalty will take you over max. Rotax does not want Evans used any more.

I must be missing something.  I get that coolant temp and oil temp are related -- after all we're talking about temperature readings on the same physical engine albeit in different locations and different engine systems.  But oil (Shell Sport plus 4)  is not going to vaporize at 248F since it's flash point is  ~440 F (The Aeroshell Book, Edition 19) so I can't see how 50/50 coolant boiling point matters to the max oil temperature, even though the CHT will definitely impact oil temp.  I would think that the allowable maximums of the two engine systems would be independent.  The 'Rotax Fluids' SB has a note that engine oil temps should be at 250 or below for MOST of the flight.  This implies that exceeding 250 oil temp but below 266 would be acceptable for short period -- like climb.  Also, the latest Operator's Manual (November 2016), Section 2.2 Operating Limits 912 S/ULS clearly states the oil max temperature is 266F and coolant max is 248F.  Section 2.1 is for the 912 UL.

[Buckaroo]

This is goodstuff bye golly!

[Ed Cesnalis]

If 250 were a hard limit my plane would be useless much of the time.  

[Buckaroo]

5 minutes ago, Ed Cesnalis said:

If 250 were a hard limit my plane would be useless much of the time.  

Please elaborate how hot will you let her go!

[Ed Cesnalis]

58 minutes ago, Buckaroo said:

Please elaborate how hot will you let her go!

I've been up to 265 on a number of occasions.

[FlyingMonkey]

13 hours ago, Roger Lee said:

That was my 2006 CTSW and I don’t have it any more. I just took my Drexel tool and trimmed around the opening a little to expose more radiator. It worked well and it was easy to do.

I did the same, it seems to have helped a couple of degrees.

[Mike Koerner]

Buck,

I didn't hear the answer I think you need to hear: pull the power back, lift the flaps, and reduce the climb.

If your engine is getting too hot you need to reduce the power. The heat it produces is roughly proportional to the power so you may need a substantial rpm reduction. The mixture effect is second order.

You also need to get more air flow through the radiator. Lifting the flaps will help you do that.

And with limited power, you’ll also have to reduce the climb rate - to zero if necessary.

Remember that speed is not proportional to power because drag increases as a square of speed. So don't think you can make up for the extra heating at a higher power level with the higher speed that power brings.

On hot summer afternoons at low altitude over the desert, I often have my rpm down in the low 4000 range. I’m not moving quite as fast, but I’m still flying. And I always keep my coolant oil temperature below 220F, even during climbs.

Mike Koerner

 

[Roger Lee]

I think the huge majority here is flying oil temp and not CHT.

Hi Tom,

i went back and re-read some post. It looks like some are swapping the conversation between coolant and oil. I would observe most fly by the oil temp since rarely does the coolant hit mas since the radiator is up front and the coolant behind it. Coolant max temps are 248 with 50/50 and oil is 266, but the huge majority use oil temp as their indicator for their engine temp. Coolant temps are usually down below oil temps. Using Evans makes all temps hotter. The numbers can be found in the Operators manual under the section for pressures and temps for the ULS and in the SB912-043.

I’ve never had a CT overheat on the coolant, but many times on the oil.

[Tom Baker]

2 hours ago, Roger Lee said:

I think the huge majority here is flying oil temp and not CHT.

Hi Tom,

i went back and re-read some post. It looks like some are swapping the conversation between coolant and oil. I would observe most fly by the oil temp since rarely does the coolant hit mas since the radiator is up front and the coolant behind it. Coolant max temps are 248 with 50/50 and oil is 266, but the huge majority use oil temp as their indicator for their engine temp. Coolant temps are usually down below oil temps. Using Evans makes all temps hotter. The numbers can be found in the Operators manual under the section for pressures and temps for the ULS and in the SB912-043.

I’ve never had a CT overheat on the coolant, but many times on the oil.

I think you are right. Someone was confusing coolant temp with oil temp.

[Buckaroo]

7 hours ago, Mike Koerner said:

Buck,

I didn't hear the answer I think you need to hear: pull the power back, lift the flaps, and reduce the climb.

If your engine is getting too hot you need to reduce the power. The heat it produces is roughly proportional to the power so you may need a substantial rpm reduction. The mixture effect is second order.

You also need to get more air flow through the radiator. Lifting the flaps will help you do that.

And with limited power, you’ll also have to reduce the climb rate - to zero if necessary.

Remember that speed is not proportional to power because drag increases as a square of speed. So don't think you can make up for the extra heating at a higher power level with the higher speed that power brings.

On hot summer afternoons at low altitude over the desert, I often have my rpm down in the low 4000 range. I’m not moving quite as fast, but I’m still flying. And I always keep my coolant temperature below 220F, even during climbs.

Mike Koerner

 

Mike you hit the nail on the head on this post! Thanks a bunch! Totally makes sense!

[Mike Koerner]

Buckroo,

I screwed up. I said coolant temperature when I meant oil temperature, as Roger and Tom pointed out. I always monitor oil temperature, never cylinder head temperature.

I'm going to go back and edit my post so it doesn't cause undue confusion for future generations.

Sorry,

Mike Koerner

    

[Buckaroo]

Hey this stuff is all good! I love this forum more than anyone in their wildest hallucinations could imagine! 

This forum has enabled me to enjoy my FD and Rotax more than you could ever imagine! Why? My concerns and questions are always sorted out by very bright informative and experienced people! Thanks everyone!

 

[WmInce]

This forum is a great resource for light sport pilots and anyone who owns a CT (or any other light sport airplane).

Before I actually purchased my CT, I lurked on here for almost a year, gathering information about flying characteristics and mechanical considerations.

Thanks to Andy Walker and Roger Lee, I ended up with a great little airplane (CTSW), at a very fair price.

I just turned 70 and I am still learning and enjoying the journey.

Thanks to everybody who contributes.

[Buckaroo]

12 minutes ago, WmInce said:

This forum is a great resource for light sport pilots and anyone who owns a CT (or any other light sport airplane).

Before I actually purchased my CT, I lurked on here for almost a year, gathering information about flying characteristics and mechanical considerations.

Thanks to Andy Walker and Roger Lee, I ended up with a great little airplane (CTSW), at a very fair price.

I just turned 70 and I am still learning and enjoying the journey.

Thanks to everybody who contributes.

I’m turning 70 this December 9th. In the 70’s and 80’s as a flight instructor who enjoyed teaching I finally quit flying after 5000 hours to do a real paying job with a retirement. Then two years ago I heard about light sport with no medical. I’m a 100% disabled in country Vietnam Veteran who was convinced would never qualify for a flight physical again. Once again energized and motivated to fly again I bought a CTSW. This purchased was the Best Buy I’ve ever done thanks to this forum convincing me to settle on the FD line of planes! I’m really happy with this brilliant aircraft! 

Thanks everyone! 

[FlyingMonkey]

21 hours ago, Mike Koerner said:

And I always keep my coolant oil temperature below 220F, even during climbs.

 

Why?  That seems like a personal limitation that has no practical benefit and a lot of performance drawbacks.

[Mike Koerner]

Andy,

it doesn't seem excessively conservative to me. It's not that much of an imposition and I think engine life will benefit from it.

Mike Koerner

[FlyingMonkey]

12 hours ago, Mike Koerner said:

Andy,

it doesn't seem excessively conservative to me. It's not that much of an imposition and I think engine life will benefit from it.

Mike Koerner

I could not fly in the summer where I live with that limitation.  I’d never see more than 300fpm climb or more than 4000rpm.

Rotax has set the temp limits its engineers consider safe to preserve the engine to TBO, so why change that number?  For that matter, why arbitrarily choose 220F as your limit?  Why not 200F, or 180F?

I see no reason not to trust Rotax design limits, especially if it means hamstringing performance.

[Ed Cesnalis]

12 hours ago, Mike Koerner said:

Andy,

it doesn't seem excessively conservative to me. It's not that much of an imposition and I think engine life will benefit from it.

Mike Koerner

 

37 minutes ago, FlyingMonkey said:

I could not fly in the summer where I live with that limitation.  I’d never see more than 300fpm climb or more than 4000rpm.

Rotax has set the temp limits its engineers consider safe to preserve the engine to TBO, so why change that number?  For that matter, why arbitrarily choose 220F as your limit?  Why not 200F, or 180F?

I see no reason not to trust Rotax design limits, especially if it means hamstringing performance.

I thought about this conversation this morning before sunrise as I took off from Mammoth Yosemite at 7,100 and climbed to 14,000 at 85 to 90kts IAS.  I did much of the climb with my oil at 245*.  Normal for me.

I also thought about Mike as the only cloud in the neighborhood was behind Mt Humphreys

[procharger]

I made an adjustable bracket that goes to the bottom of rad. that way I can

move the bottom of rad. more upright in relation to the cowl, in other words

its much closer at the bottom than it was seems to have helped a lot.It

was hot here today. Ran cooler than it ever has to date.

[sandpiper]

2 hours ago, procharger said:

I made an adjustable bracket that goes to the bottom of rad. that way I can

move the bottom of rad. more upright in relation to the cowl, in other words

its much closer at the bottom than it was seems to have helped a lot.It

was hot here today. Ran cooler than it ever has to date.

Pictures?

[procharger]

No pic its the bracket that attaches the flat bar to the rubber mount to the

engine it has a 180 twist in it I just made one just like factory one just

longer and slotted so I could adjust it also had to loosen rad.hoses so

it can move not hard to do. Bottom left on rad. flat bar about 5 inches long

to the bolt on the side of engine  to motor mount bracket.

[sandpiper]

2 hours ago, procharger said:

No pic its the bracket that attaches the flat bar to the rubber mount to the

engine it has a 180 twist in it I just made one just like factory one just

longer and slotted so I could adjust it also had to loosen rad.hoses so

it can move not hard to do. Bottom left on rad. flat bar about 5 inches long

to the bolt on the side of engine  to motor mount bracket.

Thank you.

[Mike Koerner]

Wow Ed,

The top picture is fantastic. It brings back fond memories of a time when I was still immortal.

But you’re changing the subject.

 

Andy,

After thorough consideration, I think you’re right. The 220F maximum oil temperature I have held myself to is arbitrary. It’s probably slowed me down by perhaps 10-20 knots on perhaps 10 to 20% of the duration of maybe 10 to 20% of my flights (that’s 1/3 of a knot overall). Though sitting here now I don’t regret the needless added hours of flying enjoyment or the reduced fuel costs resulting from this unnecessary conservatism, these were times when I would have otherwise flown faster. And to be honest, every once in a while getting there quicker (like before dark) has been important.

So, from this moment forward, my new personal limitation is 230F.

This is not arbitrary. It is the upper limit of the “normal” temperature range as stated in my operator’s manual. I feel certain the engineers at Rotax did not set this value without careful consideration and analysis. To be sure, the engine will not suddenly fail if you operate it at higher temperatures; even right up to the maximum allowed temperature if you like. But in these engineers’ opinion, running at higher temperatures is abnormal. They would only have included this statement if they expected, or at least were concerned, that higher oil temperatures would result in abnormal wear or reduced reliability.

Mike Koerner