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Aircraft Boats: What's Your Normal Operating Oil Temp.?

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rick

rick

Administrator
My straight valve Lycoming (h2ad-160hp) runs between 150-160 degrees.

I've always thought cooler was better, but I'm finding some articles on the internet that claim your engine can't get rid of the condensation it creates if your running below 180-200 degrees.

Here's one of the articles: The Ten Biggest Lies About Piston Aircraft Engines (Lie #6)

I'm kinda thinking about taping up my oil cooler a little to get the temp up to 180.

What do ya'll think?
 
Rick, my first thought is to make sure that your temp gauge is accurate ... that the temp you're seeing is in fact right. It could be reading a little low, in which case you sure wouldn't want to blank the cooler.

Ken
 
Did you notice the comment about the H2AD at the end of lie #1 Rick? Where does you temp gauge read from, before the oil cooler or after? That could make a difference of up to 20-25 degrees on oil temp.

Larry
 
Rick,
I found this on the net also.


CYLINDER HEAD TEMPERATURE
Lycoming says that cylinder head temperatures should never exceed 500 deg.F, but for maximum service life, cylinder head temperatures should be maintained below 435 deg.F during high performance cruise, and below 400 deg.F during economy cruise. High performance cruise is 75% power and 150 deg.F on the rich side of peak EGT. Economy cruise is less than 75% power and leaned to just above roughness. These temperature limits assume down draft cooling and temperatures measured at the bayonet location under the cylinder, which is the hottest side with downdraft cooling. For updraft cooling (like we have) you need to correct for the temperature difference across the cylinder, so add 40 deg.F to the reading in climb and up to 70 deg.F when leaned in cruise. If you are measuring CHTs with thermocouples under the bottom plugs, the temperatures are approximately correct without correction. If you are measuring CHTs with thermocouples under the top plugs, subtract 40 deg.F from your readings to make them comparable to bayonet readings on the hottest side of the cylinder. So if you are using bayonet sensors on the bottom of the cylinders, your indicated temperatures should range from 300 deg.F to 350 deg.F. Clear?


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OIL TEMPERATURE
Oil provides about 1/3rd of the cooling of an air-cooled Lycoming engine, and high oil temperatures can contribute to high CHTs. Lycoming says the desired oil temperature with OAT in the 0 to 70 deg.F range is 170 deg.F, and in the 30 to 90 deg.F range is 180 deg.F. The maximum allowable oil temperature is 245 deg.F, but I would never be happy with it much over 180 deg.F. With an 0-360 engine, you might get by with a 9-row cooler if you duct the cold air to it, but a 13 row cooler works like a charm. We have a 13 row cooler and our oil temperature runs 170 to 180 deg.F almost all the time.



http://www.cozybuilders.org/newsletters/news

Ken
 
rick,

I went through this issue when I first came to SAO. I was amazed at the low oil temps and the lack of any particular cooling on the airboat. I called Jr Jurnigan on these issues. You should call him too. I am not going to quote him because I can't remember all of the background information.

I will say that everyone does not agree on this issue. I came away feeling that the airboat application is a severe use application.

Take a look at this old thread. Hogman9832 is running his engine the way I think it whoud be run: (a little warmer on the oil in the winter would be good)

http://www.southernairboat.com/phpBB2/viewtopic.php?t=230&highlight=shroud

jim
 
I could be wrong and this is just an opinion. But sort of what I have seen and heard.

Aircraft are typically moving at 80 mph (often at up to 140mph) at a higher altitude. That means the air is always a few degrees cooler. Even when it is in the 90s, if you climb to 5000 feet, the temperature drops several degrees. That combined with ram forced cooling through the cooling ducts surrounding the engine and directed air directly through the cooling fins. This makes a system that will pull quite a bit of heat very effeciently from the cylinder heads and the oil cooler. The air has turbulence from going through the ducts, but there are typically no dead spots where air does not flow well. Also, the ducts force air supposedly evenly over the all cylinders. Unlike an airboat with seats and other things making strange flow over the engines and the second (and third and fourth if present) are getting air that has already past a hot cylinder in front of it and is tumbling. Aircraft actually have the duct work altered to change cooling air going to the oil cooler. BUT ALMOST AIRCRAFT MONITOR Cylinder head temperatures and EGT. That is how they can increase the oil temperature and know that nothing is wrong with the CHTs. Lastly, they typically run at 70% to 75% of power (WOT). That is around 2100 for a 2800 rpm rated motor.

However, we run blind of CHT and on some rigs are continually at 80% to 85% WOT when running around. That is producing higher CHT and we don't know what they are doing.

A friend of mine is a pilot that puts between 700 and 1000 hours a year on a twin with 2- TIO-360s. Those CHT stick to around 350 degrees with oil around 170. I know they have had at least two sets of engines hit TBO (time before overhaul) and changed out. But the oil typically sits around the bottom of the official recommendation. That makes me feel ok with temperatures at 160.

And like Larry said, we might be measuring at different places. Those hoses and oil lines can drop a few degrees as well. So you have to answer where the probe is first.

Lastly without CHTs, if you are running 180 - 200 you might not have to much flexability with CHT temperatures as you might be on the top end of the range. Start hammering on the throttle and without that extra cooling from oil at 160s, you might peak maximum CHTs. I have seen what can happen and it anit pretty. When a Cylinder top separates from the base, that is scarer sounding.

Most of the boats I know around here (all 540s) run about the same as yours. I do know an old airgator hull that sits around 150 and that engine is old as well but still running. That Kline runs about 160 with angle cylinders, but she has been as high as 185 when running hard. I always figured that just changing oil at 30 hours would do the job since she nevers sit long.
 
BF - The guage is new, but I can't be positive about it's accuracy. What's the best way to test it?

Larry - Yeah, I seen that comment. No doubt the h2ad had some serious probems when they first came out. Those problems were supposedly fixed in 1980 according to the H2AD Story (scroll down about 2/3 of the page):

"The final fix is the so-called "T" mod,
which was incorporated in all 1980 and later engines during
production as well as being a field retrofit. This mod improves
top end lubrication and involves even larger tappets."

Mine has the "T" stamped into the case, so it should have the fixes in place.....but Teresa knows that I HAVE TO run it once a week to keep the cam from wearing out. :wink:

The sending unit is in the same housing as both oil cooler lines, but I can't really tell which way the oil is flowing. I do have a small leak there so I've been planning on taking it apart anyway. I'd be able to tell then for sure.

Thanks pirate - I see that they like 170-180 range and not the 180-200 range that I mentioned.

marshmaster pat":3ivcr19p said:
Lastly without CHTs, if you are running 180 - 200 you might not have to much flexability with CHT temperatures as you might be on the top end of the range. Start hammering on the throttle and without that extra cooling from oil at 160s, you might peak maximum CHTs.
Click to expand...
marshmaster - Thanks for that consideration. You'd think I'd have thought about that since I had problems with cylinder heat in my previous angle valve motors. There's nothing worse than getting half way across the pasture and start losing power when the cylinders get hot.

All this condensation thinking started a couple of weeks ago when we took my cousin's h2ad on it's maiden voyage. He has a clear breather hose that comes up about 6" then has a small dip in it before following the side of the cage to the back of the boat. We were amazed at the amount of water that collected there in a normal day of running.
 
Hey Rick,
We always try and turn down the breather hose as close to the fitting as possible. That way when the moisture vents out of the case, and condenses on the cooler hose material, it will run down and out, instead of running back down into the engine if the hose goes up for too long a distance. Seems like the hose material does not cunduct heat very far from the fitting on the crankcase, and the steam will turn to water, and run back into water, and run right back down into the engine. This process can be repeated over time, and the crankcase get wetter and wetter.

I'm not sure how high you breather hose is raised up before turning down, but that could be a part of the problem. If it's too tall, you'll never dry it out.

Just a thought.

BTW, I like clear tygon breather hose too, then you can see the moisture removal proccess to make sure it's happening.
 
I have a 150 angle valve lycoming and the temperature never gets above 135 degrees, I have replaced the temperature gauge and questioned many people about the low operating temp. They all tell me that I need to be around 165 degrees for normal operating temp or change my oil every 10 hrs. I am also going to try and tape off the cooler a little bit, $3 a quart sucks...
 
Here's an old trick:

As soon as practical after the vent hose leaves the engine fitting, tie the vent line in a loose single loop (12-15" dia.) .... clear neoprene works best because you can see into it, and it's cheap to replace ... and then run the tail of it where you wish. The loop prevents flow-back to the engine.

Then, the first time condensation forms in it, it will show you the lowest point in the loop. That's where the water will accumulate. Heat the tip of a nail or awl and melt a small hole (1/16th or so) in the bottom of the tube at that lowest point.

The water will drip out when it accumulates, and the vent tube will still do it's job.

BF
 
I had a very in depth conversation with Jr. Jurnigan on this same issue when I had some issues with my motor and after I blew the first one up.(Rod bolt broke. Not a pretty site when you can look in the case and see parts). He guaged my motor for CHT's and noted how hot it was. (in the 550 range). To make a long story short I have always been under the impression that the cooler the better. I have a shroud on my boat and my oil temp never gets above 140. When I got the motor rebuit by Jr. and put in new guages from Diamondback. I thought the guage was bad. I called Diamondback and Jr. and they both said with a big oil cooler that was normal.
 
I'm breaking in my 0540. The average temp. this summer was about 140. I talked to Jr. last week & he said to cover the oil cooler to get the temp. up to about 180 to break it in. My vent hose goes up from the engine & then down the cage to the transom & has ss mesh wire on the end to keep out those pesty mud dobbers.

Oh yeah, what do ya'll torque your plugs to. I think Lyc. suggests 35 ft lbs, but I just can't get the nerve to go that much. ??? :shock: :idea: :?: :roll:
 
I just use the ole tighten till it feels good and then just a bump. Don't have a problem with leakage, so I guess its worked for me.
 
Truck drivers I know like to keep it above the temp water evaprates at. They say 220-250 Temps is what they want to evaporate comdensation and fuel in the oil.
 
While I wouldn't really want oil temps over 220, if you are on the cooler side and you changed your Oil at 50 hrs or at your discression sooner, shouldn't be a problem. I just don't like it when you get that milkey skum on the oil filler cap. If it's there, it's everywhere :twisted: You can put cardboard over your cooler to figure out temps. Then if you want to raise oil temps the cheapest fix is to put an alominum plate covering your old, to big oil cooler.
 
I currently have a 10 foot Gililieo with a Lycoming O-290-D. I have an oil temp and cht to monitor my temps. If I run it hard I would get CHTs over 450 and I would just back down to keep it in limits. I need a larger oil cooler. I've flown airplanes since the 70's and I've built and rebuilt my own planes. In the airplane group we like to see the oil temp around 180. 200 is too high, but you need 180 to burn off the moisture that developes in your engine. That white scum coming out of the breather is that moisture mixed with a little bit of oil. Your engine will last much longer is you have oil in the crankcase instead of water. It's good to keep the cylinders as cool as possible but the engine needs to burn off that moisture. Oh, where can I get a larger oil cooler?
 
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