Oil temp control

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FJLG
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Oil temp control

Post by FJLG »

I am in the process of purchasing a maule and I live in Saskatchewan and enjoy ski flying so I was wondering if there was a mod to control oil temp in the winter. A gate valve of some sort. It is a M7 260. Any suggestions would be appreciated
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andy
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Re: Oil temp control

Post by andy »

No official mods. A few owners have installed field approvals like cowl flaps. Most of us just block off 1/2 - 2/3 of the oil cooler inlet screen with foil tape. It's not an ideal solution when temperatures vary above and below freezing every day but the rest of the time it works pretty well. Having a long arm helps so you don't have to remove the top cowling.
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Re: Oil temp control

Post by flyusn99 »

I have a 1976 M-5-235 with a J1A5D (O-540) and have a field approval for just what you're asking about. We moved my oil cooler to the rear of the engine (like on your 260) with a NACA duct on the right side of my lower cowling that has a scat tube feeding into a funnel shroud over the oil cooler with a butterfly valve that has a push-pull control in the cockpit. It works marvelously! I can control the amount of airflow over the oil cooler from inside the cockpit. During start (and almost all winter) the butterfly is full closed. I can get my oil temp up into the 180 degree range even when temps are in the teens.

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Re: Oil temp control

Post by andy »

I thought about the same kind of field approval as flyusn99 except that I would use an adjustable iris diaphragm that might be less sensitive to wind pressure.
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Re: Oil temp control

Post by Hale-Yes »

Andy, I love that iris diaphragm valve, obviously that one is made for photography, do you know of one that is more manically robust, and would hold up the the vibration and air pressure requirements of an aircraft?
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Re: Oil temp control

Post by andy »

I haven't done a lot of research on the iris but this one is pretty rugged: https://ebay.us/eebgHc . The prices on these are all over the map. This one's reasonable. The trick with this is to figure out a way to mount it inside a section of duct. I thought two 3" flanges on either side of it with 8 bolts to hold the two flanges together with the iris in the middle would work: https://www.aircraftspruce.com/catalog/ ... langes.php. This one already has a hole in the adjuster lever to attach a control cable into the cockpit. The outer diameter is 12 cm which is larger than the 4" (10.61 cm) outer diameter of the flanges so attaching the flanges to the iris would be tricky. You can't drill holes in the body of the iris without messing it up. You'd have to construct a rectangular frame out of aluminum angle strips that would hold the whole thing together.
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montana maule
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Re: Oil temp control

Post by montana maule »

Check out the oil cooler shutter at https://antisplataero.com/products. I have pictures if I could figure how to post them. The file is too big to put on here.

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Re: Oil temp control

Post by andy »

Is the EZ Cool Cowl Flap for $369 what you are referring to, Montana Maule? I know there's at least one owner who has installed something like this. This approach involves more cost and effort since it requires a cowling modification. It has the advantage of regulating CHTs as well as indirectly regulating oil temperature. The oil cooler shutter or iris approach only affects oil temp since it doesn't affect air flow around the cylinder cooling fins.

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Re: Oil temp control

Post by Hale-Yes »

My cooling (and heating) problems in the low desert are a bit different than what you fellows require up in the cool country. I am looking for additional engine cooling, along with the ability to keep the oil at normal operating temperature when I do encounter cold weather.
The oil cooler design on the 540 235hp is one where air from plenum above the engine is bled off at the rear port side via two short sections of scat hose that run to a manifold and through the oil cooler, the other hose directs plenum air at the outside of the cooler, in what could be described as a questionable attempt to make a poor design work better. My primary problem with this design, is that it robs a lot of air from the plenum, right over the cylinder that usually runs the hottest. This lost plenum air would other wise would be used for cylinder cooling.
The 540 260hp system is a much better design. It utilizes a NACA duct in the port side cowling to bring air to a 30.77% larger oil cooler, a Niagra 20006A, 13 rows, verses the Niagra 20003A, 9 rows used for the 235hp. This does a much better job of cooling the oil and it leaves all the air in the plenum for cylinder cooling, a win, win. Several Maule owners have adopted this design on to there 540 235hp engines with a field approval, some have added a cockpit adjustable air valve in front of the oil cooler to regulate the oil temperature for faster warm ups, and warmer oil temperatures when they do encounter cold ambient air. IMHO this should be standard equipment on all 540's.
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Re: Oil temp control

Post by DavZeeMXT »

What would be a good oil temp for winter operations?
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Re: Oil temp control

Post by Hale-Yes »

Just from a what's best for your engine prospective, I would like to see oil temperatures in the engine at 180 degrees F. At this temperature your heating up the water vapor that is constantly being made by combustion enough to vent it off. Other wise it can combine with your oil to form acidic sludge and the water vapor will rust your expensive engine bits.
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Andy Young
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Re: Oil temp control

Post by Andy Young »

This one involves a modification of the stock oil cooler duct. It retains the stock oil cooler location, fits under the cowling, and uses a cockpit control knob and cable to open and close a restrictor door. Note that even when fully closed, the door does not block 100% of the air to the cooler. Air pressure on the door requires the use of a locking-type knob control (push button in the middle to release).

I hear what you’re saying about loss of air pressure for cylinder cooling with that oil cooler location. I rarely see cylinder temps over 325°, and often they are more like 290°, so not a concern for me.

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Re: Oil temp control

Post by andy »

The ideal solution might be a combination of cowl flaps and oil cooler air valve control. Cowl flaps will definitely help control air flow over the cylinders, raising both CHT and oil temperature in cold weather. If that doesn't warm the oil up enough in cold weather, then an oil cooler air valve would warm it up further. In hot weather the cowl flaps and oil cooler air valves would be wide open. If the rear cylinder ran hotter because of air being sucked away by the oil cooler air valve, then you would have an independent control to close off the oil cooler air without affecting the other CHTs.

Neither of these approaches would lower CHT temperatures in hot weather. Only additional air flow over the cylinders would do that. If I could pick only one mod that would work in both hot and cold weather, then I would modify the cowling to pull in more air over the cylinders and add cowl flaps to the bottom.
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Re: Oil temp control

Post by Hale-Yes »

Andy, In your situation, cold weather, I agree. For me its about improving the ability to remove heat from the engine. By going to the 260hp design, I would accomplish that in two ways, First, I would leave more air above the engine in the plenum available for cylinder cooling. Second, I would pull outside air via a NACA duct into a substantially larger oil cooler. By adding the ability of throttling the air with a valve before going through the cooler via a cockpit control, I can keep the oil temp in the operating range in cold weather.
Controllable cowl vents would allow the same to be done for the whole engine and also help prevent shock cooling when descending as an added bonus. The problem as I see it, is that this is just one more thing for a pilot to remember to do during his busiest time, landing. While I am dreaming. I would sure like to have the cowl vents automated with a manual over ride. :D :D
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Re: Oil temp control

Post by onfinal »

Hi Hale... can I follow up your remarks on the oil cooling system on the 260hp engines.

This sounds like a superior method of both oil and engine cooling. I would be very interested in any photos and drawings you or others might have available. Also any details of field approval paperwork.
My flying in UK and Europe see temperature ranges from, -5C (23F) winter night flying, to around 35-40C (95-104F) during summer trips into Southern Europe.
Being able to control oil temperature by varying the amount of air to the cooler would be of great benefit. Also using a dedicated scoop which does not divert air from within the plenum will improve no.6 cylinder cooling on the hot days.
Cowl flaps are great but it strikes me as the 260hp engine solution exists, the cowl alterations and associated plumbing should be Factory documented and thus reasonably straight forward to carry out on a 235hp.
The Maule owners who adopted this design, did they have the blessing of the Maule Factory, or better still, was it a Factory produced mod?
Perhaps a question for Duane?
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