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Permalink Reply by Jay M. Johnson on March 15, 2026 at 6:44pm

I'm based in Wyoming and I;m sure it gets colder than Vancouver.

I installed an adjustable oil cooler damper that works well.  During the colder months, I put about an 1 1/2 inch wide metal tape, type used on home heat ducts, on both ends of the coolant radiator.  It still takes 10-15 minutes to warm up.  Climbing out, have to monitor the temp closely as the temp can soar...After the average daytime temps get above 50 degrees, I remove the tape.

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Permalink Reply by Matt Pope on March 16, 2026 at 11:05am

Hi Perry,

The engine in Roger's 701 is on the Rotax ring mount, and the oil cooler and muffler configurations are quite a bit different from yours. Air to the oil cooler comes from a NACA duct, and the damper is a simple butterfly valve in the duct in front of the cooler. The cabin heat comes from a muff around the muffler that always has ram air flowing into it, and flow from there into the cabin is controlled by a butterfly valve that's mounted in the firewall. Mine's the same as Roger's and I can send pictures if you want, but it's so different from your installation that I don't think it would be much help. 

I'm not sure what to suggest to get the oil temp up other than the options you've already looked at, but for cabin heat maybe something like Viking's system would work in your case (it routes engine coolant back through the firewall to a little radiator in the cabin). It does add several potential failure points to the cooling system though. 

Cheers

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Permalink Reply by Perry Delano on Thursday

Hi Jay and Matt,

Thanks for your thoughts on my inquiry. In the short term I will go for the tape. Matt if you have a picture of your cabin heat muff install, please send it to me. I have not seen much on heat muffs with Rotax Engines.

Longer term, I see the advantage of having the oil cooler near the firewall with the NACA vent and small length of duct: So easy to install a butterfly valve/damper and it seems apparent one does not need to have the oil cooler up front be blasted by the prop like I do. Food for thought there. 

Using the coolant to supply a cabin heater seems the way to go, I will check out the viking arrangement. I realize it is adding a point of failure, but using heat muff around exhaust has its concerns as well. That said, 701 is so drafty CO might not be a big concern.

Cold is not a big concern in Vancouver right now. Delta Heritage Airpark where my plane is based looks more like a lake at the moment. Great if 701 was on floats.

Perry

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Permalink Reply by Matt Pope on Thursday

Here's a picture of the shroud that fits around the muffler. It's held on by two long hose clamps, and the round opening you can see is where the scat hose attaches it to the butterfly valve in the firewall, which is controlled by a push-pull cable in the instrument panel. The lower edge that you can't see is open and faces forward, so it kind of scoops air in where it heats up around the muffler. 

I think I remember seeing your muffler under the cabin of your 701, so it might be easy for you to make something like this work through a vent in the floor.

A CO monitor is definitely a must have with a system like this, but then again I think a CO monitor should be required equipment in any case. 

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