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Michaels Web Site
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Date: 1-26-2020
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Number of Hours: 0.00
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Manual Reference:
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Brief Description: Cabin Heater Testing 2 of 2
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Photo 1: Scatt tubing reversed between top and bottom of muff.
Photo 2: Supply opening put back to being only partially open.
Photo 3: The reason a partially open firewall valve makes things COLDER is that the flapper valve is (in this photo) fully CLOSED, so no air gets in. When the valve is FULLY open the open valve lets in ONLY air from the scatt tubing; it blocks out any air from under the cowl. With the valve only PARTIALLY open it lets all the cold air from the lower cowl go directly into the cabin without being heated. Sonexes with a turbo setup may not have this issue since the turbo exhaust is in this general location and is very hot.
Tested today, 1/28/20:
- OAT on the ground was 37F. At 3,000' it was 32F.
- During taxi I measured 82F at the valve.
- On climb out, full power, measured 92F.
- At cruise, 2,900 rpm, 64F
CHTs: 240, 175, 255, 253.
OT: 161F
OAT temps were 10F colder than my first tests, and temps at the flapper valve today were correspondingly lower. Next I'm going to open up more holes in the exit baffle. I'm also going to try deflecting some of the cooling air going to the cylinders, since they run so cool in the winter. Maybe bringing up the CHTs will add a bit more heat.
Note: The flapper valve is the only place I can get some kind of quantifiable reading. I can't just measure the air temperature because it changes too much and takes too much time to make that change. But the valve is made of metal and soaks up the heat, and that's what the thermometer is reading. But I guarantee that is NOT the temperature of the air coming out the valve. So just because I measured 92F during climb does NOT mean I'm getting 92F air coming into the cabin. All you have to do is put your hand 6" from the valve and you can feel that the actual amount of heated air is not very warm at all. If I start to see 100F+ at the valve then I'll bet I'll feel a marked difference in the actual air temperature.
So the tempeature at the valve is giving me a "relative" reading rather than an "abso
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Swapped locations of the scaft tubing in the muff
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Put the inlet hole back to the previous partially blocked opening.
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This is why I think opening the valve only part way does not work.
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