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My "Huffer" - Getting Rid of Excess Heat

HFS

Well Known Member
Here is a picture of my "Huffer" - a blower system designed to evacuate hot stagnating air left in the plenum after shutdown.

I live in a very dry and hot climate, and it is not unusual to have hanger temps well above the century mark in the summer time. I wanted to be able to get rid of any stagnating air above the cylinders after shutdown, to facilitate overall increased cooling of the engine bay during that period.

When plugged in (right after shutdown), it's amazing how much hot air comes out of the exit area of the cowling. Even though I can only put in ambient temperature air, even when that air is 100* or more, it still acts as a heat sink for the stagnated air in the plenum which can reach over 200* after shutdown.

I have a mechanical timer on the power side, so it becomes a "set it and forget it" kind of system. Been using it (in some form) for 30 years + now, my cowling(s) still look to be in pretty good shape from a paint quality standpoint.

Just another point on the compass.

YMMV - And probably will!

HFS

Sorry about the orientation of the pic - maybe someone can help me with that also?
 

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Rotated the image. I just open the oil door, but where I live it's not too hot.

“Huffer”.jpg
 
Somehow innovation take over. I really like your though process. Now take it to the next level. Build one that is light weight and built in. Able to take it wherever you go and you will have a product that every Fuel injection airplane wants. I think you can do it.
 
Just me

I think i would try blowing air in one side of inlet, and let it come out the other inlet. Unless one has a baffle on top the engine along the split line, this should work well without having to blow air down thru the exit
 
Blowing Air Out The Exit

Instead of just evacuating the air under the plenum - I'm trying to "sweep" all heated/stagnated air in the cowling/plenum area after shut down. I want to have the air exit via the lower cowling opening, to net as much cooling as possible.

Also opening the oil door, on my airplane does nothing, because the plenum traps all radiated heat from the top of the engine - and the oil door is above the plenum, ergo - no help.

HFS
 
If your fan unit had a heat setting, it could work for pre heat too. You could have a separate heating unit you switch in the winter. Great design.
 
A solar powered marine ventilator along with a 90 degree elbow fab'd to fit the front cowl inlet would speed up the cool down. They move 700 to 900 cu. ft./ hour of air so a typical engine compartment would have more than 1 air change every minute.
 

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Hot air after shutdown

That is a great system you figured out David. I don’t have a plenum on my -8 but after tucking the airplane in the hangar after flying I put a small fan under the lower cowl exhaust opening and leave the oil door open (learned that from John Murphy). It’s amazing how much hot air comes out the front intakes and the oil door. When I’m on the ramp I just leave the oil door open after shutdown. I don’t have a spring on my oil door so I just use a length of stiff hose slit down the middle and slide it around the edge of the door and the edge of the opening in the upper cowl.

Oh- and yes I “know a guy” that forgot to close his oil door before start and had to shutdown to get out & close the oil door much to the delight and laughter of others on the ramp.
 
I don’t have a plenum on my -8 but after tucking the airplane in the hangar after flying I put a small fan under the lower cowl exhaust opening and leave the oil door open (learned that from John Murphy). It’s amazing how much hot air comes out the front intakes and the oil door. When I’m on the ramp I just leave the oil door open after shutdown.

This is what I do. I put it on a step stool, and I have it on a timer to run for an hour. I’ve attached a pic of the blower I use. It really does move a lot of air.

E56C3598-F7E0-4F53-AB9D-1554B453C7CD.jpeg
 
Here is a picture of my "Huffer" - a blower system designed to evacuate hot stagnating air left in the plenum after shutdown.
Great design! And I agree, you need to apply positive pressure in your plenum so you can effectively evacuate the hot air. You did well. Also agree that if you add heating elements, folks in colder climates can use it to pre-heat.
Quick question - I see you have a Sam James cowl on your RV7/8. I've got the same arrangement. What do you do to keep CHT's low on climb out...? Mine gets to 430 way quick if I don't keep the nose down and speed up. In cruise it settles at around 385.
 
I've seen folks at Oshkosh taxi in and shutdown and make a bee line to get their cowl oil door open to get the heat out as soon as possible. this is important if you have an electronic ignition. I don't have an electronic ignition but I still do it because any soak back heat you can remove from the accessories extends the life of those.
 
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