Summer temperatures and cooling

[13brv3]

Do you have a manifold pressure gauge, or at least an option to connect a MAP sensor to your engine monitor? If so, that makes a dandy cowl pressure sensor.

[Bryan Cotton]

Do you have a manifold pressure gauge, or at least an option to connect a MAP sensor to your engine monitor? If so, that makes a dandy cowl pressure sensor.

I don't. I do have some old Motorola pressure sensors and a raspberry pi, but I'm not sure I have the ambition.

[13brv3]

I bought one of these a while back to try to measure differential pressure, but I've had that same ambition problem. I also just don't have a good way to run the hoses through temporarily.
https://www.amazon.com/gp/product/B099ZYCV1L

[Bryan Cotton]

Rusty, run your lines out an air vent and then up through the cowl outlet or inlet. Just use the good duct tape. That's out of the Sikorsky flight test playbook.

So in the name of science, I taped over both oil cooler plenum exits inside and out. Left the plenum cover off and went flying.

Screenshot_20230620-210641-363.png (576.39 KiB) Viewed 7880 times

Screenshot_20230620-210657-554.png (638.69 KiB) Viewed 7880 times

Last Sunday we stabilized at 219-221 F in cruise. Tonight after 12 minutes of flight, including a climb to 2500' it was 226 and slowly rising. We did a simulated engine failure as we stayed right over the airport.

So I'm calling that one a fail. Onto the next science experiment. Stand by.

[Bryan Cotton]

I mounted a little piece of pipe into my exit plenum and secured it for a test flight. The idea is to pull the air out to a separate external exit.

air goes in here.png (549.41 KiB) Viewed 7793 times

air comes out here.png (509.95 KiB) Viewed 7793 times

This aluminum tube is sealed to the plenum with metal tape. I used a little shop vac hose for a temporary test.

hose through bottom of cowl.png (709.7 KiB) Viewed 7793 times

I even used the hose end that plugs into the vac as my exit.

shop vac pipe.png (511.83 KiB) Viewed 7793 times

Initially it seemed like I had a winner. Temps looked really good during climb. They were slowly going up towards 200, it was 90F out, and I was at full power and 80kts. Leveled off and after a bit it seemed the rate of increase was going up even though I was at cruise power and 100kts. So I landed, and found the hose had softened, rested on the exhaust pipe, melted and sealed itself.

Based on my initial positive results I am pursuing this further. The shop vac hose, besides not handling the temperature, is only about 1" ID and corrugated. It was too long also. So I've got some 1.75" scat tubing on the way. I plan to do this right and try again.

Why am I messing with this approach? My CHTs are almost always under 300F. I don't want to screw that up. The only time I went over 400 was a month ago, doing patterns in the heat. The oil got hot first.

[Bryan Cotton]

Ok, getting serious about this mod. I'm no longer baffled on what to do.

baffled no more.png (582.94 KiB) Viewed 7734 times

[Bryan Cotton]

I've got the rivets drilled out of my baffle. It's all apart on the bench. I used it to make a paper pattern. The black outline is where the opening currently is. The green outline is how far I can go if I ignore the rivet line.

pattern clecoed.png (677.63 KiB) Viewed 7668 times

Here I have marked out where my 1.75" tube needs to go.

pattern for locating pipe.png (562.55 KiB) Viewed 7668 times

[Bryan Cotton]

Here is a progress update. Tubes riveted onto the baffle:

tubes riveted to baffles.png (647.23 KiB) Viewed 7479 times

Baffle back together and clecoed to the case:

baffle with tubes in place.png (601.25 KiB) Viewed 7479 times

This is a mockup reverse scoop. It's a box constructed in two pieces. The flanges go corner to corner and will mount inside the cowl with the ramp sticking out.

mockup reverse scoop.png (698.57 KiB) Viewed 7479 times

I am going to try one hose and outlet first, and record results. Effectively I'm just increasing outlet area by about 2.5" per scoop.

Come wintertime, I see cabin heat experiments in my future.

[Bryan Cotton]

Two reverse scoops.

two reverse scoops.png (638.01 KiB) Viewed 7366 times

[Bryan Cotton]

I still need to trim the hole before I can rivet it in.

outside view reverse scoop.png (500.02 KiB) Viewed 7341 times

inside view reverse scoop.png (507.74 KiB) Viewed 7341 times