Cooling air side outlets

[Area 51%]

Ryan, Where do you have your CHT probes mounted? My engine seems to be running hotter than expected at 25hrs, but I'm wondering if it might only SEEM to be running warm because my probes are under the spark plugs and not screwed to the cooling fins as suggested by Sonex.

Mine are installed per the Aerovee installation in this PDF:

http://www.aeroconversions.com/support/ ... nstall.pdf

They're about 1/4" outside the cutout for the top spark plugs, at either the 2 o'clock (pictured) or 10 o'clock position depending on forward/aft cylinder spark plug. The hole is into the meat of the cylinder head, not into a fin.

I have a cylinder head that came off the factory Xenos. The probe's screw hole is centered over the outermost head stud and an inch above the stud's center. I guess they have a "do as I say, not as I do" policy. The current owner reported very low CHTs.

Shoot me your email and I'll send you a picture.

[estegen@outlook.com]

Hi Kai , I have added the Sonex B vents to the side of the cowling as well as increasing the exit underneath . I can now clime to 3000 ft with CHT just under 400 deg F , This made the most difference from all the adjustments . Also the fuel burps are no longer an issue , using mogas 98 . Here are some pictures .

[pappas]

I am really curious about your top-mounted NACA ducts. Are they positioned to deliver air to the high-pressure area above the cylinders inside the aerovee baffles? The images look like they are dumping air behind the baffles.
I have been considering putting in a NACA duct like this over my #3 Aerovee turbo cylinder which is my hottest by 50 deg f, my hottest.

Was wondering if it might work. I have already added 2 vents on the underside of my B cowl. That did seem to help some but I am in Phoenix and it is summer now so I would like to be able to stay under 400 deg f during climb at 80-90 mph.

[Kai]

Hi Kai , I have added the Sonex B vents to the side of the cowling as well as increasing the exit underneath . I can now clime to 3000 ft with CHT just under 400 deg F , This made the most difference from all the adjustments . Also the fuel burps are no longer an issue , using mogas 98 . Here are some pictures .

Thanks!

Very interesting.

I was worried the side outlets could draw air from the bottom ones: Sonex Tech also pointed out that this could be an issue but emphasized that they had run no tests.

My cowling now sports the side inlets as well. Airtest scheduled shortly.

Kai

[estegen@outlook.com]

The naca ducts supply air to the rear of the engine , the aim was to cool the fuel system because I had burps using mogas 98 . Because the bottom opening still exists as well as the side B vents this did not effect the negative pressure required to cool the engine . I tried one modification at a time , the biggest difference was adding the side vents .

[pappas]

Thanks for the info!

[Kai]

The naca ducts supply air to the rear of the engine , the aim was to cool the fuel system because I had burps using mogas 98 . Because the bottom opening still exists as well as the side B vents this did not effect the negative pressure required to cool the engine . I tried one modification at a time , the biggest difference was adding the side vents .

That’s nice to know- what a relief!

My scheduled cooling test suddenly came much closer.

Thanks
Kai

[Scott Todd]

Its almost always about more exit area. I look at so many experimental airplanes and tell them this yet they are always hesitant to do so. Everyone is worried about speed. Many people are convinced 150% not counting the muffle, exhaust, vent lines, etc is enough. NOT!

[Kai]

Agreed!

No argument.

The short story is that #0525 had the factory standard bottom outlets and worrysome cht’s. After a bit of thought, some inquiries, and advice on these pages, I bit the bullet and installed the side outlets/scoops as well.

Result: the cht’s no longer keep me out of my beauty sleep.

As you said: it’s always about outlet area.

Thanks
Kai

[sonex1084]

I just installed the B model side vents on my Legacy cowl and love them!! Originally I expanded the bottom exit as suggested by other builders but still wasn't happy with the results. I flew the first flight with the side vents installed today and the results were immediately noticeable on climb out. I have an AreoVee 2.1 with 30 hours on the engine and 16 hours on new cylinders. Here are the results of the flight just prior to installing the side vents and the flight today. I flew at the same altitude, fuel flow and RPM for both flights. The only variable was the OAT. It was 68 degrees before the change and 58 degrees after the addition of the vents. CHTs before the side vents: #1 378, #2 371, #3 364, #4 328. After adding the side vents: #1 349, #2 356, # 3 335, #4 322. It appears the vents greatly improved the cooling of the back two cylinders. I flew the last flight with the original bottom vent open. My next flight I will close the bottom and report those results. I'm glad I added the side vents.