O-540 Baffling

[Wes Ragle]

Guys,

Does anyone have some pics of a baffled O-540 they can share? In particular I would like to see how folks are handling the forward area that goes over the engine case. I am using Vans baffling and would like to see how others have modified it to work with the Bearhawk cowl.

Thanks,

Wes

[Blackrock]

Wes, this is how I did mine. Works well, but It stick with the Vans oil cooler location - I switched sides.

[Mark Goldberg]

Here is the only picture I could find of my front baffles Wes. Mark

[Wes Ragle]

Thanks Mike. Thanks Mark.

What I'm worried about (now) is the gaping hole between the supplied forward pieces and the nosebowl. It looks like Mark has custom sheet metal in that area. Mike's looks a lot like the supplied pieces. Seems like it would be relatively easy to "scab" on an extension to bring it closer to the nosebowl. Don't know.

Wes

[Battson]

Hi Wes,

This is what I did with mine:

https://photos.app.goo.gl/VoZiUkAfTQZTfbXt1

It works great - if anything my engine runs too cold... but that's a good thing, easy to save some cooling drag by reducing the outlet.

[swpilot3]

Hey Battson, I'm really interested in what you did with your baffling, but the pictures here aren't coming up. Are you able to repost them or fix the link? Thanks!!

[Battson]

I've shared a link for now. I need some time to figure out how to fix decades of broken Hyperlinks, after Photobucket went manic.

[Wes Ragle]

Hi Jonathan,

That looks awesome! Makes perfect sense.

Fuel injected, no extra louvers and whatnot on the cowling, and running on the cool side. That is hard to argue with. I'm going to try it.

I just watched "A look around our Bearhawk" on youtube again and was reminded that you have cowl flaps. I assume that if I go with a standard outlet with the lip that would be roughly equivalent to having the cowl flaps open all the time. Also, my engine is low compression built specifically for auto fuel. So, I should be able to run rich and fuel cool it during the early going without fouling plugs.

One other thing. I seem to remember that the RV cowlings came with an extra piece that attached to the top cowl half at the inlet to smooth the transition as air entered the plenum. Your baffling addresses that issue as well.

I hate high temps. Like you say, there are easy ways to make it run hotter if it runs too cool. Never easy answers if it starts out too hot.

Oil temps OK?

Thanks a Bunch,

Wes

[Battson]

My oil was much too cold to start with, so I moved it to a remote location the engine mount (firewall would have worked better, but I didn't have room) - this was a good move. You can see where I first mounted it in the picture - this was a bad idea. The weight caused several repeat cases of cracked baffles.

Now I have a short section of SCAT hose from the rear baffle to the cooler diffuser box, which restricts the flow a little. That brought my oil temps up nicely, in summer they are nice and hot, but not too hot, and in winter they are middle of the range. Cold oil is clearly a bad thing.

During winter, cruising lean of peak, I need to run closer to peak rather than leaner or else the CHTs drop into the yellow range (cold). Cowl flaps closed about 320*F.

I cruise with cowl flaps closed in all engine setting regimes, there's always enough airflow to keep the CHTs in the middle of my green range (about 355*F based on the conservative limits from Mike Busch - Savvy Aviator - this is like 120*F below the manufacturer's redline), so we are talking cool. During any extended cruise-descent I need more cowl flaps to close, the engine drops into the yellow cold range (below 280*F).

It's only at full rich climb that I need to open the cowl flaps full open. In summer that can push some temps into the 'yellow' hot warning range - again set conservatively - during at extended climb at 75kts from sea-level to 10,000ft sort of thing. Remembering my yellow starts more than 80*F below manufactures redline. But at that point, I lower the nose and climb at higher airspeeds to keep it in the green range.

From memory, my cowl outlet area is about 100 square inches with the flaps shut, and 120-130 square inches with them open.

[Battson]

Ooo - and the other thing - remember the cowl moves upwards in flight, because of the high pressure pocket you are creating atop the engine. This pressure, combined with the aerodynamic forces, push the cowl upward up to a 3/8 inch; at the nose bowl.

For that reason, it's important to leave at least a 3/8 inch; gap between the front of the baffle and the cowl inlet. The baffle material can easily bridge that gap.

[Wes Ragle]

I think I understand: Make sure the sheet metal ends 3/8 inch short of the inlet upper lip (front to back) to allow the lip to rise past the sheet metal.

Wes