Linear actuators in engine compartment

[Nev]

Number 1 sometimes runs 100 degrees cooler than number 2 (that's a puzzle)

Terry, do you have the little "shield" baffle that partially blocks airflow right in front of Number 1 & 2 cylinders ? It helps to keep them warmer (or rather stops them being too much cooler than the others) due to being exposed directly to the incoming airflow.

Thanks for the feedback regarding the Antisplat cowl flaps.

[TrueAirSpeed]

Nev, I have a prominent air dam in front of number 1 and nothing in front of number 2.

[Bcone1381]

I wonder why the position of the louvers works. I see them placed here on many production aircraft. I now suppose if one measured static pressure every inch along a fuselage with static ports we would get the lowest pressure on the outside of the cowl where the air bends to conform with the fuselage (like we would expect on have the lowest pressure the top of a wing.)

Richard is using it..... Its also clean and I suspect low drag.

[whee]

Hey Whee, how/where did you install yours? Mine are in and running. Mechanically they're fine, but unfortunately I'm seeing very little effect on the CHT's. They do have a small effect on the oil temperature due to their location on the cowl cheeks ! I did a couple of flights with the manometer to double check, and at best there might be a 0.5" change in pressure differential, but only if I really try hard to see it. I'm wondering if it's due to the position of them interfering with the airflow through the lower outlet.

I'm getting a first class lesson the laws of unintended consequences, due to trying fix problems that don't exist

Mine look like they are installed in the same place as yours. That’s a low pressure zone on the cowl. Size appears similar. My mechanism isn’t as robust as yours so there less stuff in the air flow path.

My memory is a 20F CHT difference between cowl flaps open and closed. A quick look at my engine data shows something like 16F for one specific flight.

I did design my air cooling around the idea that belly outlets aren’t ideal, belly pods make it even worse and cooling drag can add measurable loss of speed. My tunnel outlet is really small and significantly blocked by an exhaust muffler. It takes pretty cool conditions to make it possible to cruise with my cowl flaps completely closed. But I can do unlimited touch and goes or unrestricted climbs with the cowl flaps open.

[whee]

Jono, No cowl lip on mine. That was a deliberate decision.

[Nev]

Incidentally, I flew mine both with and without the cowl lip to see the effect of the cowl flaps. Even without the exit lip there was no significant effect opening the cowl flaps.

[whee]

Nev, IDK why we see such starkly different results. Mine make such a big change that the volume of air I get out of my cabin heater changes when I open the cowl flaps. I’m guessing it’s because there is too much air coming into the cowl when the flaps are closed so the air spills back out the inlets and disrupts the flow into the cabin heating system.

[Nev]

Nev, IDK why we see such starkly different results. Mine make such a big change that the volume of air I get out of my cabin heater changes when I open the cowl flaps. I’m guessing it’s because there is too much air coming into the cowl when the flaps are closed so the air spills back out the inlets and disrupts the flow into the cabin heating system.

One area I might explore, is to "neck down" the main outlet area by the exhaust pipes. I can probably do this relatively easily for the sake of comparison, the idea would be to see if it then "forces" the air to use the cowl flaps by making that the preferred path. Currently the outlet tunnel are is 130 sq/inches which I gather should be on the larger end of the fleet scale. I deliberately sized it at that by incremental increases during the test flying, then once satisfied it was sufficient outlet area, fine tuned it with the lip size.

Whee, do you duct oil cooler air from the baffles ? I do, so that will be reducing the upper cowl pressure. This is an area I might also explore further.