Cowl Flaps - cruise open?

[M20E-1964]

The person I bought my M20 from said that he flys cross countries with the cowl flaps open for better cooling.  What do other M20 owners think?  What kind of speed I provement can you expect with them closed?

 

 

[Bolter]

This is for my J-model, but I don't like the noise of the cowl flaps when opened (full or trail position) at cruise speeds.  If I can keep cool with them closed and adding more fuel or going a little leaner (depending on conditions), that is what I do.   I figure that if I can hear the air hitting them open cowls, that they are probably being stressed.  

The speed impact is a secondary concern as I am still reveling in the massive speed increase over what I used to rent.  

[scottfromiowa]

A knot or two, but there is a placard on the cowl flap control for speed max open.  If you have a multi-probe temp system you will be able to see that you are fine with them closed in cruise.  If it's not then you have a baffling or engine management issue.

[OR75]

I would think that at cruise and level flight, I would enrich mixture or throttle back if I saw the oil temperature was getting too high. very rare when that is needed (low oil level and very hot outside)

[danb35]

What Scott said--and if you don't have a multiprobe engine monitor, install one.  You shouldn't need to cruise with the flaps open--if you're running too hot, lean more.  Well LOP keeps things nice and cool.

[Piloto]

Quote: gmcd

The person I bought my M20 from said that he flys cross countries with the cowl flaps open for better cooling.  What do other M20 owners think?  What kind of speed I provement can you expect with them closed?

 

 

[John Pleisse]

Put them in "trail" for the same results. Remember, trail or full open will affect your heater shroud and interior heating in in the winter.

[Newmooneyguy]

My oil temp always runs high for some reason, CHT's are always OK.  I just crack open the cowl flaps and it makes a big difference.

[Mooneyjet]

In my short flying hours with m20C I keep the cowl doors close and I find my cht to stay cool about 300 running 75 rop but then I'm up in Canada where still fairly cool temperatures. 

[Bolter]

Quote: scottfromiowa

A knot or two, but there is a placard on the cowl flap control for speed max open.  If you have a multi-probe temp system you will be able to see that you are fine with them closed in cruise.  If it's not then you have a baffling or engine management issue.

[Lood]

Speed limit with cowl flaps open for my F is 150mph.

[Becca]

Quote: gmcd

The person I bought my M20 from said that he flys cross countries with the cowl flaps open for better cooling.  What do other M20 owners think?  What kind of speed I provement can you expect with them closed?

 

 

[M20E-1964]

I just flew x-country for about 5 hours.... with the cown flaps closed temps were fine. Open, closed, whatever, oil temp is always a bit on the high side of the green arc. Cylinder Head temp is always mid of the green arc.

So far, I havent seen any adverse affects of closing them.