Cabin heat solutions?

[takair]

I was thinking what Rich said regarding cowl flap effect.  Also, the heat muffs are a poor fit.  They leak around the edges and cowl flap open provide an additional path for the heat flowing through the muffler cavity.  
 

Regarding the OP question, one place to look at on any Mooney is the aft bulkhead wire harness transition.  If you open the aft equipment hatch, there is a large opening on the lower left of the bulkhead.  This is often poorly sealed, especially after work is done on the aircraft.  If the vacuum system was removed and the second pump came out, there can be an especially big opening.  For some reason, even a small opening here will suck the heat out of the cabin.  Once I sealed this and the wing roots, the plane is much more comfortable.  Take a look there, easy and cheap fix if you are leaking there.  

[PT20J]

I originally wrote the lack of heat off to additional cold airflow cooling the heat exchanger. But then @A64Pilot mentioned his heat had not just cool temps but low airflow with the cowl flaps open. This caused me to investigate further and I noticed that mine does the same thing. The amount of hot air coming out of the vent at the base of the console increases noticeably going from fully open to 1/2 open (electric cowl flaps). From 1/2 open to fully closed it is nearly the same -- lots of hot air.

I think the culprit its likely the location of the air inlet which is hidden behind the lip of the cowling opening. Higher airflows with the cowl flaps open apparently cause the air to bypass the inlet.

Skip

[Will.iam]

2 hours ago, PT20J said:

I originally wrote the lack of heat off to additional cold airflow cooling the heat exchanger. But then @A64Pilot mentioned his heat had not just cool temps but low airflow with the cowl flaps open. This caused me to investigate further and I noticed that mine does the same thing. The amount of hot air coming out of the vent at the base of the console increases noticeably going from fully open to 1/2 open (electric cowl flaps). From 1/2 open to fully closed it is nearly the same -- lots of hot air.

I think the culprit its likely the location of the air inlet which is hidden behind the lip of the cowling opening. Higher airflows with the cowl flaps open apparently cause the air to bypass the inlet.

Skip

You could be on to something there as my 252 has the air opening at the back top of the baffling wall and is routed by both left and right exhaust before coming into the cabin, i seem to have abundant amount of hot air at any Cowl flap setting

[hais]

19 hours ago, takair said:

I was thinking what Rich said regarding cowl flap effect.  Also, the heat muffs are a poor fit.  They leak around the edges and cowl flap open provide an additional path for the heat flowing through the muffler cavity.  
 

Regarding the OP question, one place to look at on any Mooney is the aft bulkhead wire harness transition.  If you open the aft equipment hatch, there is a large opening on the lower left of the bulkhead.  This is often poorly sealed, especially after work is done on the aircraft.  If the vacuum system was removed and the second pump came out, there can be an especially big opening.  For some reason, even a small opening here will suck the heat out of the cabin.  Once I sealed this and the wing roots, the plane is much more comfortable.  Take a look there, easy and cheap fix if you are leaking there.  

Thanks, will check this as well.

[larrynimmo]

On my J …down to 0 degree F my interior bakes when I fully open the heater vent

[hais]

Thank you all for the suggestions. So: largely the issue is operator error. 
Heat only comes from the Center - the knee and overhead vents blow cold air only.

I had the CHT today at about 320F, heat was coming in fine. However, not strong enough to cook the cabin if OAT is very low, so I will try @BorealOne’s solution  of plugging the vents. 
 

I checked the avionics bay as well, there’s no gap there that would sap hot air out - at least nothing big that I could observe. 
 

Has anyone ever tried to put an adapter at the Center vent to redirect hot air upwards? We will try to make one and give PIREP if it helps. 

[201er]

On 12/4/2021 at 1:26 AM, hais said:

Has anyone ever tried to put an adapter at the Center vent to redirect hot air upwards? We will try to make one and give PIREP if it helps. 

Yes, Mooney did.

Edited December 5, 2021 by 201er

[81X]

I’ll note that my 231 is terrible at producing cabin heat with the cowl flaps full open, just ok with the cowl flaps in “trail”, and will cook you out of the airplane (excluding your frozen toes) with cowl flaps closed with the heat lever full open.  I’ll also open the defroster valve to spread the heat around a little more when it’s really cold out.  Cowl flaps are the biggest variable in maximum heat output for me with ROP/LOP and lower power settings (descending) being contributing factors.

Ensuring the overhead and “knee” fresh air vents aren’t leaking substantially is also on my pre winter checklist.