Cabin heater coolant diagram

[Birdseyeview]

Lots of interesting debate in this thread on air flow through the cabin heat exchanger but has anyone every determined by temp measurements if the cabin heat exchanger itself is actually getting enough coolant flow through it to get it good and hot?

My cabin heater kit is the one sold by Kitfox with the coolant flow tee'd off the main radiator hoses and with the two computer fans. However, it just doesn't seem to send out much heat into the cabin when it's 30-40 F ambient or colder (in Northern Illinois). In contrast my Toyota's heater will drive me out if I let it go.

Although the two computer fans do seem to push some air through it that I can feel, its not exactly a hurricane and its just not very warm. I've sealed up air leaks around the firewall and elsewhere to minimize cool ambient air ingress into the cabin but I'm wondering - Is there a way to modify the coolant plumbing somehow to potentially push more coolant flow through this cabin heater to get it hot without negatively impacting the coolant flow to the cylinder heads? The following diagram crudely depicts my current plumbing:

Scan 5.jpg

My CHT seems to always hover around 180 F so it seems that my cylinder heads are getting plenty of coolant flow. Or do I need a coolant thermostat or something else to raise the overall coolant operating temp?

Does anyone have the standard Kitfox set up that proves its output is more than adequate? If so what do you attribute it to? Any thoughts are appreciated.

[avidflyer]

I have a therm-bob thermostat on my 912 Kitfox 4 to keep coolant temps up in the winter. The bypass line goes through the heater core, and I get real good heat from it, till the thermostat opens and the coolant doesn't flow as well through the heater core. On my next Kitfox, I'm going to use a small radiator with 1" lines going through it for the heater core, so all the coolant goes through the heater core hot. The bypass line will attach after the heater core. The radiator I'm using is off a Yamaha snowmobile that had a phaser engine in it. Has a nice fan on it already. Another solution for my current Kitfox would be to put a valve in the 1" line after the heater core hose, so I could force more coolant through the heater core. That would require me to monitor the CHT temp a bit more of course. I do fly in northern Mn, so I deal with much colder temps than a lot of guys though. JImChuk

[AvDES LLC]

Lots of interesting debate in this thread on air flow through the cabin heat exchanger but has anyone every determined by temp measurements if the cabin heat exchanger itself is actually getting enough coolant flow through it to get it good and hot?

My cabin heater kit is the one sold by Kitfox with the coolant flow tee'd off the main radiator hoses and with the two computer fans. However, it just doesn't seem to send out much heat into the cabin when it's 30-40 F ambient or colder (in Northern Illinois). In contrast my Toyota's heater will drive me out if I let it go.

Although the two computer fans do seem to push some air through it that I can feel, its not exactly a hurricane and its just not very warm. I've sealed up air leaks around the firewall and elsewhere to minimize cool ambient air ingress into the cabin but I'm wondering - Is there a way to modify the coolant plumbing somehow to potentially push more coolant flow through this cabin heater to get it hot without negatively impacting the coolant flow to the cylinder heads? The following diagram crudely depicts my current plumbing:

Scan 5.jpg

My CHT seems to always hover around 180 F so it seems that my cylinder heads are getting plenty of coolant flow. Or do I need a coolant thermostat or something else to raise the overall coolant operating temp?

Does anyone have the standard Kitfox set up that proves its output is more than adequate? If so what do you attribute it to? Any thoughts are appreciated.

this is EXACTLY why I pulled the fans and went with ducted air. Yes those fans move air, but not much. And with the cabin as poorly sealed as it is, they were pushing enough air to keep anything but the tips of my big toes warm. That issue solved itself with the ducted air, however it took the development of a shroud and mounting etc etc.

I also just have standard y fittings on the main coolant lines. No thermo bob so no ability to comment there.

[Birdseyeview]

[QUOTE=AvDES LLC;107021]this is EXACTLY why I pulled the fans and went with ducted air. Yes those fans move air, but not much. And with the cabin as poorly sealed as it is, they were pushing enough air to keep anything but the tips of my big toes warm. That issue solved itself with the ducted air, however it took the development of a shroud and mounting etc etc.


I may have missed some of the discussion history here so please excuse me if you've already explained this in another post. Have you been flying with this set up to prove that it provides plenty of heat into the cabin? Does it ever provide too much heat? If so, how do you plan to regulate the flow to shut it off during the summer?

[AvDES LLC]

i have just crossed the 100hr threshold with this setup in my plane and it provides plenty of heat to keep myself and my lady warm in the Reno winters. It does get a bit toasty in the spring / summer months and to solve that I simply put a ball valve on the inlet line. When it’s hot out, close the ball valve and zero coolant flow takes place through the exchanger.

[bbs428]

I weighed a new 8" rad. fan I was thinking of using. It blows a lot of air but it's 1lb 13oz. Plus the amp draw. Ouch!

I think I'm warming up to your shroud. Weight would be miniscule compared to the bigger, stronger fan plus the savings in amps.
I might be able to bend up some aluminum sheet but not sure if it would look as good. I don't have much in the way of sheet metal tools/benders/brakes.
My heater core is 8"x 8" so I'd have to make my own variation. Now would be the time to do it!

Is that 3" hose from the firewall to the shroud?

Thanks for posting - really got me thinking in a different tangent.

[AvDES LLC]

Glad it got you thinking outside the normal box. These engines don’t have much for electrical output and sucking some up with a big fan isn’t always the best idea in my
mind. If you want to aim more for the “certified” approach, you can run a small 2 inch duct to a muffler shroud and have the outlet to that shroud go into a through bulkhead ducting port and into the shroud on your cabin heat heater.

drop me a pm if you want to discuss shrouds and whatnot. I can steer you in the direction of a possible solution to your dilemma.