RV-8 heating system

Hi guys, my RV8 heating system doesn?t work properly, at 8000 feet, the incoming air is absolutely cold. I take the fresh air from the forward intake of the engine, and the heater is placed in the forward cylinder exhaust pipe. Any suggestinos?

Pablo Fernandez
RV8
Rojas, BA, Argentina

A couple of things

There are a few things you can do, that are typically done to try to increase the heat in the flow to the cabin.

First, you can restrict the amount of flow -- you probably have a 2" sceet tube going from the intake to the heat muff and then to the cabin. At the intake, try restricting the amount of flow -- I have a disc with a 1" hole over the intake, so that cuts the flow to 1/4 what it would be with a full 2" tube.

Second, to improve the heat conduction off the exhaust pipe and into the air, fill the heat muff with some stainless steel wool, or what we in the USA call a "chore-boy" -- it is a small bundle of stainless steel braided wire used to clean pots and pans in the kitchen.

Let us know how it works out.

It would help if your input tube was coming off the rear baffle (warm air) instead of the cold air that you are getting from the front ramp (if I am reading your post correctly).

My 8 has a custom exhaust system (think C172 style) with a muffler and I can melt my leg even when the OAT is -20 to -30 C when running at cruise power.

The AWI exhaust system I have has studs spot welded in the area where the heat muff goes. I get a huge amount of heat into the cabin on my -8 and I think those studs are the reason. They significantly increase the surface area the air flows over so more heat gets transferred. I also think it causes the air to be very turbulent and have to take some bends before exiting the muff. In the conventional application without the studs I think a lot of the air never gets even close to the exhaust pipe.

Ken, Steve, thanks for your advices. I will try it and then let you know.
Thanks again

vansrv8 said:

It would help if your input tube was coming off the rear baffle (warm air) instead of the cold air that you are getting from the front ramp (if I am reading your post correctly).

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It is safer to take the air from the front ramp, however, to minimize risk of exhaust gases getting into the cabin in the event of an exhaust leak.

The rear baffle is probably 'OK' because the flow is down through the engine and should carry exhaust out the cowl exit, but what about while taxi-ing? Not enough airflow to resist the natural convection that would carry exhaust up through the engine into the upper plenum.

And besides, it is not very much warmer than the outside air.