Rotax 912 carb heat

[adam.rigden]

Good morning.
I am in the process of completing a Kitfox series five with a rotax 80 hp.
In Canada carb heat is mandatory. Three options present themselves...electric...using waste heat from coolent or rotax's airbox.
I am leaning towards the electric option because of its compact size...I am told that it draws 6 amps and it may overload the stock alternator. Anyone out the use this method??
I dont think i have room for the airbox and i would have to modify my drip pans to fit the "hot water" option...not.to mention the extra piping required which would also add to the complexity of servicing the carbs....
Any comments/advice/help would be appreciated....

Thanks,
Adam (happy series 5 owner)

[jiott]

I personally would be very leery about adding that much electrical load, after witnessing and hearing about the Rotax Ducati regulator failures with am loads much over 13 amps. It is easy to reach this amp load if you have an EFIS, some nav/strobe lights, and a radio (adds 5-6 amps during transmit).

If I were to add carb heat, it would be the water coolant type; always on, no engine performance reduction, no electrical load, no exhaust heat muff. My impression from this forum is that is what most people are using if you need carb heat.

[Mcslamma]

Hi Adam,
Glad to hear of another Kitfox owner so close, I have a Model IV-1200 in Port Severn, 912ul with standard carb-heat system, ducted through airbox from exhaust manifold shroud, only thing I have done is added a screen at airbox, in case aluminum spacers separate as has happened to some, hence they would have ended up in the engine, causing damage., Cable operated, has been working great, not in the way, I am in Port Severn, on straight Floats, and skiis in winter..I would like to see your airplane sometime, I am up that way lots, for work, you are welcome to see my airplane anytime too..Craig

[Danzer1]

The std. internal alternator is "20 amp" but rated for 18 max and rated for 16 continuous load. Doesn't really matter if the carb heat is considered intermittent or continuous. What you need to know is: is the 16 exceeded with the other "have to have on" continuous loads on when the carb heat COULD also need to be on.

Another alternative (pun) would be to install a higher rated external alternator.

Add up your continuous loads - don't forget things like transponder, meters, gauges, lights and other things that run in the background that are easily missed. If it has a power connection, it has a load.

Greg

[Esser]

Before I modified my 914 to be fuel injected, I had planned on using a small heater like this one http://www.ultralightnews.ca/bing/carbheater.htm

However, I would set it up with a valve and not have it always on as it does indeed rob power. I think this would be your simplest option.

I also have an external alt. and it adds significant weight. I think 7lbs.

[TahoeTim]

off topic, but do you run a dual regulator or another method to connect both alternators?

[Av8r3400]

To the OP, my vote would be for the coolant heated type.

I'd agree that the electric unit would be too much for the standard charging system to handle...

[HighWing]

Just wondering. In the typical Kitfox 912UL installation, carb heat has never been an issue due to the induction location. If a system is mounted simply to comply with government regulations and likely to be never if ever used. Does it really matter what type is mounted? In my mind cost and effect on induction efficiency would be primary considerations. It seams that it's inclusion would be largely "cosmetic".

[RobS]

In my opinion, I think Lowell's thoughts are spot on. If Rotax 912's really don't (seldom, if ever) need carb heat, the electric system would be the easiest to go with. And if you ever did need it, I bet you'd be willing to turn down a fair amount of the other electrical load to make sure it performed properly. And, in a pinch, I know I'd be willing to kill a battery to ensure I got the bird on the ground safely.

[kitfox2009]

I have a 912UL on a Vixen. Installed the hot water manifold system about 5 years ago. Always on.Never had an icing problem. Disconnected the water tubes last year to see if there's a power difference.
No decernable change . Easy to install. I believe Bob at Light Engine sells them.
Cheers
Don