Carb Options for Small Continentals

[MarkH]

I'm currently flying a club Remos with a Rotax while I shop for a taildragger (likely with a 65-100hp Conti) and as I fly the Remos, I find I really like the altitude compensating carburetor.

At minimum, living in the desert, I intend to add a mixture lever so I can lean for the Density Altitude. But, it leaves me wondering what other options exist to lean these engines other than add a mixture or leave the mixture wired full open.

Is there an altitude compensating carb available for small continentals? Is there one STCed for certificated planes?

 

[Dan Thomas]

Is there an altitude compensating carb available for small continentals? Is there one STCed for certificated planes?

Don't know of any. The TCDS for the airplane you buy will have the approved carbs listed on it, usually. If the airplane is old enough, it's likely to have a Stromberg (Bendix) carb, which is a really good little carb compared to the MS MA-3 carbs that are the more modern equivalent. There is provision for the mixture on those Strombergs but a lot just had a plate over the cavity and they ran full-rich all the time. The mixture control is a back-suction type that works in cruise but will not act as an idle cutoff for shutdown. I would still choose the Stromberg over the MA-3; I have flown them and find them far smoother than the MS carbs, which can be a maintenance pain as well.

Altitude-compensating carbs adjust for air pressure. They make no adjustment for temperature, so you're still adjusting mixture if you want best economy.

 

[flyingron]

The only altitude compensators I've seen are for bigger engines like the 435/480 lycomings. The PS5C pressure carb has this for an option. My Navion (unofficially) had one of these.

 

[tonycondon]

Stromberg Carb mixture control only effective above 5000 MSL. I was happy to get the mixture reinstalled on mine though, but I cruise the 120 at "high altitude" often.

 

[Dan Thomas]

Stromberg Carb mixture control only effective above 5000 MSL. I was happy to get the mixture reinstalled on mine though, but I cruise the 120 at "high altitude" often.

Mine worked at 2000 feet easily. For 20 years. But then, I had machined my own mixture control components for it (it was in a homebuilt) and it might have been more effective. The original used a series of tiny drilled holes in the upper valve plate; mine used a machined, ramped groove. It might have restricted the vent air more, and thereby been more effective.

From the overhaul manual:



Edit: That carb may also have had a bigger metering jet, too. It was on an A-65 but I seem to remember it being jetted for an A-75, but that was well over 40 years ago. If it had a bigger jet, that would explain why it leaned at lower altitudes. It was already delivering too much fuel for the A-65.

 

[tonycondon]

yea the cessna 120/140 manual says > 5000 MSL for the Stromberg. My experience has been that trying to lean below that brings an immediate reduction in power, so you end up back at full rich. Above that you end up at a lean position. About 9000 Feet I am *almost* to the full lean position in full throttle cruise. NOTE: THIS IS FOR THE STROMBERG CARBURETOR ON A C-85. THERE IS NO IDLE CUT OFF. changing the geometry of the plates would certainly change the behavior of the system

 

[GeorgeC]

I'm currently flying a club Remos with a Rotax while I shop for a taildragger (likely with a 65-100hp Conti) and as I fly the Remos, I find I really like the altitude compensating carburetor.

Why not just get a taildragger with a rotax? I've seen a couple A220s pop up for sale.

 

[MarkH]

Why not just get a taildragger with a rotax? I've seen a couple A220s pop up for sale.

That sounds as my initial plan, but my plans require a standard airworthiness certificate due to some reported issues flying in Mexico (according to Baja Bush pilots). And I have not found an option that offers a total in a taildragger that checks that box.

 

[Huckster79]

Very happy with my stromberg fueling my c-85 “stroker”. Don’t let folks tell you the mixture doesn’t work in them, as you will be told that. As Dan explained it works, just differently.