Etydhv

I couldn't find enough information on the internet for this topic. What I found can be paraphrased as:

Carburetor means easy engine start while fuel injected means manual fuel start up and carburetors are cheaper.

So how do carbureted planes compare against the fuel injected ones for GA purposes especially in long distance cold high altitude flights?

I looked for the M-9 Series and the specs doesn't reveal much.

Carbureted engines make use of a carburetor to mix fuel and intake air prior to administrating the airflow to the engine intake manifold. Fuel injected engines make use of a fuel metering unit which directly injects fuel into each cylinder of the engine.

Advantages to carbureted engines:

• Simpler


• Easier to start than fuel injected engines, especially when hot.

Disadvantages of carbureted engines:

• Carburetors use Bernoulli principle to draw fuel into Venturi, resulting in a temperature drop, which can result in carburetor icing.


• Less uniform control of fuel air mixture entering cylinders.

Disadvantages of fuel injection:

You need to do a business case. It's possibly not worth the price. The Bendix fuel injection system used on the Lyc is a fairly crude (by car standards) mechanical constant flow system, and the specific fuel consumption is perhaps 5-10% lower, maybe, at best, .4 lb/hp/hr vs .44 or so for a carb (cars are in the high .3s, diesels in the low .3s). Lets be generous and say the fuel burn is 9 gal/hr instead of 10. At 100 hrs a year that's a $500-550 saving. If you spend 5000 extra for the injected engine, it's 10 years just to break even. Hopefully the fuel injected option is a lot cheaper than that, or you do enough flying to recoup the extra price much faster.

You prime by pressurizing the system with the fuel pump (using the mixture) to inject fuel pretty much where the primer would be on a carbureted engine; so far so good, but it's a somewhat more finicky procedure and easy to flood.

There's a little bit of a pucker factor issue because you have a high pressure fuel distribution system snaking around the engine (yes there are primer lines on a carb engine but they aren't pressurized) so there is a higher fire risk due to a fuel leak (it's the main reason carbureted engines are always updraft - nobody puts the carb on top).

When the engine is hot and sitting on hot day, you can get vapor lock in the distribution manifold and lines, sizzling away like a pan of bacon in the plenum of the cowling, making the engine really hard to start. If you're on floats drifting away from a dock after pushing off and frantically trying to start the dang thing before you drift into the rocks, it becomes a big deal.

My personal opinion is the fuel burn reduction is not worth the costs, extra failure modes, and loss of simplicity and I prefer carburetors, for simple, low speed airplanes at least.

Performance wise, both types perform similarly at high altitude. Without turbocharging/turbonormalizing, neither will have enough air at altitude to create the same horsepower they can make at low altitude. Basic chemistry/physics there.