Carburetor Types for K&B Engines

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Carburetor Types for K&B Engines

Postby Arctic Cat Rider » Thu May 14, 2009 6:24 am

Why are there different styles for carb location on the K&B engines?

All the airplane engines seem to have the carb located over the crankshaft up front, and the high performance ducted fans and inboards have the rear mounted rotor disc. Does the rotor disc provide more power??

DO rear rotor disc carbs have a low end adjustment??
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Postby K+B.91 » Fri May 15, 2009 5:42 am

To answer your question simply, the 'through the crankshaft' type of induction is very primitive and doesn't lend itself to high RPM efficiency.
The drum rotor is far more efficient than through the crankshaft, and the disc rotor is even more efficient again over the drum rotor.
The carbs on both my rotor/drum engines have low end adjustment, even the older style barrel carbs with the large interchangable venturi's.
The reason that all plane engines have through the crankshaft induction is because they don't rev like a ducted fan or marine engine, so they don't need the more efficient form of induction.
You will also notice that plane engines have somewhat smaller carbs than marine/ducted fan engines, because that's all they need.
Cheers.
K+B.91.
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Postby MECOA » Fri May 15, 2009 9:48 am

Crankshaft induction is not primitive, sub piston porting is.

The limatations on crankshaft induction is the timing, smoothness of the passage and size of the inductance hole. With a rear rotor you can can make a larger opening with a longer full open duration and more precise timing. Also you have a more direct path for the fuel flow.

All the induction designs have the same result. Some are just more efficient than others.

Actually the Zimmerman type rotary valve is the best so far.

Keep in mind this is a small portion of the engine design that may be coupled to a poor performing engine design. So everything must be designed as a whole.
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