X-Mozilla-Keys:                                                                                 
Mike Wills wrote:

At 08:26 AM 11/10/1999 -0800, you wrote:

Ken Powell wrote:
  When the thermostat opens and the radiator starts doing its

thing (cooling), the engine suddenly starts injesting heated air and the
already rich mixture (remember, high power requires a rich mixture) becomes
richer still; since 2-strokes are very sensitive to mixture this extra rich
mixture absolutely kills power.

Ken Powell

I always thought carbs mixed the amount of fuel consistent  with the
mass of the air flowing through the carb. Higher temperature air
lower mass so less fuel. Am I missing something?


Paul Lamar

Paul,

  If this were true why would there be a need for a mixture control on that
old Cessna, it would be self compensating wouldnt it? Ken's explanation is
consistent with what happens on the old Cessna during a runup when you pull
carb heat. Less air density due to the heated air and thus a richer mixture
and associated rpm drop. It makes sense to me anyway.

Mike Wills

Yep! I was wrong see the last message. The carb works on volume and not
mass.
I am too tuned in to modern mass airflow sensors.

Next time I pull the carb heat I will make a point of checking the EGT.
 
Paul Lamar
 
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