ice cold carb throat/venturi

jaycoop · Jul 13, 2019

Just completed a rebuild on a ZAU - my first MM project and what a cool engine design. As I ran it for the first time, I noticed the ice cold passage between the carb and manifold. This may be normal?, but I have never experienced this. Is it due to the extended length of the throat?

old · Jul 13, 2019

Happens on all carbs on all engines. As gas is atomized in the carb it causes things to cool off a lot and is just how a carb should work. That is why many of the cars and truck had an air intake tube going to the exhaust manifold to pull warm air into the air intake.

jaycoop · Jul 14, 2019

Thanks for the explanation!!

rustred · Jul 14, 2019

the name for that is called the "venturi effect". the air is speeded up going through the venturi or restriction and cools off and thus creates less pressure, like a vacuum and causes the gas to be sucked out of the float bowl and drawn into the intake.

Bob · Jul 14, 2019

The evaporation of the gasoline adds to the cooling effect.

"Latent heat of vaporization".

jaycoop · Jul 14, 2019

Thanks for all the replies on this...I'm learning. I wonder too if the long connector between carb and manifold may add to this effect. I see why MM added this connector....even with this extension, the carb fuel inlet is not much below the gas tank outlet. The way the tractor is designed, there is no way to provide a gradual gravity drop between tank and carb. If anything, the line rises a bit as it comes over top of the hydraulic tank. I bet the designers struggled a little with this....

ice cold carb throat/venturi

jaycoop

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old

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rustred

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Bob

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