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Old 12-06-2017, 08:13 AM
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Tom Vaught Tom Vaught is offline
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Even though this discussion is about Holley Carburetors I will add on the Minimal Choke Discussion a link I had from my files concerning Rochester 2G and 2GC carburetors as it is well written and agrees with comments I have made in the past about condensation of fuel on the intake runner walls. The info, I am sure, came from Rochester Products Engineers.

http://www.carbkitsource.com/carbs/t...buretion9.html

"PURPOSE

The purpose of the choke system is to provide an extremely rich fuel mixture for cold engine starting and operation. This rich mixture is required because fuel vapor has a tendency to condense into droplets of raw gasoline upon coming into contact with the cold wall of the intake manifold. This action seriously robs the amount of fuel which normally would reach the engine cylinders to be ignited and burned.

You undoubtedly have noticed that if you place a glass of water in a room how moisture will immediately begin to form on the outside of the glass. This is condensation being formed by the warm air coming into contact with the cool surface of the glass causing beads or droplets of water to be condensed from the moisture in the air collecting on the glass. This same process takes place inside a cold engine."

That being said, I have also posted that when you do a quick "Tip-In" fuel is pulled from the walls, mixes with the increased air coming into the intake manifold, and any additional fuel then tries to replace the fuel on the wals of the intake so you get a lean spot (hesitation) in the engine.
The Accelerator Pump adds extra fuel to replace the fuel removed from the walls and still have the mixture be slightly rich.

So some say it does not work that way. All I can say is why do you need 4 Accelerator pumps on a Tunnel Ram intake with a large plenum volume if the situation mentioned above did not apply.

I also verified this process a few years ago on dyno testing (with EFI) and a camera in the intake manifold plenum. Physics did not change, be it a carb system or a EFI System. Fuel still attaches to the plenum walls even on EFI cars. Physics does not change.

So look at the link on Rochester carbs and Choke Function as it is a good bit of info. Different parts (Holley Vs Rochester) but the RP Engineers had it covered.

Tom V.

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