ABC's of Carburetion



	CARBURETOR SYSTEMS Continued

		closed simply cuts down the air supply and raises the vacuum applied to the fuel outlets, so that more than usual fuel may be drawn into the cold engine. The manual choke is, of course, controlled by the driver; he can simply set it where the engine runs best as it starts and warms up. Automatic chokes are becoming more and more the accepted choking mechanism; in general, here's how they work: An automatic choke contains two opposing forces: thermostatic coil tension acts to close the choke valve and vacuum pull on the choke piston acts to open it. A cold coil will hold the choke closed against the vacuum pull. Warm air is brought to the choke coil through a heat tube open to fresh air near the exhaust manifold. As the coil is heated, it "relaxes" and allows the vacuum pull on the piston to open the choke valve and hold it there. By careful design and calibration, automatic chokes are made to furnish the correct choke action during the start and warm-up period.
	CHOKE SYSTEM The Choke System supplies the rich mixtures we saw were needed for the starting and warm-up of a cold engine. The choke valve when



	SUMMARY

	The upshot of it all is that the carburetor has to be an all-around star performer at the beck call of the automobile driver. With today's engine and fuels, the modern	carburetor is a far cry from its ancestors of just a few years back, but reduced to its basic functions, it still follows the fundamental principles of carburetion.

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