Thursday Trivia

Welcome to Thursday Trivia where we offer up a historical automotive trivia question and you try and solve it before seeing the answer after the jump. It’s like a history test, with cars! This week’s question: What year was the thermostatically-controlled automatic choke introduced, and by which maker? If you think you know the answer, don’t choke. Just make the jump and see if you’re right. The two components of the chemical reaction known as combustion are a fuel and an oxidant. In an internal combustion engine, the mechanism to create an efficient mix of those elements has evolved over time. Some of the earliest automotive engines used an atomizer, which a device that employed a rotating brush to pick up gas from a bowl and fling it into the air being pulled into the combustion chamber by the descending piston. Wick carburetors proved more effective than the atomizer and worked somewhat in the same fashion as a Zippo lighter or Coleman lantern. The float-type carb was the invention of Dr. Wilhelm Maybach – yes, that Maybach – and would prove a revolutionary leap in internal combustion engine induction, and one that would survive for decades. The basic function is remarkably simple: a gravity-fed fuel supply would fill a bowl in which there there had been fixed a float. The float would close a needle valve, shutting off the fuel supply when the bowl reached optimum capacity. Fuel would then be drawn out of the bowl through a port in a second housing that was the mixing chamber. The requirement that the fuel tank be above the carburetor, so as to allow gravity to do its work, meant that carbs were mounted low and were hence predominantly updraft style. It wasn’t until the 1920s with the introduction of the mechanical fuel pump, that gas tanks could be moved away from above the – typically hot – engine and pressure-fed carbs could use more efficient down-draft and side-draft formats. Still to be solved was the issue of an engine running smoothly when cold, when fuel doesn’t have the chance to effectively vaporize in the combustion chamber. In order to overcome this cold engine issue, a change in the fuel/air ratio is required, dumping in a far more rich mixture to help overcome the lack of total vaporization that occurs before the engine reaches operating temperature. This is facilitated predominantly by what is known as a choke, a mechanism that either constricts the air passage or increases the size of the fuel jet to increase the amount of fuel coming into the cylinders. You’ve probably seen plenty of cars with manual chokes, usually operated by a knob on the dash, or in the case of my 240Z, by a lever on the transmission tunnel. If you’ve ever driven a carbureted car or truck that didn’t have one of these manual knobs it most likely was because it had an automatic choke, which would save you the trouble of pulling it on and pushing it off to maximize the engine’s efficiency and drivability. I say most likely as some cars – like the Jaguar XKs of the fifties – used a solenoid-operated ‘tickler’ on one carb to add fuel for starting when cold. The automatic choke, like the automatic transmission, became a symbol of convenience and perceived luxury, and in fact, it was introduced on a brand that would go one to gain a reputation for being favored by those who appreciated just such conveniences and luxury, Oldsmobile. From The Old Motor:

1932 was the first year that Oldsmobile offered its new straight-eight along with the six, which had been the standard fare for quite some time. Even with the addition of the new power plant in one of the most trying years of the Great Depression, Oldsmobile’s sales dropped from forty-eight thousand in 1931 to a low point of only seventeen thousand for the year. In addition to the new 82-hp. 240-c.i. eight-cylinder engine, Oldsmobile featured the following new innovations: the Stromberg downdraft carburetor featured an automatic choke; a decarbonizer operated by dash-mounted plunger, injected a chemical into the intake manifold, which then entered into the cylinders when used just before engine shutdown.

Today, every gasoline-powered car and truck sold in America features computer-controlled fuel injection, a situation demanded by stringent fuel economy and emissions standards.  It’s getting to the point where in another generation or so automotive carburetors will be as foreign to enthusiasts as are today wooden wheels and crank starting. Image: The Old Motor