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CRAZY COMBUSTION

A LOOK AT OLD-TIME WAYS TO LIGHT THE FIRE

Part 1

The Hvid combustion chamber illustrated at the moment of ignition. The pre-combustion chamber, called the fuel cup (A), projected into the combustion chamber. It had an array of oriices with a shallow well just below them. At the top of the fuel cup was an intake valve-actuated fuel valve (B) connecting to the fuel system. On the intake stroke, both the intake and fuel valves were open, letting fuel gravity feed into the fuel cup, aided by a small amount of piston suction. Fuel low was regulated by a tunable metering pin (C). Engine heat helped vaporize the fuel in the cup, and heat of compression ignited the fuel. The pressure and lame front pushed out through the fuel cup oriices, further mixing and igniting the remaining fuel, creating about 680 psi iring pressure and making the power stroke. The exhaust stroke is perfectly normal, and the cycle began anew.
The Cummins Engine Company was one of the Hvid licensees. Clessie Cummins put blood, sweat and tears into making them better. Cummins built and sold Hvid engines under its own name, including vertical marine engines, but most of its production went to Sears, Roebuck & Company, which sold them under the Thermoil name. This is a 1920 Cummins/Hvid with a 5-inch bore and a 7-inch stroke, making 6 hp at 540 rpm. Approximately 100 to 125 like it were made. All of the Cummins-built Thermoils for Sears were smaller—1½ and 3 hp— engines.
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Diesel World June 2019, OUR BEST ISSUE YET, Triple Turbo : It's the Perfect Truck, Save Yourself $15K, CP4 Failures Explained, Vintage Diesel With Spark Plugs, And More....