Diesel and Other Internal-Combustion Engines


| September/October 1996

  • Charter-Mietz Oil engine
    Fig. 25, Charter-Mietz low-pressure oil engine, 6 to 18 HP, courtesy of Charter Engine Company, Sterling, Illinois.
    Charter Engine Company
  • Mietz and Weiss oil engine
    Fig. 24, Longitudinal section of Mietz and Weiss oil engine

  • Charter-Mietz Oil engine
  • Mietz and Weiss oil engine

The following is a chapter reprinted from the book Internal Combustion Engines, published by the American Technical Society, Chicago, Illinois, 1937. Sent to us by Walter A. Taubeneck, 11801 52nd Dr. NE, Marysville, Washington 98271-6225.

Classification. An oil engine may be defined as an internal-combustion engine that uses oil for fuel, the oil being sprayed into the cylinder or combustion chamber, during or at the end of the compression stroke. Oil engines are of three distinct types the low-pressure, moderate-pressure, and the Diesel (high-pressure).

The low-pressure type of oil engine is so named because the compression pressure is only 50 to 160 pounds per square inch. Fuel is generally injected against hot plates, into a hot bulb, or into an uncooled vaporizer chamber during the compression stroke. When the atomized fuel comes in contact with the hot surface, vaporization occurs, and as the oil is usually kept out of the cylinder, only the expanding gases come in contact with the piston and cylinder walls. Initial vaporization is often produced by externally heating the chamber and after starting the engine the surfaces retain enough heat from explosion to be continuously effective as a vaporizer. These engines operate on the Otto cycle and the explosion pressures are not high, seldom exceeding 250 pounds per square inch.

Moderate-pressure oil engines employ compression pressures of 200 to 350 pounds per square inch. These engines may be designed to operate on cycles approximating the Otto or Diesel cycle. Ignition in this type is usually secured by methods similar to those employed in low-pressure oil engines. Injection cannot occur during the compression stroke as in the low-pressure type, on account of probable premature ignition. The temperature corresponding to 250 pounds per square inch pressure is sufficient to ignite most fuel oils, but this temperature is not high enough to insure perfect ignition at every stroke. To avoid occasional pre-ignition, the fuel oil in moderate-pressure oil engines is injected at the end of compression.

Low-pressure Oil Engines. The low-pressure oil engine operates on the Otto cycle and is so named because the compression pressure is low, seldom exceeding 100 pounds per square inch. In this type fuel is generally sprayed into the combustion chamber during the compression stroke. Ignition is usually secured by a hot bulb or a hot tube; the hot bulb being heated before starting the engine, the bulb retaining its heat from explosion to explosion. The pressures resulting from the explosion are not high, hardly as high as are found in some gas engines. Combustion is not as complete as in the higher-pressure engines, and the efficiency is correspondingly lower.

The Mietz and Weiss two-cycle low-pressure oil engine is shown in Figs. 24 and 25. The stationary engine is manufactured in single and two-cylinder horizontal units, while the vertical type is made in one, two, three and four-cylinder units. The horsepowers range from 2 to 400; the two-horsepower units operate at 600 rpm and the 400-horse-power units at 180 rpm.


Gas Engine Magazine A_M 16Gas Engine Magazine is your best source for tractor and stationary gas engine information.  Subscribe and connect with more than 23,000 other gas engine collectors and build your knowledge, share your passion and search for parts, in the publication written by and for gas engine enthusiasts! Gas Engine Magazine brings you: restoration stories, company histories, and technical advice. Plus our Flywheel Forum column helps answer your engine inquiries!

Be sure to take advantage of the Square Deal Subscription Program.

  • No Missed Issues.

  • No Renewal Notices.

  • No Additional Cost.

The Square Deal Subscription Program is designed as a paperless transaction with automatic renewals at a preferred low rate.   With advanced electronic notification, a 100% satisfaction guarantee and an easy opt-out plan, the Square Deal Subscription Program is the best value, risk free, eco-friendliest way to subscribe.

Facebook YouTube