Continued lowering in the grade of fuel obtainable compels automotive engineers to produce engines that will utilize it with maximum economy. The manufacture of Pacific coast engine-distillate with an initial-distillation point of about 240 and an end-point of 480 deg. fahr. was abandoned by the principal oil companies early in 1920. Utilizing this fuel efficiently through its period of declining values forced advance solution of some fuel problems prior to a general lowering of grade of all automotive fuels. Keeping prominent certain essential features of economical design in connection with carburetion, the problems have been:
  1. (1)
    An absolutely correct metering for all engine speeds and throttle positions so that the proportion of air to fuel meets correct engine design
  2. (2)
    Adaptation to changed engine design, especially in connection with the manifold, or the entire mixture path; even fuel distribution to all cylinders being of higher importance than limiting manifold depression, and cylinders not pulling together having caused the largest loss in many designs
Realizing that the lower the grade of fuel the more difficult even distribution becomes and the more disastrous the results from poor distribution, the best way to accomplish maximum economy and power is stated as being the provision of a carbureter producing a mixture meeting theoretical operating conditions under throttle control with economy and flexibility, and designing manifolds that permit use of this mixture by insuring even distribution to all cylinders. A carbureter used for the past five years is illustrated and described in detail, with supplementary performance charts, and a fuel converter is likewise discussed. Manifold designs are next illustrated and commented upon, the conclusion being reached that in some cases a compromise between manifold depression and manifold turbulence on the one hand, and compression on the other, has made possible the use of extremely low-grade fuel and increased the power output to some extent.


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