COMBUSTION-CHAMBER DEPOSITS—A RADIOTRACER STUDY

AN IMPORTANT effect of combustion-chamber deposits is their tendency to raise the engine's need for higher octane fuels; also, they may cause uncontrolled ignition of the fuel-air mixture and misfiring of spark plugs. This paper describes a new approach to this problem.

By means of radioactive hydrocarbons, present in tracer amounts, the authors have been able to conclude the following about the effect of gasoline hydrocarbon composition on deposit formation in the combustion chamber:

1. 1.
   The deposit-forming tendency of hydrocarbons goes up strongly with increasing boiling point.
2. 2.
   Aromatics are considerably worse deposit formers than paraffins. Olefins are intermediate.
3. 3.
   The carbonaceous part of combustion-chamber deposits appears to form via a mechanism involving condensation followed by carbonization.
4. 4.
   Careful control of the back-end is needed to make a clean-burning gasoline.