A DISTINCTION is to be made between non-continuous-wear and continuous-wear measurements. To the former class belong measurements where the piston-rings are weighed or the cylinders and piston diameters are measured. Such a method takes a great deal of time, not only because of the long duration of the test itself but also because of the time necessary for the removal of the pistons, weighing, measuring, and re-assembling the engine.
In the latter method, cylinder wear is measured by determining the ash content of oil dripping from the piston while the engine is running. A standard fuel and lubricating oil is used, and wear is expressed as a “wear factor”-the ratio between the weight of ash collected on the sample used and the weight of ash collected from the standard sample. This factor correlates well with actual wear measurements.
Wear decreases with decreasing load, but increases again with very light loads within specified limits. Heavy fuels give slightly more wear than lighter fuels. Addition of 0.005 per cent of quartz dust into injection air multiplied the wear six times. Organic acids added to the fuel did not affect the wear. Tests with Diesel engines have proved that the temperature of the cooling water has little effect on wear. With the addition of 2 per cent or more of distilled water, wear is approximately doubled.