From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Engine performance regarding cold starts, crankcase dilution, and vaporizer tests.
| Identifier | ExFiles\Box 50\3\ Scan170 | |
| Date | 27th August 1921 | |
| Oyl - G 27.8.21 Sheet #3. (4) After 1000 miles of running in which an exceptionally large number of cold starts have been made (to try out the pilot jet and induction pipe) the piston heads are dry and clean, except for a small accumulation of soft powdery carbon, quite different from the wet piston heads and hard black "enamel" which occurs on standard cars. (5) Crankcase dilution was 1% in 100 miles with this pipe, during which time seven starts were made from cold, with the pilot jet, and the car was run under ordinary touring conditions in cool weather (air temperatures 50°F.{Mr Friese} to 70°F.{Mr Friese}). Crankcase dilutions are deceptive things at the best, but a figure of 1% in 100 miles, under the above conditions, strikes us as very good. The pilot jet helps in keeping down crankcase dilution because of making a more certain start, but we have been surprised at the amount of gasoline collected in our bottles during the warming up period. Naturally our collections when warming up will be much greater than yours, because of our heavier fuel. For example, with an air temperature of 60°F.{Mr Friese} we collect 8 cubic inches of fuel from all six cylinders in 8 minutes idle running, the motor being started without the use of the primer or pilot jet and the water temperature rising during this period from 80°F.{Mr Friese} to 150°F.{Mr Friese} Considering that this fuel in the standard induction pipe is fed into cool cylinders in an irregular manner (as proved by the irregular firing of the engine when warming up with the standard pipe) and considering further that our test was taken at Summer temperatures, the cause of excessive crankcase dilution and carbonizing in winter is evident. Also the effectiveness of the induction pipe draining arrangement is illustrated. (The above test was taken with the drains as shown on XA-1096, but with bottles instead of the boilers.) As compared with the heated throttle, which allows the period of starting and warming up (which is the greatest cause of crankcase dilution) to pass before it warms up sufficiently to vaporize the fuel, the vaporizer scheme has obvious advantages. Also the vaporizer causes an increase in power, as compared with the standard pipe with 1" through-pipe, whether the latter is heated or not. This we have proved by dynamometer tests. I am shortly sending you photographs of the experimental device from which you will see that the appearance is not unsightly. In production it could be made much neater (and the tappets, etc. more accessible) by tucking away the vertical drain pipes behind the exhaust down-takes. | ||