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).
Test report on a new pipe and vaporizer scheme, detailing issues with engine loading and liquid fuel collection.
| Identifier | ExFiles\Box 50\3\ Scan169 | |
| Date | 27th August 1921 | |
| Oyl - G 27.8.21 Sheet #2. We therefore made up a new pipe without 1" through-pipe and with the vaporizer scheme shown on XA-1096 attached. We have now run this pipe 1000 miles on the road and dynamometer and find that it is very difficult to load the engine up. We have been able to produce a slight tendency to miss after a long high-gear hill climb or a long pull on the level with the brakes on, but only by using an unduly strong mixture. With a properly regulated mixture it will not load. We attribute the slight remaining tendency to load to the 5/16" drain pipes being too small, and are replacing these with 1/2" drains throughout. It is possible that with the small pipes when the boilers are hot, the out-rushing gas from the first liquid which gets down may prevent the passage of further liquid down into the boilers. We have been interested in attempting to find the proportion of the liquid fuel, normally "slopped" into the cylinder, which is caught by the drains and conveyed to the boilers, but we do not know any direct means of finding this. At first sight it would appear that only a small proportion could be expected to find its way into the drains. But this is not so, as is proved by the amounts collected in a short time and by the observed effect in the running of the car. (1) For example, the boiler collecting from cylinders 4, 5 and 6 had 3 1/4 cubic inches of fuel in it after one normal start with pilot jet, and an idle run of 2 minutes, with water below 100°F.{Mr Friese} and air temperature about 65°F.{Mr Friese} (2) Again, after manoeuvring the car for 2 minutes on the pilot jet, two starts on pilot jet, and one idle run of 1 minute, with the accelerator depressed and engine making about 1000 r.p.m. (water and air temperatures as above), we collected ten cubic inches of gasoline from the same boiler. (3) Furthermore, one notable effect on the running of the car is that the accelerator can be held right down with the water scarcely warm, say 80°F.{Mr Friese}, immediately after starting on the pilot jet, without any irregularity of running. This is impossible with the standard pipe and American gasoline until the water is thoroughly warm, say 160°F.{Mr Friese}, which generally does not happen till the car has been running for 10 or 15 minutes. After such a period of warming up and before a steady running condition is obtained, our cars on these cool mornings often have liquid fuel dripping from the exhaust nozzle. | ||