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).
Analysis of engine overheating causes related to ignition, spark plug gaps, plug temperature, and compression ratios.
| Identifier | ExFiles\Box 34\2\ Scan103 | |
| Date | 5th May 1918 | |
| Contd. -2- EH/LG:5.5.18. ignition does not cause over-heating is because the charge burns so slowly. One can quite understand the charge burning slowly because there can be very little compression in the cylinder at the time of the spark as the inlet valve has only just closed. We found that if we increased the spark gap on the plug which was firing early from .014" to .050" it made a very big difference and with the .050" gap we could get over-heating due to early ignition. We found that with a sparking plug which was hot, although not hot enough to pre-ignite, we could more easily obtain the over-heating due to early ignition, on the other hand, with a very cool plug such as C.B. type K.L.G. it is very difficult. We attribute this to the fact that the hot plug does make the charge in a state quicker to ignite. We found that a hot plug will fire a weaker mixture than a cool one; the spark gaps the same in each case. We also made tests of running oil through the cylinder jackets instead of water. With this we could run the engine up to 150 to 175°C. We found that with the higher temperature we could easily cause pre-ignition. We also tried different compression ratios. WE found with the higher compression ratio we could more easily obtain the over-heating. We madecertain during these tests that we were getting our pre-ignitions electrically and not by over-heated plug. In the cylinder which was being observed, we | ||