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, focusing on the effects of piston ring fitment, gas leakage, and friction on horsepower.
| Identifier | ExFiles\Box 19\7\ Scan038 | |
| Date | 1st May 1917 | |
| Wor{Arthur Wormald - General Works Manager}/EH/L19515. 2. proportion to the speed of the engine and that a leakage that would appear tremendous when the engine was turned by hand would not make any appreciable difference in horse power at normal speeds. I realise that excess gas leaking past rings might create other faults, such as over-heating and burning off the oil, which would reduce the HP. In the case of our engines the difference in the fitting of the rings between a powerful engine and a medium one is something that we cannot feel or measure. I have also made tests by testing the HP with badly fitting rings and by removing all the rings except one,and by using different types and strength of rings. From the results of all these tests I have found that a good fitting piston and rings is far more essential to obtain even slow running than to obtain maximum power. When the engine is running slowly there is time for the air to leak past the piston, both on the compression stroke and the suction stroke. Time must be the most important factor as regards the amount of leakage. We get the maximum HP from an engine when we remove all the rings except one, so that we get the benefit of reduced friction. I do not want to create the impression that I am advocating poorly fitting rings, but the points I wish to emphasize are that the difference in HP on our cars is not caused by any variation in gas-tightness, piston and | ||