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).
The causes and testing of explosions in the silencer.
| Identifier | ExFiles\Box 38\4\ Scan034 | |
| Date | 1st June 1921 | |
| contd. -2- Hsl/LG1.6.21. positive cure for explosions in the silencer is to switch off both ignitions, but, of course, there is always the risk of the explosions taking place when they are switched on again. We have carried out the following tests in order to prove these results. If we take a standard car and coast down a long hill with the throttle shut we get two or three explosions in the silencer. If we take the same car, and at the top of the hill, run the engine dry of petrol so that the induction pipe is dry, and then turn on the petrol and if we like, flood the carburetter, we then ge run down the hill with the throttle shut, we get no explosions at all in the silencer. We repeated this test with a very fine adjustment on the throttle and we found that we had to have a very big leak past the throttle before a mixture is sucked up into the induction pipe and caused explosions in the silencer. Once, however, we had got a very bad leaking throttle, the explosions were practically continuous. We know there have been cases where, making the throttle a tighter fit, has reduced these explosions. We think it will be found that what happened in those cases was that the throttle leaked air which mixed with the petrol already in the pipe. The number of explosions, and the degree of them depends a lot under what condition the engine has been running before the throttle is shut, for instance, if we run full throttle low speeds, a condition which we know is bad for petrol collecting in the pipe, we then get the worst and most explosions. If, on the other hand, we run the engine with the throttle very little open and with a very weak mixture, which is the best contd:- | ||