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).
Exhaust system explosions when coasting downhill and potential remedies.
| Identifier | ExFiles\Box 47\5\ Scan187 | |
| Date | 7th August 1928 | |
| - 2 - BY7/G.7.8.28. above. It must not be overlooked that the exhaust system is hot, and has heated up the weak mixture pushed slowly through into it from the slightly open throttle in readiness for the inevitable explosion which must take place when a flame from the exhaust port reaches it. Mr. Royce has had this question of firing in the exhaust system when going down hills even when the throttle is fully closed, before him for many years, but so far we have never succeeded in eliminating it. If a customer will drive with the throttle closed the number of explosions is low and the explosion itself small, but even under these ideal conditions the faults still occur, so that it can readily be understood that if a customer insists on keeping his throttle slightly open he is bound to be in trouble unless an excessively rich mixture is resorted to to prevent it. The reason why when we sent a carburetter set with a very rich mixture to Mr. Colville his complaint was not cured is that it is not possible for us to set a Rolls Royce carburetter to supply a mixture as rich as can be arrived at with some of the other carburetters on the market. The smell of the unburnt petrol is of course under such conditions extremely objectionable and the remedy in my opinion is far worse than the disease, as it results in partial gasing of the driver and passengers and sometimes sickness. There is one other way of dealing with the matter which whilst it would not eliminate the factor complained of would certainly reduce it considerably viz. the provision of a governor controlled throttle in which the mechanism worked on ball bearings. Under these conditions if the car was run with the governor control set for slow running the governor would close the throttle at all speeds higher than the one at which the engine was set to run, in fact you would arrive at a similar condition of affairs as that which already exists on the Phantom but it must be remembered that even the Phantom is not ideal in this direction. This, however, is a matter for WW. who are already over-burdened. BY. {R.W. Bailey - Chief Engineer} | ||