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 effects and optimal placement of a 'hot spot' on an induction pipe to improve fuel distribution.
| Identifier | ExFiles\Box 75\2\ scan0225 | |
| Date | 26th May 1921 | |
| Contd. -3- Hsl/LG26.5.21. ------------ a paraffin blow-lamp. We have found this to be a wonderful help. By means of asbestos sheets etc. we can apply a hot spot on any part of the induction pipe, see the effect of it and apply it and take it off at will so that we could observe accurately the exact effect of it. For instance, we could have an engine firing at low speeds, it was missing fire and beltching out black smoke in some cylinders and popping in others due to weakness. If we applied the heat one could observe the gradual leveling up of the mixture until the engine was running evenly and maintaining steady torque. If we removed the heat it would go back to its original condition. In all our tests we have found that the best position for the hot spot is as close to the carburetter as possible. This appears to be a reasonable effect. The idea of a hot spot, as we see it, is to give us good distribution, for instance, with a single-cylinder engine, one would not imagine that any advantage would be gained by a hot spot. The hottest spot is certainly inside the cylinders - the problem on a multi-cylinder engine is to get an equal quantity of petrol into each cylinder. If we are, therefore, going to use a hot spot to improve our distribution we certainly should vaporize the petrol as soon as possible. It is certainly too late to do it on our engine after the petrol has divided at the "T" joint. If we vaporize the petrol earlier on we do not get any difficulty with variations in the induction pipes. If the hot spot cannot be above the carburetter then it should be somewhere on the pipe which crosses over the engine. We proved that the position in which we arranged the hot spot is contd:- | ||