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).
Experiments with induction systems to overcome cold starting difficulties and the effects of temperature on detonation.
| Identifier | ExFiles\Box 66a\1\ scan0164 | |
| Date | 2nd February 1927 guessed | |
| contd :- -4- results, we have been unable to find a system which without the aid of quick heating overcame the cold starting difficulties. With low temperatures and the low volatility of the present day fuels the problem briefly resolves itself into metering practically liquid petrol to the different cyls. and with low u induction pipe velocities none of the systems we have tested give uniform and consistent distribution. Heat supplied by means of a 'hot spot' near the carb. is the only method we have found to give satisfactory results as in our std. exhaust heated system. This system we find possesses another advantage apart from the quick warming up enabling easy start with a cold engine and that is in regard to detonation. Careful experiments made in this direction both on the test bench and road, shew us that the temp. of the hot spot made no appreciable difference to detonation. On the other hand the cyl. jacket water temp. considerably influenced detonation, the engine became more prone to detonate as the temp. increased. This result is borne out on other cars and was noticeable on the Lorraine Dietrich. A test which was made on the bench with a std. Phantom of 5.2 to 1 compression ratio would take 23° ignition advance at 1250 r.p.m. full load without detonating when the average cyl. jacket temp. was 39°C but this had to be reduced to 17° advance to prevent detonation when the jacket temperature increased to 85°C. If the induction system is water heated it is necessary to keep the engine water temp. fairly high for good distribution and economy whereas with the contd :- | ||