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 devices, including a visible spark advance indicator and power charts.
| Identifier | ExFiles\Box 41\4\ Scan016 | |
| Date | 28th January 1930 guessed | |
| - 3 - not follow it except that the carburetter is set a little on the "lean" side. Cold starting conditions etc. are compensated automatically. Demonstration. As installed these two devices gave extraordinary results in lack of manual control, slow speed, pulling, steadiness of acceleration, and lack of detonation. The performance at very low speeds on steep grades was particularly noticeable, although the car is not fitted with a hot-spot. A visible spark advance indicator was fitted, and it was noticeable that as the speed increased above say 40 m.p.h., the ignition began to retard itself and would continue to do so as this speed was held, due to the increase in the internal temperature of the cylinders which made less advance necessary. Another interesting point is that "detonation" is impossible, as the very fact of the steep pressure rise after ignition causes the spark to retard itself. Power Charts. Mr. Stanton had a number of interesting power-charts on automobile and aircraft engines showing optimum spark advance obtained manually at full and partial throttles, and the degree to which this advance is reproduced by his device. In almost every case the advance curves were approximately as shown in the small chart in sketch showing that a droop in the advance is required for best results at high speeds because of the rise in internal engine temperature. Also the curve of optimum advance under road conditions was almost horizontal except for the droop at the ends. As he pointed out this advance can only be accurately obtained by allowing the engine to "read" the indicator diagram and adjust the spark to correspond. If you are interested in this device Mr. Stanton will assist in developing drawings and samples as required. Mr. Stanton stated that the real difficulty had been in developing reliable small poppet valves. In five years work he claims to have overcome this objection entirely, but gave no details. He promised to discuss this further if we were interested. Yours faithfully, ROLLS ROYCE OF AMERICA, INC | ||