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).
Misfiring at low speeds and the impact of spark plug gap size on slow running performance.
| Identifier | ExFiles\Box 178\4\ img011 | |
| Date | 5th April 1932 | |
| To H.{Arthur M. Hanbury - Head Complaints} From Hs.{Lord Ernest Hives - Chair} c. to __ By.{R.W. Bailey - Chief Engineer} c. to __ For. c. to FK. ORIGINAL CHASSIS BATTERY IGNITION. X6095 With reference to the attached. The mis-firing at low speeds has been difficult to locate. On the last 25 H.P. car which was run in France, part of the routine test every day was to make a definite test for this phenomenon. Very occasionally it would occur but then without touching anything it would disappear. We hope it will not be necessary for us to reduce the plug gaps to .19". This is a smaller gap than we have ever used on any of our cars, and it is smaller than any of the other makers use. The standard gap fixed by the plug makers as the best compromise to suit all cars is .25". With the smaller gap we shall definitely have less reliable slow running. At the present time the makers of cars with fluid flywheels are emphasising the advantage they have in phenomenal slow running on top gear. Although we cannot hope to approach them, it would be unfortunate if we had to sacrifice our present slow running quality. HS{Lord Ernest Hives - Chair}, | ||