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).
Fuel sensitivity and engine knock tests conducted on a 3 1/2 Litre Bentley car at Brooklands.
| Identifier | ExFiles\Box 150\1\ scan0163 | |
| Date | 6th August 1936 | |
| R E P O R T. 6th August 1936. TESTS MADE AT BROOKLANDS 6/8/36 WITH MR. LEGH-JONES' 3 1/2 LITRE BENTLEY CAR - NO. BYH 32 - ENGINE NO. A3 BD{Mr Berend} The object of these tests was to check up on the fuel sensitivity of the engine and to ascertain, if possible, why detonation occurs on straight spirit of 70/71 O.N. although the engine is stated to have been designed to run on fuels of lower anti-knock rating. When the car was taken over at Shell-Mex House it was said to have Shell in the tank and the writer's impression whilst driving the car down to Brooklands was that a light knock was occasionally audible between 1750 and 2500 r.p.m. on full throttle with full spark advance, i.e. at road speeds of 35-50 m.p.h. It was not considered that the knock was offensive or harmful and it was completely eliminated by retarding the spark about one third on the manual control. The condition was similar to that of several other cars of the same type handled and agreed with what Mr. Hives, the Experimental Engineer at the Rolls Works at Derby, had said to the writer about a year ago. The programme carried out at Brooklands comprised:- 1. Weighing car and passengers. 2. Fitting Tapley Performance Meter temporarily in order to get some idea of power output and comparative performance on different fuels. 3. Checking speedometer for accuracy over measured half mile at 30, 60 and 90 m.p.h. 4. Making tests on Commercial, Shell and Ethyl for degree of knock, pull as recorded by Tapley Meter, and maximum speed over half mile, on plugs as installed in car (KLG 850) 5. Repeating tests under (4) on new set of KLG 850 plugs to check deterioration. 6. Final check on original plugs and fuel (Shell) as in car's tank when taken over. 1. WEIGHT Car empty 3783 lbs. 33.77 cwt. 1.688 tons Car with driver and passenger 4137 lbs. 36.93 cwt. 1.846 tons 2 & 3 SPEEDOMETER errors, taking mean of a number of observations, are:- Speedometer 30 m.p.h. - true speed 29.26 m.p.h. " 60 m.p.h. - " " 56.25 m.p.h. " 90 m.p.h. - " " 84 m.p.h. The instrument, therefore, read 3% to 6% fast over the range 30 - 90 m.p.h., which is considered fairly accurate. The above data were necessary in order to translate the Performance Meter readings into approximate H.P. figures. | ||