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 testing of Dubilier spark suppressors on a Bentley test bed unit.
| Identifier | ExFiles\Box 168b\1\ img016 | |
| Date | 7th February 1938 | |
| DUBILIER SUPPRESSORS. Spark suppressors have been tested on a Bentley test bed unit to determine their effect on the performance and general running of the engine. Dubilier suppressors of 15,000 Ohms resistance were used. Power curves were run with and without suppressors using standard air and exhaust silencers and standard carburetter needles. KLG. P.L.B.30.X plugs were used set at .035". No difference in power was obtained. These curves were then repeated under the same conditions except that the air inlet temperature was raised to 40° Cent. by means of heater coils in the air silencer. This was done in order to reproduce car conditions as closely as possible. Under these conditions power output with suppressors was slightly less than without, but the loss was negligible being only 0.25%. The B.H.P.figures are given below. | R.P.M. | No Suppressors. | | Suppressors Fitted. | | |---|---:|---:|---:|---:| | | B.H.P. | B.M.E.P. | B.H.P. | B.M.E.P. | | 3500 | 115.2 | 100.6 | 115.1 | 100.4 | | 2000 | 78.7 | 120.2 | 78.5 | 120.0 | Pick-up from tickover to full throttle at speeds ranging from 1000 to 4000 r.p.m. was not affected by the suppressors. Misfiring was only obtained by running at full throttle at 600 r.p.m. with the ignition retarded to 1° A.T.D.C. and the air inlet temperature at 30° Cent. Under these conditions the engine would run steadily without suppressors but missed occasionally with them fitted. G.Wilson. | ||