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 performance of different sparking plugs on the Peregrine model during road tests.
| Identifier | ExFiles\Box 162\4\ img308 | |
| Date | 15th May 1933 | |
| X1918 C. Files. ----- 15.5.33. ----- X44256 SPARKING PLUG PERFORMANCES ON PEREGRINE. During recent road tests with semi-expanding carburetter to LeC.3157 considerable trouble was experienced with picking up from 10 m.p.h. full throttle. This trouble was found to be due to misfiring at low speeds, the plugs used at the time being KLG. LKS.6 type, these were changed for KLG. 744 type which is low voltage aero plug, and no further trouble was experienced. KLG. 744 type of plug is, however, very poor for slow running and idling, this is probably due to the small gap, which is only .018", the standard aero practice. The mixture with this carburetter up to 35 m.p.h. is much weaker with the two S.U. carburetters so that faults in the ignition system are easily shewn up. Below is a brief summary of the performance of each type of plug tried, these plugs were only given short tests so that we cannot say how they will stand up to prolonged runs at high speed. KLG. LKS.6 Reach .700 Very poor for picking up under full load. Slow running poor. Idling poor. KLG. 744. Reach .475 Good pick up under full load. Slow running poor. Idling poor. KLG. 765 Reach .650 Pick up good from 10 m.p.h. full throttle. Slow running 5 m.p.h. minimum. Idling lumpy. Lodge X.335 Reach .550 Pick up good (from 10 m.p.h. full throttle) Slow running 5.m.p.h. minimum Idling lumpy. | ||