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).
Report comparing engine starting performance between Wraith and 25/30 chassis with different ignition coils and batteries.
| Identifier | ExFiles\Box 151\3\ scan0369 | |
| Date | 4th February 1938 | |
| -3- Rm {William Robotham - Chief Engineer} /RC. {R. Childs} 1/MH. {M. Huckerby} 4.2.38. starting. In these tests the engine was made to turn over by means of the starter for 15 seconds with the ignition switched "off" at the end of this time a further test was made with the ignition switched on and 40 seconds allowed for a start to be made. The results show that the Wraith fitted with a Delco-Remy coil made a good start, but when fitted with the 20,000 turn Wraith coil, fired but would not start on one test, but started on another test. On the other hand the 25/30 chassis would not even fire. Another 25/30 chassis was tried, and this started, with difficulty, under these conditions. Summing up, the Wraith with its own ignition but fitted with a 25/30 type battery is no worse for cold starting than the 25/30 chassis, but when fitted with a Delco-Remy coil is better. Under normal conditions the 20,000 turn R.R. coil has proved itself very efficient with regard to "pick-up" and high speed running, it also has a low running temperature: but with regard to running under conditions of very low primary current both the Lucas and the Delco-Remy give a slightly better performance. Chassis | Type of Battery. | Ignition Volts. | Starter Volts. | Battery Volts. | Battery Current | S.P.G. Acid | Engine R.P.M. 28.G.VI | Wraith | 5.5-6.0 | 5.7-6.2 | 7.0 | 232 | 1.285 | 40 No Start. 25/30 | 25/30 | 6.8-7.0 | 6.3-6.5 | 8.0 | 272->232 | 1.265 | 60 No Start. 28.G.VI | 25/30 | 7.5 | 6.8 | 8.5 | 220 | 1.270 | 60 fire after 2 seconds. 25/30 | Wraith | No Start | | | | | 56 28.G.VI | 25/30 | Fire but no start | | | | | 28.G.VI | 25/30 | 20,000 coil replaced by Delco | | | | | Start. Rm {William Robotham - Chief Engineer} /RC. {R. Childs} | ||