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).
Cold starting tests for the Wraith engine, comparing its performance with Bentley and other models.
| Identifier | ExFiles\Box 151\3\ scan0363 | |
| Date | 4th March 1938 | |
| -3- WRAITH COLD STARTING TESTS. Considerable difficulty has been experienced in starting the Wraith engine after standing all night in a temperature below freezing point, and several times it has been necessary to short circuit the ballast resistance before a start has been possible. We have taken tests with the object of trying to improve the start and also to compare it with that of the Bentley, which it is claimed, is good. All the tests have been taken in the cold chamber with the temperature down to 8°F which should give sufficient margin for any condition experienced in the service of a customer. In comparing the Bentley start against that of the Wraith we would say from results that the difference lies in the higher engine torque of the Wraith from cold, giving less R.P.M. than that of the Bentley. A start was obtained on 5.B.IV with both Bentley and Wraith batteries. We also think the Bentley battery is better than the proposed Wraith, but they are confirming this on a bench test. With a view to finding the best combination on 28.G.VI to give us the highest voltage at the coil, the highest R.P.M. of the engine, and, of course, the better start we compared the Wraith, Bentley, P.III and 25/30 standard batteries. The P.III and the 25/30 batteries as the figures show gave an increased voltage to the ignition and a higher R.P.M. of the engine, the 25/30 having the best starting torque of all. Starts from colder were then tried using a Delco coil in conjunction with the four batteries mentioned. On each test the car was in the cold chamber all night. | ||