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).
Performance improvements for the 20/25 model, focusing on the ignition system and component changes.
| Identifier | ExFiles\Box 27a\1\ Scan191 | |
| Date | 12th December 1934 | |
| X4013 W/P - Sr. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}10/KW.12.12.34. Improved 20/25 Performance. We have at last got rid of the 20/25 head with the correct ignition governor. It was a good thing we kept it to complete this test because with the standard ignition governor the advance was far too great and you would have got exceedingly bad detonation with loss of power at 30 to 40 m.p.h. You will therefore note that you must use the ignition tyre provided, and the correct timing for the engine is 16° before top dead centre in the fully advanced position. This is 1.4" on the flywheel. They are contemplating fitting a high compression head to the Continental Trials 20/25 which is just coming off test, but I want to have your views on this head before I let them depart from standard on the Trials car. I suggest that you run the car on an intermediate brand of petrol in one of your tests to get an impression of what it would be like with 10,000 miles of carbon in it. You will of course appreciate that you have to use the special sparking plugs provided with the head. The standard plug pre-ignites badly. With regard to the ignition tyre, if you have any use for the one removed from the car you had better credit Derby with it; otherwise we presume it would be best to return it. Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} | ||