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).
Preliminary test results comparing the lighter Phantom engine to the standard model, focusing on weight, compression, power, and detonation.
| Identifier | WestWitteringFiles\P\October1926-November1926\ Scan011 | |
| Date | 26th October 1926 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/ACL. c.c. to BJ. Mor. c.c. to R.{Sir Henry Royce} RG.{Mr Rowledge} c.c. to DA.{Bernard Day - Chassis Design} EY. c.c. to CY. ORIGINAL Hs{Lord Ernest Hives - Chair}/ACL2/LGS.10.26. LIGHTER PHANTOM ENGINE. We have had the lighter Phantom engine running and made some preliminary tests with regard to its power and detonating propensities to afford a comparison with the standard Phantom. The cylinder block units and the head result in approximately 100 lbs. saving in weight over the corresponding standard unit. The compression ratio was measured and found to be 4.45 to 1. The ratio used on the standard Phantom is 4.1 to 1 and on this engine is found to be about the limit imposed by the tendency of ordinary commercial petrol to detonate at low speeds and on 'picking up'. Our general impression of this engine is as follows :- The power output is higher than the standard engine and is approximately what we should expect from the increase in the compression ratio alone assuming the I.H.P. to be proportional to the air standard efficiency - which assumption has been borne out by previous tests. Audible detonation is evident up to a speed of approx. 750 r.p.m. full load with the ignition and mixture adjusted in the most efficient position. The detonations with this ratio are more severe than on the standard engine with its 4.1 to 1 contd :- | ||