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).
Comparing the 20 HP model's engine performance against competitors and considering an increase in bore and stroke.
| Identifier | Morton\M2.1\ img045 | |
| Date | 3rd April 1928 | |
| -2- Hsl/LG3.4.28. on the 20 HP. This has about counterbalanced the increase in chassis weight. Our competitors however have had the same advantage in reduction of body weights. The Bentley found it necessary to increase the size of their 3-litre car in order to give a reasonable performance and comfortable body. The Sunbeam have increased the size of their engine on the 3-litre 6-cyl. car. The Chrysler have also a larger engine. The comparative sizes are:- Cyl. capacity Bore and Stroke. 20 HP. RR. 3132 c.c's 3 x 4.5" Sunbeam 25 HP. 3619 3.15 x 4.72" Chrysler 23 HP. 3580 3.12 x 4.75" If we try and obtain the same performance with a smaller engine we are always at a disadvantage especially when we are expected to give extra smoothness and silence as well. We favour .125" on the bore, and .25" on the stroke. We are hoping that we can stand this amount without increasing the weight of the chassis or transmission so that all the extra power would go to improving the performance. We do not consider that this slight increase in size would affect the Phantom sales. What it would do would be to satisfy a number of people who are at present delighted with the 20 HP. except that it has not got a sufficiently good performance. At the moment we are not satisfied that we can retain the present smoothness if we obtain the extra power by increased | ||