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).
Comparison of horsepower between a standard 3.25 and a proposed 3.5 Bore Bentley at various road speeds.
| Identifier | ExFiles\Box 82\4\ scan0146 | |
| Date | 22th July 1935 | |
| x209 3.5 BORE BENTLEY Sg{Arthur F. Sidgreaves - MD} Replying to your query. The large bore Bentley is practically equivalent to fitting a 16% lower axle ratio to the existing car, without a corresponding increase in fuss and engine speed. At 80 MPH the large & small bore give the same Horse Power, | ROAD SPEED 10x41 AXLE MPH | STANDARD 3.25 BENTLEY | PROPOSED 3.5 BENTLEY | |-----------------------------|-------------------------|----------------------| | 20 | 30 H.P. | 35 H.P. | | 40 | 66 H.P. | 76 H.P. | | 60 | 97 H.P. | 110 H.P. | | 80 | 118 H.P. | 118 H.P. | | 90 | 110 H.P. | 110 H.P. | The benefit obtained is at the lower speeds. Having once established the large bore we shall develop it to give a 16% increase at the top as well as the lower speeds. Rm.{William Robotham - Chief Engineer} | ||