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).
Summarizing engine alterations and performance test results for the Ulster Bentley.
| Identifier | ExFiles\Box 90a\2\ Scan148 | |
| Date | 25th July 1934 | |
| x7962 To SS.{S. Smith} c. to Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} c. to Hy.{Tom Haldenby - Plant Engineer} c. to Bn.{W.O. Bentley / Mr Barrington} ULSTER BENTLEY. We have completed the unit for this car. The attached report shows the tests which have so far been carried out. We have made the minimum alterations to the engine, which consist of a higher compression cylinder head having larger inlet valves, Aerolite pistons, and lead bronze big end bearings. We are using standard camshaft and valve springs. It will be observed that we have obtained approximately a 30% increase in power at top speeds and approximately a 20% increase in accelerating capacity at the intermediate speeds. On the road, on the fuel specified for the race it is almost entirely free from detonation. Its performance is much improved. It requires quite a normal type of sparking lug, and will idle below 500 r.p.m. On the track, under the conditions in which it will race (except for the passenger and tank fairings etc.), that is, with no head lamps, wings slightly narrower than previously and the spare wheel carried at the side, it lapped at 99.2 M.P.H. an increase of 9.2 M.P.H. since the special engine unit was fitted. The gear ratio is about right as 105 M.P.H. was reached at 4,500 R.P.M. where the wind was favourable. With fairings over the petrol tank etc. and a cover over the Passenger's seat, 1-2 M.P.H. should be picked up. The Hartford shock absorbers have improved the track holding of the car enormously. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||