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 engine performance and potential improvements between Rolls Royce and Bentley vehicles.
| Identifier | WestWitteringFiles\V\March1931-September1931\ Scan134 | |
| Date | 21th April 1931 | |
| HS.{Lord Ernest Hives - Chair} ) FROM R.{Sir Henry Royce} ORIGINAL CONFIDENTIAL E.{Mr Elliott - Chief Engineer} ) (At Le CanadelHenry Royce's French residence.) C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} (Struck through) C. to PN.{Mr Northey} DA.{Bernard Day - Chassis Design} (Struck through) RR. AND BENTLEY COMPARED. +3805. +3993. +7771 We always expect the Bentley to beat us on maximum speed, but generally in the past they were poor town cars and they were not very satisfactory in the hands of the owner for absence of trouble in very many ways. I have heard of valves, steering, bodies, cost of repairs, life, and permanent silence. We are bad for power at high engine speeds and we are over-geared for maximum speed. As the engine is at the present we should be better with double top about 12% above and below our present top. The double carburetters will give us 10/15% greater torque and about makes us equal at their 10% higher gear. We ought then to equal the 6.5 litre in maximum speed but not the 8 litre. With some further experience with these carburetters and a long duration camshaft with a slightly higher comp. ratio we might get to 95., but we can hardly hope to equal the 4 valve job. Our engine is the more practical and less costly to build. To really equal their performance per litre then we must have - (a) double top, (b) " carburetters, (c) long duration camshaft with increased comp. ratio to get nearer double valve maximum BHP. I do not consider there is anything about it mysterious or surprising. We should not be able to run our engine quite so fast because we have only single valves but I think these very high speeds very undesirable for life and reputation of the engine. Many times I have been very dissatisfied with our max: BHP. and there seems no reason why it should not equal the Bentley, but for the reasons given, which we must try to compensate for by (c). I was very pleased to see that our engine was equally smooth at high speed. We seem to be down very much in maximum speed - 15 MPH. To be comparable we should not be more than 5 less. Apparently a better maximum need not mean a rougher car or one with less good slow speed top gear performance. In this we hope to keep a little better at the expense of maximum, which is really quite unimportant to most owners, but may seriously affect sales. A supercharged 12 cyl. would be the real thing to go. A 6 cyl. is unsuitable for supercharging, I pointed out some time ago, because of high speed stresses, crankshaft periods, impossible to balance, etc. R.{Sir Henry Royce} | ||