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).
Peugeot and Duesenberg engine performance, focusing on compression and mean average pressure.
| Identifier | ExFiles\Box 19\7\ Scan051 | |
| Date | 18th May 1920 | |
| X.790. To SA. from R.{Sir Henry Royce} Copy to CJ. " " Bn.{W.O. Bentley / Mr Barrington} " " PN.{Mr Northey} " " Hs.{Lord Ernest Hives - Chair} X.821. - Peugeot Car. X.490. Many thanks for your cutting re the Peugeot and Duesenberg. In the translation paragraph 3, there is a question of compression - this is not in Mons. Faroux's article. An indicated average pressure should not be confused with the compression. It is unfluenced by the compression. We do not know the compression ratio of these engines, which depends upon the space above the piston at the top of the compression stroke, or the compression pressure which depends upon the amount the engine fills up, and also the space above the piston. They are aiming at in the claculations of the two engines the mean average pressure as indicated by the brake H.P. This is generally in the neighbourhood of 110 lbs to the square inch, which equals 7.733 kg. per sq. cm. for the best H.P. and we have obtained for the maximum average pressure as much as 130 lbs. per square inch which equals 9.49 kg sq./cm. as maximum at a speed somewhat below that of the maximum H.P. I should very much doubt if the Duesenberg obtained the average mean pressure at 3,300 revs. per minute which is necessary in a 3 litre engine to give 165 B.H.P.at that speed. Moreover, it is not the maximum H.P. available so much as the average H.P. of the engine which can be used during a race which tells. Contd. | ||