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).
Variations in cylinder head volumes on Bentley engines and the effect on compression and detonation.
| Identifier | ExFiles\Box 86\1\ scan0169 | |
| Date | 6th August 1935 | |
| To Sft.{Mr Swift} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} x19 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}16/KW.6.8.35. We have been checking over some cylinder head volumes on Bentleys. Attached is a copy of some of the figures we have obtained. You will see that in one case the variation from one cylinder to another was nearly 5%. You will recollect how particular the Americans are that their combustion chambers should be the same volume, and that Packards had a special arrangement for checking combustion volume. At one time we believe that you were considering making a definite check on all cylinders and correcting them. As compressions rise, the necessity for some check becomes of increasing importance. As an example, on the high compression 7 to 1 Bentley head a decrease of 5 c.c's raises the compression ratio from 7 to 1 to 7 1/4. At 7 1/4 the head will definitely detonate on standard fuel, whereas at 7 to 1 it is reasonably free from this trouble. We understand that no limit is given on the drawing but that some instructions have been issued in memo, form by BY.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||