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).
Tests conducted after removing the turbulent lip from a 20/25 4¼ bore cylinder head Lec.5002.
| Identifier | ExFiles\Box 86\1\ scan0187 | |
| Date | 20th March 1936 | |
| To E.{Mr Elliott - Chief Engineer} c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} SECRET. X219 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}19/KW.20.3.36. Removal of the Turbulent Lip from the 20/25 4¼ bore Cylinder head Lec.5002. We have carried out tests removing the turbulent lip on the cylinder head. Attached are the results obtained. Briefly, there is little to choose between the two cylinder heads with regard to the highest output which can be obtained for a given degree of detonation. On the other hand, the head with the turbulent lip removed indicates that the rate of burning has been reduced because it requires 3° more advance for maximum power. We anticipate that this may give us a smoother engine on the road, but it is difficult to get a value for an alteration like this, and it will be some time before we can form a definite opinion. By way of confirmation, we attach some Bentley figures taken a short time ago which again indicate that the turbulent lip has also on this head only a slight effect on detonation, though a very marked effect on the amount of ignition advance required. We propose, as opportunity occurs, to carry out some tests on the old open type 25 HP. head to complete the investigation. The ignition advance curve required by the 20/25 head without the lip presents a problem for the present Rolls-Royce governor which will be dealt with separately. We shall shortly have enough spare Ph.III cylinder heads to repeat the 20/25 HP. experiment on one of those units. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||