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).
Analysis of engine detonation, comparing different cylinder constructions and valve types.
| Identifier | ExFiles\Box 178\4\ img094 | |
| Date | 18th May 1932 | |
| (3) is most marked. A characteristic of the detonation marking, common to our poppet valve engines, is also evident, i.e. in the poppet valve types the detonation marking has occurred at the inlet end of a diameter, approximately at 90° to a line through the centre of the spark plugs. The failure to detect detonation by ear during the Type Test again raises the point which was remarked on in reports, ref. Ha/Dor.{Mr Dorey}4/MJ.15.10.31. and Ha/Yng.1/KT.31.12.31., dealing with the two piece cylinder construction, and this further evidence seems to prove conclusively that the audible method of measuring detonation is quite useless when a comparison between two different types of cylinder construction is to be made, as apparently the acoustic properties of the sound waves produced by the pressure waves inside the cylinder, depend entirely on the type of cylinder construction. In order to investigate this point, we propose to look into the question of producing a suitable indicator valve for the sleeve valve cylinder to obtain diagrams which may be compared with ones taken from a standard cylinder running under similar conditions. Reasons for the cause of the excessive detonation may now be considered. A detonation test made prior to type test with the old cylinder blocks, 12 m.m. spark plugs, and the same compression ratio (6.6/1) gave 'Y'4 ft. at 1700 RPM. full throttle on DTD.134 fuel. With the new cylinder blocks and 14 m.m. plugs and other conditions exactly as before detonation at 2250 RPM full throttle was - 100 ft. The possibility of the spark plugs causing trouble may definitely be ruled out as at the end of the run these were in excellent condition. With regard to the cylinder blocks. The two sketches appended show slight alterations which have been made to the contour of the inlet ports by the addition of metal for the purpose of strengthening the block. When alterations were last made to the effective porting by dropping the lower head lands, an increase in detonation resulted - report ref. Ha/Yng.1/MJ.14.10.31., and it was necessary to lower the compression ratio in order to make the engine run satisfactorily at full throttle on standard fuel. For the next tests leaded fuel will have to be used, since the design does not permit the compression ratio to be lowered further. During these tests we propose to replace the second spark plug in several of the cylinders by a thermo couple, in order to obtain some comparative temperatures between the individual cylinders. One of the chief claims for the sleeve valve construction is that it eliminates the hot exhaust valve, thereby reducing detonation. At the moment it appears that the 'dry liner effect' | ||