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).
Study on the relationship between fuel octane number, engine design parameters, and engine knock, with supporting graphs.
| Identifier | ExFiles\Box 150\1\ scan0015 | |
| Date | 29th April 1935 guessed | |
| 6 DIVISION OF REFINING FIG. 6 L-Head, Single-Cylinder Engine. Bore, varied. Stroke, 3¾ in. and 5 in. Speed, 600 r.p.m. Throttle opening, full. Cylinder-head material, cast iron. Fuel Octane No., 80. Compression ratio, varied. Jacket temperature, 212 deg. F.{Mr Friese} Air-fuel ratio, maximum knock. Spark advance, maximum power. The Relation of Cylinder Displacement and Fuel Anti-knock Value to Indicated M.E.P. at Compression Ratio for Incipient Knock. FIG. 7 Speed for maximum torque. The Effects of Cylinder-Head Materials and Variation in Compression Ratio on the Fuel Anti-knock-Value Requirement and B.M.E.P. of a Single-Cylinder Engine. THE RELATION OF FUEL OCTANE NUMBER TO ENGINE COMPRESSION RATIO 7 other features of design which will minimize the effects of the differential expansion of aluminum and ferrous metals. FIG. 8 The Effects of Cylinder-Head Materials and Variation in Compression Ratio on the Fuel Anti-knock-Value Requirement and B.M.E.P. of an Eight-Cylinder Automobile Engine. Carbon, Rust, and Lime Cause Knock It is common knowledge that cars usually have less tendency to detonate when they leave the factory than at any time afterward. Such a progressive change in knocking tendency may be due to carbonization of the combustion chamber, rusting of the water jacket, or to the deposition of salts from cooling-water additions. Fig. 9 shows the increase in knocking tendency of the single-cylinder engine with carbon accumulation. Rust and lime deposits in the water jacket have an effect similar to carbon deposits. It will be noted that deposition, in addition to increasing the knocking tendency, reduces power output. Engine Speed Influences Knocking Fig. 10 shows that engine speed influences knocking tendency; in fact, many engines show an even greater change in required octane number for the same speed difference. Other types of engines may have their greatest knocking tendency at other speeds. Observations were not carried beyond 2,100 r.p.m. because of the disturbing effect of engine noise. It is apparent that if some means were developed which would prevent an engine from operating under full throttle at the speed of maximum knocking tendency, a higher compression ratio could be used. FIG. 9 The Effect of Combustion-Chamber Deposits on the Fuel Anti-knock-Value Requirement and B.M.E.P. of a Single-Cylinder Engine. FIG. 10 Bore, 3¼ in. Stroke, 3¾ in. Speed in r.p.m., varied. Intake air temperature, 85 deg. F.{Mr Friese} Throttle opening, full. Cylinder-head material, cast iron. Compression ratio, 5.75. Jacket temperature, 190 deg. F.{Mr Friese} Air-fuel ratio, 13.5. Spark advance, maximum power. The Effect of Variation in Engine Speed on the Torque and Fuel Anti-knock-Value Requirements of a Single-Cylinder Engine. | ||