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).
Technical page from a journal detailing procedures for engine knock intensity, mixture-ratio adjustment, anti-knock determination, and maintenance.
| Identifier | ExFiles\Box 27a\4\ Scan076 | |
| Date | 1st November 1931 | |
| 126 REFINER AND NATURAL GASOLINE MANUFACTURER NOVEMBER, 1931 laboratories will use secondary reference fuels for routine determinations.⁹ Such reference fuels may be straight-run or other stable gasolines suitable for the purpose. One of these should be of low anti-knock value, and the other of high anti-knock value; or, if a sufficiently high anti-knock fuel is not available, a mixture of the higher anti-knock fuel plus a knock suppressor may be used. These reference fuels should be calibrated on the octane scale against heptane and octane sufficiently often to insure accuracy of calibration; and, for every case where a fuel is rated by secondary reference fuels or by means of heptane and octane, the results should be recorded as an octane number. 7. KNOCK INTENSITY A tentative recommendation may be made that the knock intensity for use with the bouncing pin should be found by determining the compression ratio at which incipient knock occurs, and then increasing the compression ratio by 1.0 unit.¹⁰ Experience on the engine may make it necessary to change this recommendation. 8. MIXTURE-RATIO ADJUSTMENT When using the knockmeter it is unnecessary to take readings over a fixed period of time. To find the adjustment for maximum knock, note the meter reading and the micrometer setting. Then turn the micrometer screw, and note whether the meter readings go up or down. Slowly turn the micrometer in the direction in which the knock increases until the knock passes through a maximum. Check the point at least three times, and set the micrometer at the position of maximum knock. When using the gas-evolution burette, two readings over a period of one minute each should be taken as a measure of knock intensity. The carburetor is adjusted to the maximum-knock position, as in the preceding paragraph, by turning the micrometer and taking two one-minute readings at each position. Next place a blend of the low reference fuel and the high reference fuel in another gasoline container, estimating the proportions by the expected knock rating of the unknown fuel. Adjust the micrometer for this float bowl to the maximum-knock position as indicated above. 9. ANTI-KNOCK DETERMINATION With the float bowls thus set for maximum knock, take alternate readings on the two fuels. At least one minute should be allowed after changing from one fuel to another to allow the engine to reach equilibrium, and with certain fuels an appreciably longer interval is required. When using the knockmeter, the needle should be allowed to become stationary before the reading is recorded. When using the gas-evolution burette, at least two successive one-minute readings should agree. Take at least three alternate readings on each fuel. If the average of the readings on the unknown sample is higher than the average on the reference-fuel blend, repeat the readings with a blend containing a greater proportion of the low reference fuel. If the average of the readings on the unknown sample is lower than the average on the reference-fuel blend, repeat the readings with a blend containing a greater proportion of the high reference fuel. Continue in this manner until the readings on the sample are definitely higher than one blend and lower than another blend. For this bracket a value of two octane numbers is recommended as representative of the size now used by most laboratories.¹¹ The anti-knock value of the sample is obtained by interpolation of the figures so recorded, and is reported as the nearest whole number. When changing fuels in the containers, drain the previous fuel completely by means of the drain cock provided. Allow a small portion of the new fuel to flow through the line before closing the drain cock. 10. MAINTENANCE In the operation of the testing apparatus, it is recommended that a systematic schedule of inspection be carried out with the utmost care. Weekly inspections may be found advantageous from the standpoint of consistency of results. Bouncing pin. Tighten diaphragm retaining nut and clean off any carbon accumulation. In time the diaphragm will lose its temper and need replacement. These conditions manifest themselves by an irregular gas evolution or lack of sensitivity. Breaker-point clearance. The breaker-point clearance should be checked, and any pits which have formed dressed off. Spark plugs. The spark plugs should be cleaned and the porcelain inspected for cracks. The gap should be checked.⁸ Fuel system. Flush out the fuel system, and make sure there is no accumulation of foreign matter in the fuel containers, float bowls, lines or carburetor. Cooling system. Inspect for leaks, tighten or replace the pump packing as required. Combustion chamber. Inspect piston and cylinder head for character of carbon deposits. Excess carbon should be removed mechanically. Compression pressure. The compression pressure while motoring at 600 r.p.m. should be checked with a FOOTNOTES: ⁷ For the present the engine will include, as standard equipment, a bouncing pin and gas-evolution cell. The knockmeter may be supplied on the purchaser's request, at additional cost. ⁸ The question of spark plugs and spark-plug gaps is being studied, and the present recommendation is subject to change. ⁹ At present heptane and octane may be obtained from the Ethyl Gasoline Corporation, Yonkers, N. Y., at a price of $25 per gallon. Recently two secondary standards have become commercially available through the Standard Oil Company of New Jersey. These fuels have octane numbers of 50 and 68, respectively; and calibration curves are furnished with them (as determined on the Ethyl Gasoline Corporation, Series-30 knock-testing engine with the bouncing pin), giving octane numbers for these fuels blended with each other and with chemically pure benzene or tetraethyl lead. For tests of motor fuels, the data were obtained with very definite operating conditions and technique at a cylinder-cooling-medium temperature of 212° F.{Mr Friese} These fuels are supplied in 60 cents per gallon, in 10-gallon lots, or $1 per gallon in five-gallon lots. They may be ordered through Ross H.{Arthur M. Hanbury - Head Complaints} Dickson, Standard Oil Development Company, New York, N. Y. ¹⁰ Details of adjustment of the bouncing pin and instructions for dealing with difficulties in its operation are contained in Supplement “A.{Mr Adams}” ¹¹ This tentative recommendation is made with the understanding that the bracket size will be changed when and if further research so justifies. | ||