Apparatus and process for measuring fuel octane numbers

In a process for determining fuel octane numbers from knock intensity signals generated by a test engine by comparing knock intensities of fuels of unknown octane numbers against knock intensities of fuels of known octane numbers, the improvement comprising, in sequence,

• i. operating the test engine on each fuel at a series of feed-rate settings for a time sufficient to generate a knock intensity signal for each fuel at each of the feed-rate settings, said knock intensity signals bracketing the feed-rate setting which gives the maximum knock intensity for each fuel,
• ii. calculating the approximate setting for each fuel at which the maximum knock intensity signal is generated,
• iii. operating the engine on each fuel at a narrower series of feed-rate settings than employed in (i), such settings bracketing the approximate maximum knock intensity setting as determined in (ii), to produce a refined feed-rate setting at which the maximum knock intensity signal is generated for each fuel,
• iv. storing the refined feed-rate setting of maximum knock intensity,
• v. operating the test engine on each fuel at the stored refined feed-rate setting at which the maximum knock intensity is generated, for a time sufficient to generate a new knock intensity signal, the test engine being operated on the fuels of known and unknown octane numbers in alternating sequence, and
• vi. calculating the octane numbers of the fuels of unknown octane numbers by comparing the new knock intensity signals produced in (v).