Highest useful compression ratio (HUCR) is the highest compression ratio at which the
Highest useful compression ratio (HUCR) is the highest compression ratio at which the Correct Answer Fuel can be used in a test engine without knocking
Highest Useful Compression Ratio (HUCR) is the compression ratio at which a fuel can be used without detonation in a specified test engine under specified operating condition and the ignition and mixture strength being adjusted to give best efficiency