Commonly Used Abbreviations - General Information: "H"

HAC: High Altitude Compensation
HC: Hydrocarbons
H/D: Heavy Duty
HO2S: Heated Exhaust Gas Oxygen Sensor
Hg: Mercury
Hgt.: Height
HLDT: Headlight
HO: High Output
HO2S: Heated Oxygen Sensor
HP: High Performance
HSC: High Swirl Combustion
HSO: High Specific Output
HTR: Heater
Hz: Hertz (Cycles Per Second)