Hydrogen-injected internal combustion engine

The Hydrogen Injected ICE is an engine type used by the UNSC, and is featured in the M274 Mongoose Ultra-Light All-Terrain Vehicle and M12 Warthog vehicles.

Background
It is unclear exactly how the HI ICE works, but it presumably includes an internal combustion engine (Or ICE abbreviated).

The AMG 12.0 liter version used in the warthog makes a kind of whiny hum, and produces a significant amount of power (enough to propel 3 and one-quarter tons of 'Hog to 78 MPH). The 1000cc 4-stroke used in the Mongoose ULATV has a rough growl to it, especially when starting up.