Complex sentence: First available on Navistar's 7.3L/444 cubic-inch, V8 diesel engine, HEUI used engine oil pressure to power high-pressure fuel injection, in contrast to the traditional method of unit-injector operation via the engine camshaft.
Split into simpler sentences: First available on Navistar's 7.3L/444 cuin, V8 diesel engine. HEUI uses engine oil pressure to power high-pressure fuel injection, where usual method of unit injector operation is the engine camshaft.