Rotary engines based on the Wankel principle were developed with
two fundamentally different approaches to cooling the rotor.
Mazda, Audi, Suzuki, Ingersoll-Rand and others used the oil-
cooled rotor. It is an expensive, heavier and more complicated
design, which achieved specific fuel consumption in the range of
.55 to .6 lbs/hp hr. This is about 15% to 20% poorer than a
typical four-stroke piston engine. The other approach taken by
Outboard Marine Corporation (OMC), Fichtel Sachs and Norton was
to use the incoming air-fuel mixture (“charge”) to cool the
rotor. This design was much lighter, less expensive and through
the use of roller bearings and very low rotor cooling losses
achieved a specific fuel consumption between .45 and .5 lb/hp
hr, which was close to the 4-stroke piston engine. Historically
all of the charge-cooled rotary engines that were developed used
an arrangement where the fuel-air mixture passed through the
rotor from one side to the other. This design cooled the rotor
unevenly, which lowered