O.S. Engine 91RZ-H Rear-Exhaust Ringed Helicopter Engine  [OSMG1978]

Authentic canopy fit and performance from the O.S. Engine 91RZ-H

For model helicopter enthusiasts chasing authentic appearance, the O.S. Engine 91RZ-H blends a rear-exhaust form factor with engineering aimed at smooth, dependable output. It installs cleanly in scaled fuselages and supports precision flying.

Improved airflow and durable internals

The 91RZ-H's updated intake porting and carburettor setup boost airflow efficiency, improving mixture control and throttle feel. The reinforced crankcase gives stronger support to the crank and thrust bearings, helping the engine run reliably under higher loads.

Cooling configurations to suit your build

Two head choices let you tailor cooling to the mission: the larger blue anodised head for maximum heat rejection, or the compact squared die-cast DH head for a low-profile installation that still provides effective cooling.

Whether you fly static scale displays or active sport sessions, the O.S. Engine 91RZ-H offers a practical mix of authenticity and usable power, backed by sound construction and head options for different setups.