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

Real scale flight with the O.S. Engine 91RZ-H

Pilots of scale helicopters, take note. The O.S. Engine 91RZ-H combines a rear-exhaust layout that fits neatly under streamlined canopies with engineering focused on reliable, controllable power. It blends authentic appearance with practical performance for scale setups like Hirobo models.

Precision engineering for steady power delivery

The O.S. Engine 91RZ-H benefits from revised intake porting and an updated carburettor arrangement that improve mixture control and throttle smoothness. Its strengthened crankcase supports the crank and thrust bearings better under heavy loads, helping the engine stay dependable during long flights.

Choice of cooling heads for your flying style

To suit different installation and cooling needs, the 91RZ-H is available with two head options: a large blue anodised heat sink for high cooling demand, or a compact squared die-cast head (DH) for a tighter, cleaner fit that still provides effective heat dissipation.

For scale enthusiasts wanting both authentic looks and usable power, the O.S. Engine 91RZ-H delivers a balanced package with robust internals and flexible cooling options that suit a range of flying styles.