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

Scale-focused performance from the O.S. Engine 91RZ-H

Scale helicopter pilots will value the O.S. Engine 91RZ-H for its rear-exhaust profile that preserves canopy lines while delivering practical, tunable power. The design balances visual accuracy with the mechanical improvements needed for reliable operation.

Refined intake and strengthened crankcase

Alterations to the intake porting and carburettor improve air and fuel delivery for cleaner combustion and steadier throttle response. The reinforced crankcase construction better supports the crank and thrust bearings during sustained or demanding use.

Pick the head that fits your model and flying

The 91RZ-H offers two head styles to match installation needs: a large blue anodised head for peak cooling when running hard, and a squared die-cast DH head where a lower profile and neat fit are priorities.

With thoughtful engineering and cooling flexibility, the O.S. Engine 91RZ-H is well suited to scale model pilots seeking authentic presentation together with consistent, controllable power.