O.S. Engine 91RZ-H DH Rear-Exhaust Scale Helicopter Engine  [OSMG1979]

Precision Power for Scale Helicopters: O.S. Engine 91RZ-H DH

For RC helicopter builders seeking authentic performance and fitted proportions, the O.S. Engine 91RZ-H DH delivers measured power and engineering accuracy. Its rear-exhaust layout was developed to sit neatly inside scale canopies while preserving model lines and balance.

Engine Performance and Build Details

The O.S. 91RZ-H DH combines a 0.91 cu in displacement with 3.3 horsepower at 15,000 rpm to offer a practical operating window from 2,000 to 16,000 RPM. Careful porting and a revised crankcase increase stability under load, giving predictable throttle response for precision flying.

Cooling Choices to Suit Your Installation

This engine includes two heat sink head options to match installation and cooling needs: a larger blue anodized head for stronger heat rejection, or a compact squared die-cast head for tight engine bays. Pilots can pick the head that best fits their canopy and cooling requirements.

Maintaining Scale Appearance and Fit

The rear-exhaust format of the 91RZ-H DH keeps exhaust routing out of sight and helps maintain the streamlined silhouette of scale helicopters. It is a practical solution when retaining authentic bodywork is a priority.

The O.S. Engine 91RZ-H DH is well suited to modelers who prioritise realistic installation and steady power delivery. Its flexible cooling options and tuned internals make it a dependable choice for scale helicopter projects.