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

O.S. Engine 91RZ-H Rear Exhaust Ringed Heli Engine
Price:
NZD$581.44
Brand:
O.S. Engine
Model:
OSMG1978
Condition:
Brand New
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Scale realism powered by the O.S. Engine 91RZ-H

Scale helicopter modelers will appreciate the O.S. Engine 91RZ-H for its rear-exhaust design that complements sleek canopies. It is engineered to offer credible scale looks while delivering practical, controllable performance for flight displays.

Redesigned intake and robust crankcase support

The intake porting and carburettor layout on the 91RZ-H have been improved to enhance airflow and combustion stability. The updated crankcase also provides better support for the crank and thrust bearings, increasing engine longevity under load.

Two head designs to match your installation

Choose between the large blue anodised heat sink head for maximum cooling in demanding use, or the squared die-cast DH head when a compact, neat installation is preferred without sacrificing cooling capability.

Specifications

  • Displacement: 0.91 cu in (15 cc)
  • Bore: 1.09 in (27.7 mm)
  • Stroke: 0.98 in (24.8 mm)
  • Practical RPM: 2,000-16,000
  • Output: 3.3 hp @ 15,000 rpm
  • Weight w/o muffler: 21.3 oz (605 g)
  • Includes: #8 glow plug

With sound engineering and adaptable cooling choices, the O.S. Engine 91RZ-H is a capable choice for scale flyers who want both period-correct looks and dependable engine behaviour.

Does the rear-exhaust affect aircraft balance?

The rear-exhaust layout is typically neutral for balance when installed correctly; weight placement and muffler mounting should be considered during installation to preserve the centre of gravity.

Will I notice better midrange power with the new porting?

Yes, the improved porting and carburettor tuning aim to stabilise midrange combustion, resulting in a more usable power band and less hesitation across throttle changes.

How to pick between the two head types?

Select the blue anodised head for intense flying sessions where heat is a factor. The squared die-cast DH head is ideal when you need a tidy silhouette and sufficient cooling for routine flying.

What maintenance does the 91RZ-H require?

Regular glow plug checks, carburettor tuning and bearing inspections are recommended. Keep the cooling fins clean and verify muffler and engine mounts after initial run hours.

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