Ace Electronics

Thunder Tiger - F-91S 4-Stroke Engine


A great way to enjoy the advantages of four-stroke performance!

F-91S 4-Stroke Engine

Product No. 9804

All Thunder Tiger engines have been designed to combine high performance with easy handling and maintenance using CAD computer technology, resulting in consistent high quality and reliability. Subjected to rigorous quality control check ensures that it will provide years of trouble free use.

The Four Stroke series are manufactured by automated computer-controlled machinery, resulting in a product that looks and performs better. Special Camshaft and oversize valves combine to improve performance and ease handling. Precision air bleed carburetor makes adjustments simple, and efficient mufflers keep things quiet at the field. Perfect for the pilot looking for the authentic aircraft sound.

A Closer Look


  • Top grade CNC equipment, state-of-the-art technology are used.
  • Improved carburetor; swept back for safety, which makes adjustments simpler.
  • Forged aluminum connecting rod with dual bushings connects it all together.
  • Improved quality; ISO9001 Certified which guarantees the maximum power and performance.
  • Smooth running and long lasting power plant with front and rear ball bearings.
  • Authentic aircraft sound.
  • Ringed-type piston.
  • Designed for both beginners and experienced modelers.


  • Fuel: 18% lubricant and 10-15% nitro content, synthetic/castor blend lubricant recommended
  • Propeller: Break-in: 11x10; Stunt/Aerobatic: 11x10, 11x11, 12x10, 12x11, 13x9; Scale: 14x7, 15x6, 16x6, 12x8 (3-blade)
  • Glow starter, plug wrench and field equipment


  • Displacement: 0.91 cu in (14.97 cc)
  • Bore: 1.114 in (28.3 mm)
  • Stroke: 0.937 in (23.8 mm)
  • Crankshaft: 5/16 x 24
  • Practical RPM: 1,800 ~ 12,000
  • Output: 1.6 BHP @ 11,000 RPM
  • Weight w/o muffler: 25.7 oz (730 g)