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REX-B: Founder´s Edition.
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VAT Excluded.

Direct bank transfer only.

Delivery date: January 2023

Out of stock


All the quality and performance of the REX-B with the exclusivity of the First Edition.

With the REX-B: Founder´s Edition we want to give you a chance of being part of the INNengine story. A rare opportunity of being able to acquire a technological collector’s item: the first final prototypes used to validate our technology before series production.

This exclusive First Edition, limited to 11 units, has been made by combining cutting-edge technology such as 9-axis precision machining (no casting) with the care and detailed handcrafting of its inventor: Juan Garrido Requena. These very units will be tried and tested under various conditions and environments to ascertain power delivery and product durability.

100% machined using 7075-T6 aerospace aluminum, hand sanded, filed edge by edge, tested and assembled one by one. This is the first and last chance to get your hands on one of these handcrafted REX-B prototypes which, in addition to the many particularities compared to those that will be available for pre-order, will include other value-added features such as a numbered Founder’s Edition plaque, a precision aeronautical aluminum rotating pedestal, a hand-signed certificate of authenticity and much more.

Developing new engines is a costly process and, with 100% of the proceeds from the sale of this exclusive First Edition being reinvested to further R&D in the INNengine platform, what better way of both acquiring an appreciating asset while contributing towards this world-changing enterprise?

There are only 11 REX-B: Founder´s Edition engines and will be delivered on January 2023 in a first come first served basis. Order yours now before they are gone!


  • Ultra-compact platform starting from just 214mm in length and 146mm in diameter.
  • Aerospace-grade aluminum construction bringing weight down while offering extreme toughness and durability.
  • 4-cylinder camtrack configuration with simple harmonic cinematic: suppresses both primary and secondary imbalances. No need to compensate.
  • INNengine’s patented 1Stroke technology: offering twice the power delivery of a 2Stroke with the same power periodicity delivery of a V8 engine.
  • Enhanced Equal Engine air cooling system: having all 4 cylinders axially oriented against the airflow means equal cooling throughout the platform and of each cylinder as well as optimum refrigeration with the hotter areas exposed directly against the wind flow ensuring reliable functioning under the most demanding situations.


  • ENGINE BLOCK: aerospace grade aluminum 7075-T6 precision CNC machined and treated by hard anodizing. Top quality hardened steel guide rods, rectified & super finished.
  • CAMTRACK: proprietary hardened and spring temper steel treatment, 9-axis precision CNC machining for 3D curvature camtrack: suppressing over accelerations. Low temp nitruration post treatment & super finishing.
  • 1S 4R-AXIAL® CYLINDER: aerospace aluminum 6082-T6 fully precision CNC machined (no casting for max quality). Nikasil treatment and burnish post-treatment for improved surface strength.
  • PISTON BODY: aerospace grade aluminum 7075-T6 precision CNC machined and treated with an 80-micron hard anodizing layer.
  • PISTON HEAD: aerospace aluminum 6082-T6 fully precision CNC machined (no casting for max quality) with the new coupling system allowing for improved truncated cone piston shape.




125.7 cc

Power output

22.7HP@ 6000rpm


L:214mm x ⌀146mm



Cylinder bore/Stroke

⌀40mm / 25mm

Speed range

600 – 6000 rpm

Cylinder arrangement

1S 4R-Axial® INNengine patented technology



Lubrication ratio


Compression ratio


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