INNegine: A Spanish engine with the potential to revolutionise the automotive and aeronautics industry

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INNengine, a Spanish manufacturer based in Granada, is developing a new internal combustion engine design that promises an unprecedented ratio of weight, size and power.

"INNengine, a Spanish manufacturer based in Granada is reviving the idea of revolutionising the automotive industry through a new internal combustion engine design. Its innovative engine promises to achieve an unprecedented weight, size and power ratio compared to conventional internal combustion engines. This breakthrough is seen as a kind of holy grail for diesel and petrol engines, although its viability in the market and in our future cars is still in doubt.

The INNengine is based on opposed piston engines, a design that dates back to 1882 and was introduced by James Atkinson, who also gave his name to the Atkinson duty cycle that is widely used in hybrid engines today. However, we are not referring to the boxer engine architecture used by Subaru or Porsche, but to two pistons working opposite each other within a single cylinder. Over the years, this design has been studied in various laboratories and engineering companies because of its advantages in terms of performance, efficiency and fewer moving parts. So far, however, no one has succeeded in bringing this type of engine to a large-scale commercial application.

The great advantages of opposed piston engines lie in their high level of efficiency, their smooth operation with almost no vibration and the reduction of moving parts, such as the valve train. Throughout history, opposed-piston engines have been used in specific applications, such as military vehicles, ships, trains and aeronautical applications. However, the idea has continued to evolve, finding its most modern and optimised version in the design developed by Achates Power.

The INNengine concept turns the "original" opposed-piston engine design on its head, reducing the weight and size of the engine. The key to this reduction lies in eliminating the traditional design of pistons connected to a crankshaft and replacing it with a rotating cam on which the connecting rods are supported. In addition, a permanent contact track is used where the axial movement of the pistons is transformed into circular motion on a single output shaft. In short, the real innovation behind the INNengine has been to simplify the design of opposed piston engines further.

The INNengine consists of 8 opposed pistons in 4 cylinders and, with a displacement of 500 cc, is expected to deliver performance equivalent to that of a conventional 2-litre engine. So far, INNengine has not reported any official data on fuel consumption, power or torque. The latest prototype developed has a very small size and a weight of 43 kg, but further development is expected to reduce this weight to 35 kg.

If we look at the two opposed piston engines discussed today, Achates Power and INNengine, both are backed by Saudi Arabian giant Aramco. In both cases, though, these designs still need some development time to become a reality on the streets, especially with the financial backing of a major manufacturer to enable large-scale production. Recently, Achates Power has managed to attract the attention of Cummins and ARPA-E to invest in its development, while INNengine has not yet confirmed any investors for this purpose.

Despite this, the INNengine project continues to progress and is currently installed as the main engine in a Mazda MX-5 NB1 used as a test car. The purpose of this test car is to evaluate the engine's performance under real-world conditions, and a further evolution of the engine is expected in the near future. However, INNengine does not see this application as the future of its design, as the automotive industry is focusing all its efforts on electric motors. It is difficult to find a manufacturer willing to invest in the development of an internal combustion engine in these times when the major automotive groups have frozen their investments in combustion engines to focus on batteries, power electronics and electric motors.

Therefore, if this project born in Armilla (Granada) comes to fruition, its future could lie in range extenders for electric vehicles. Its small size and weight are key elements for this application, promising silent operation and high efficiency. Other manufacturers are also exploring the use of rotary motors to mitigate the extra weight and cost of using large batteries".



INNengine: así es el motor español que podría cambiarlo todo, o no. | Diario Motor, Retrieved June 1st, 2023, from:

Ni híbrido, ni eléctrico, el motor español que habla de revolución estará listo este 2023 y podrá funcionar con hidrógeno. | Diario Motor, Retrieved June 7th, 2023, from:

El motor térmico español INNengine puede revolucionar la industria del automóvil. | Top Gear, Retrieved May 29th, 2023 from:


El primer motor español en 50 años, listo para poner patas arriba el sector | Auto Bild, Retrieved May 30th, 2023, from:

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