Alpha-Otto Technologies with new engine concept: This 2-stroke engine is intended to secure the future of combustion engines

When most people think of two-stroke engines, they probably think of the Trabi, some DKW models, motorcycles (primarily enduros and scooters), or lawnmowers. However, many decades ago, significant disadvantages of this engine concept became apparent – especially in the passenger car sector – which led it to lose out to four-stroke engines. In particular, the high emissions caused by the combustion of oil, which also contains unburned fuel, and the poorer fuel consumption led automakers to favor the four-stroke engine early on.

Today, this engine concept is largely extinct in automotive engineering, but perhaps a glorious comeback is imminent. Alpha-Otto Technologies, a US company based in Detroit, the US's motor city and founded only in 2022, is working on a new type of two-stroke engine that will secure the future of the internal combustion engine. The great special feature of this new development: The engine, dubbed "REV Force" by the Americans, is said to be capable of running on "almost any combustible fuel" (Alpha-Otto's own words). In addition to gasoline, diesel, and kerosene, this should include carbon-free alternatives such as pure ethanol, ammonia, and hydrogen.

Company founders and designers John L. Krzeminiski and David D. Dusseau conducted initial bench tests with a version of the engine featuring two parallel cylinders, supercharged by a compressor. The water-cooled engine, weighing just under 48 kilograms and measuring 38 centimeters long, 35 centimeters wide, and 30 centimeters high, reportedly developed 175 hp. According to Alpha-Otto, even 223 hp and a maximum of 176 Newton meters are possible.

The thermal efficiency of the Alpha-Otto REV Force is expected to be 50 percent, which would be truly top-of-the-line among combustion engines – especially in the passenger car sector. "Our technology offers a highly efficient, fuel-flexible solution that delivers reliable and switchable power, leveraging today's infrastructure while seamlessly adapting to tomorrow's infrastructure," says Krzeminiski. The compression ratio in the base configuration is 10:1, and the maximum possible speed is expected to be 8,000 rpm.

This two-stroke engine, like a four-stroke, is lubricated with a dry sump system, meaning no oil is burned. Unlike traditional two-stroke engines, there's an electric rotary valve in the engine's exhaust port, essentially a rotating exhaust valve. The REV-Force engine also doesn't draw its air-fuel mixture from the crankcase, allowing it to be lubricated with oil (as in a four-stroke engine). Instead, the supercharger controls the air supply. Alpha-Otto has also added fuel injection. The fuel is only injected after the rotating exhaust valve closes, preventing unburned fuel from entering the exhaust gases.

To enable the innovative two-stroke engine to burn the promised variety of fuels, the REV-Force two-stroke engine features sophisticated software control. Depending on the fuel it is fed, it is said to be able to adjust compression, displacement, ignition timing, and ignition settings in a flash.

According to the developers, the REV Force engine will run extremely lean, which would reduce fuel consumption. Fuel consumption and emissions will be reduced to "unprecedented levels," according to the promise; however, Alpha-Otto hasn't provided any specific figures. The Americans plan to use exhaust aftertreatment technologies to meet the most stringent current and future emissions standards.

The concept is also said to offer advantages on the cost side. A two-stroke engine requires fewer moving parts than a four-stroke engine, eliminating the need for camshafts and valve assemblies. This makes it not only lighter and more compact than a four-stroke engine, but also easier to maintain and more cost-effective to produce.

It's still unclear how far Alpha-Otto is from series production of its REV-Force engine. According to its crowdfunding campaign, the American company is "close to commercializing" the patented engine design. Incidentally, the engine doesn't necessarily have to be used in a vehicle. According to Alpha-Otto, it could be used as a power generator, as well as integrated into hybrid powertrains.