With a mantra like “the future is eclectic”, we expect something interesting from INNengine, a startup based in Spain. The company is demonstrating a “single-stroke” engine that works by opposed pistons with wave-like twist.
“One-stroke” is in quotes because the engine is actually two-stroke (by definition) because it has two movements (strokes) during combustion. However, unlike most conventional two-stroke engines, the INNengine e-Rex doesn’t burn oil, or even use one of those strokes to lubricate or cool itself. These all happen individually, just like a conventional four-stroke car engine.
In those conventional engines, the intake, compression, combustion and exhaust strokes are all performed separately. In a two-stroke engine, there is only compression and combustion, and intake/exhaust occur simultaneously with these. For their package size, two-stroke engines are generally more powerful and thermodynamically more efficient than four-stroke engines. But traditional designs are also dirty and (often) noisy.
The INNengine e-Rex has all the advantages of a two-stroke engine without the disadvantages. making it a compelling option. It can also output on one or both sides without much modification, meaning it can easily be used to drive multiple axes.
The INNengine design uses an opposed piston arrangement with four pistons on each side, for a total of eight. The opposed pistons share a combustion chamber and have a fixed rod behind it. These rods press against a plate with an oscillating, contoured design so that the rods press and release the pistons in a smooth, coordinated motion. Intake and Exhaust Like a two-stroke engine, the exhaust port precedes the intake port, so as the piston moves past the intake port, the exhaust port exits and starts creating a vacuum to allow fresh air into the next cycle. Fuel and spark are supplied the same way as any other piston engine.
This opposed-piston setup results in smooth operation with extremely low noise and vibration, while packaging keeps the overall engine size small. Additionally, variable compression can also be achieved by slightly moving one or the other end plate to control the gap between the pistons during compression. Further improve efficiency.
INNengine is showing off its e-Rex design as a working prototype for the Mazda MX-5 Miata. The engine enables the car to be all-wheel drive, and appears to take up about half the space of a conventional 1.8L engine (we’re assuming from a visual perspective). It’s also much lighter in weight. However, the 500cc e-Rex is claimed to produce 126 horsepower, matching the 1.8L’s output. INNengine did not specify the torque output, and did not respond to questions prior to publication. It’s worth noting that their test engine did have forced air. This could improve torque output, which we suspect is relatively low in such a design given the piston’s lack of leverage.
Therefore, we are not too sure about the ability of the INNengine e-Rex to be a direct drive for most automotive applications. Although that’s what the company is trying to show. However, the engine could be a very useful option as an efficient generator in a hybrid or range-extending option. INNengine, when used in an electric vehicle, could reduce battery size requirements and offer less weight and better long-distance driving options, especially if it could run as a multi-fuel option, which INNengine says it has the capability to do. Given that the battery is (and likely will be in the long run) the heaviest and most expensive part of an electric car, this could be a boon.
Considering that battery-electric models of a vehicle are typically 30% (or more) heavier than standard gasoline-burning models, this engine option could provide a means of mitigating the associated safety and road wear risks by downsizing the batteries in favor of efficient combustion generators . Given that most people drive an average of 30-40 miles (48-64 km) per day, the weight reduction not only extends the range of the vehicle’s batteries, but also allows the vehicle to use combustion only when the vehicle is in motion. Go further than normal. And it would make the cars safer, since crash tests have shown that heavier vehicles mean more injuries to people in other vehicles in crashes, a problem that’s unlikely to go away anytime soon.
The INNengine e-Rex is an interesting innovation that could find applications in the automotive sector. It is also ripe for use in other areas such as marine and off-grid power generation. Some questions about its capabilities remain unanswered, but it’s one of the most interesting designs we’ve seen in a while.
source: INN engine