Get ready to have your mind blown: the INNengine E-REX claims to revolutionize the engine world with its so-called '1Stroke' technology. But here's the kicker—it's not actually a one-stroke engine. Confused? Don't worry, we'll break it all down for you. From its quirky design to its bold claims, this tiny powerhouse is anything but ordinary. And this is the part most people miss—it’s not just about the strokes; it’s about challenging everything we thought we knew about engines.
You’ve seen your fair share of oddball engines here on Jalopnik, from the bizarre Trojan two-stroke cube with its wishbone-shaped connecting rods to the triangular Napier Deltic diesel. But the INNengine E-REX? It’s in a league of its own. Based in Granada, Spain, INNengine has crafted two pint-sized marvels: the E-REX and the Rex-B. Inside the E-REX, you’ll find a setup reminiscent of the Napier Deltic—eight pistons crammed into four cylinders. These pistons move toward each other to compress the air-fuel mixture and then move apart to reveal ports in the cylinder walls for intake and exhaust. Sound like a two-stroke? You’re not wrong, but there’s more to the story.
Here’s where it gets really interesting: each set of pistons sits on a spinning disk that resembles the undulating floor of a Tilt-A-Whirl. Car and Driver legend Csaba Csere calls this a 'thrust plate,' and we’ll stick with that. The E-REX uses two of these plates for its dual piston sets, while the Rex-B opts for a single plate and a single set of four pistons in four fixed-head cylinders.
Now, let’s tackle the controversial '1Stroke' claim. Despite the name, the E-REX isn’t a true one-stroke engine. It handles combustion and exhaust in one stroke and intake and compression in the next—that’s two strokes, not one. So why the misleading name? INNengine wants to distance itself from the stigma of traditional two-strokes, which are notorious for burning oil alongside fuel. The E-REX and Rex-B? They don’t do that. But is this just clever marketing, or a genuine innovation?
One of the E-REX’s standout features is its balance. Thanks to its opposing pistons, the engine vibrates so little that INNengine performed a coin test—just like Rolls-Royce does with its V12s. The result? The coin barely moved. Meanwhile, a cup of water placed on a conventional engine shook like a T-Rex was on the prowl. And here’s another cool trick: the two thrust plates can move out of phase with each other, allowing the engine to adjust compression ratios on the fly. Think of it as a simpler, more reliable alternative to Nissan’s variable compression engine, which has had its fair share of recalls.
At just 500 cubic centimeters and 85 pounds, the E-REX is tiny—though INNengine is already working on a 700cc version. Despite its size, the company claims it produces 120 horsepower on atmospheric pressure. To test this, they dropped an E-REX into a Mazda Miata, and the results sound promising. But here’s where it gets controversial: some commenters insist there’s a supercharger in the mix, making the 120 hp claim seem dubious. Not so fast. As a two-stroke, the E-REX likely uses the supercharger for scavenging—a process that helps clear out exhaust gases and bring in fresh air for the next combustion cycle. It’s not about adding power; it’s about helping the engine breathe efficiently, just like in Detroit Diesel’s 71-series engines.
INNengine also simplifies things by ditching traditional valve trains and the downsides of direct injection. With no valves, there’s no buildup of deposits, a common issue in direct-injection engines. And unlike typical two-strokes, there’s no exhaust port lid to worry about—the pistons handle all the port opening and closing.
While the Miata test was fun, INNengine sees the E-REX more as a range-extender for electric vehicles, essentially acting as a battery charger. The company claims it matches four-stroke engines in emissions and efficiency while packing the power density of a two-stroke. Plus, its variable compression allows it to adapt to different fuels, making it a versatile contender.
So, what about that '1Stroke' label? A true one-stroke engine would need to complete all four cycles—intake, compression, combustion, and exhaust—in a single stroke. That’s 180 degrees of crankshaft rotation. While AMPERe’s prototype one-stroke engines come close with a secondary combustion chamber, the E-REX doesn’t follow that path. Calling it a '1Stroke' is more of a pragmatic marketing choice, similar to how racing series classify Mazda’s 1.3-liter rotary engine as a 2.6-liter.
But here’s the big question: Is the E-REX a game-changer, or just another clever gimmick? Let us know what you think in the comments. Could this tiny engine redefine efficiency and power, or is it just another footnote in automotive history? The debate is open—and we can’t wait to hear your take.
