Colapinto finds himself at the center of Formula 1’s latest storm as Mercedes’ new power unit pushes the 2026 compression limit to the edge. While tests show it complies at room temperature, rivals claim it nears 18:1 when hot — potentially unlocking 12 extra horsepower per lap.
Didn't expect to be searching for articles online about engine compression a few months ago? Well, the new F1 regulations mean you have to. Luckily, we're here to break it down for you.
Before we get into the controversy surrounding Mercedes and Red Bull engines, let's do a basic review of what exactly compression ratio is. In simple terms, it is the ratio between the largest and smallest volumes that can be found in a cylinder (current F1 engines are V6, meaning they have six cylinders).
When the piston reaches the bottom of the cylinder, the maximum volume is obtained, while at the top of the stroke the volume is at its minimum. The compression ratio is simply the quotient between these two values. The higher the ratio (in F1, for example, 18:1 is compared to 16:1), the more the air and fuel mixture is compressed inside the cylinder, reducing it to a fraction of its original volume.
This allows more power to be extracted at the moment of ignition, i.e., higher performance is obtained from the same amount of fuel. And in a sport where the goal is to gain power, this difference is fundamental. Under the previous regulations, a compression ratio of 18:1 was allowed. However, the new rules that will come into force in 2026 impose a limit of 16:1.
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Regulatory measurements are taken at “ambient temperature,” i.e., when the engine is cool and parked in the garage. However, the ingenious teams at Mercedes—and to a lesser extent Red Bull—have managed to get their new engines to operate at a compression ratio of close to 18:1 when they are hot and in full competition, without violating the ambient temperature tests. This difference could theoretically translate into an additional 12 horsepower or an approximate improvement of a quarter of a second per lap, an advantage that cannot be overlooked.
Mercedes argues that its system is completely legal, as it passes all the tests set out in the regulations, and the FIA has confirmed that it complies with the letter of the law. Meanwhile, other manufacturers are not so impressed. In fact, the fact that Red Bull has not been able to successfully replicate the Silver Arrows' solution has led Honda, Ferrari, and Audi to take a stand against it, forming a decisive voting bloc if the matter is put to a vote.
The FIA has made it clear that it wants to resolve this controversy before the first race, which will be held in Melbourne. The official statement on the legality of the Mercedes engine hinted that “if necessary, adjustments to the regulations or measurement procedures may be considered in the future.” It is most likely that the system will be considered legal for this year while changes are studied to limit this practice from the 2027 season onwards, as the time to implement modifications before Melbourne is very tight.
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