The compression ratio has once again become a hot topic in Formula 1, and of course it cannot be discussed without mentioning the Mercedes engine. Central to numerous winter rumors, the Brackley-based team was believed to have found a way to increase the compression ratio from 16:1 to 18:1, potentially gaining around 10–15 extra horsepower, which translates to roughly two-tenths of a second per lap.
However, recent insights the German magazine Auto Motor und Sport F1 have revealed a more nuanced picture. While the compression ratio is indeed present, Mercedes had to devise a very specific trick for its engine. In recent years, compression ratios had taken a back seat, but with the new technical cycle, they have returned to the forefront. This is due to reduced fuel flow limits and the use of zero-CO₂ gasoline, which results in lower energy density.
Mercedes discovers how to bypass static checks
A higher compression ratio offers greater advantage and efficiency compared to the past. Mercedes has leveraged this, reportedly using deformable materials. Specifically, the team employed connecting rods made from austenitic steel to effectively increase compression.
This type of stainless steel has low carbon content but high chromium and nickel, which increases thermal expansion. The engine block, by contrast, uses a different alloy that expands less. As a result, the cylinder volume decreases under heat, thereby increasing the compression ratio.
Additionally, 3D-printed pistons were used to customize expansion properties. Yet, according to some experts, these materials alone cannot achieve an 18:1 compression ratio, which theoretically maxes out at around 17:1.
What happens during static testing
Mercedes reportedly needed another trick. Recent rumors suggest that the engineers may have connected a tiny pocket—just one cubic centimeter in volume—to the combustion chamber through a very narrow channel. The entry point is at the top of the cylinder, near the pre-chamber spark plug.
This setup is intended to deceive static tests. During these tests, the pocket fills as the piston moves upward. On track, however, with higher temperatures and engine speeds, a critical pressure must be reached to prevent the pocket from expanding into the narrow channel during compression. This affects the apparent increase in compression ratio—a practice strictly forbidden by the FIA, which has reportedly already closed an investigation into this matter.
Conclusion
In summary, the Mercedes engine likely did not reach an 18:1 compression ratio purely through materials alone. Additional engineering tricks could be involved, assuming such a high ratio was truly achieved. The exact details remain a closely guarded secret, but the combination of clever materials and clever engineering appears to have played a significant role in boosting performance.
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