German media proposes theory on Mercedes and Red Bull's alleged 2026 engine loophole

A new, unconfirmed theory from German media attempts to explain the alleged technical loophole that Mercedes and Red Bull are suspected of exploiting regarding the 2026 power unit compression ratio. The report suggests a complex method involving differential thermal expansion and a small, valve-like chamber to effectively increase the compression ratio on track beyond the regulated static test limit, a claim Mercedes team principal Toto Wolff has vehemently denied as his team insists its design is fully legal.

Why it matters:

The controversy strikes at the heart of Formula 1's new 2026 technical era, where a significant reduction in the allowed compression ratio from 18:1 to 16:1 was a key regulatory change. If top teams have found a way to legally circumvent this intent, it could create a major performance disparity from the very first race of the new regulations, undermining the FIA's goal of closing the competitive gap and controlling costs.

The Details:

• The core of the alleged loophole centers on the difference between a static, cold test in the garage and dynamic, hot conditions on track. Teams are suspected of designing systems that show a compliant 16:1 ratio during official FIA checks but allow a higher, more powerful ratio during actual racing.
• The Proposed Mechanism: Auto Motor und Sport theorizes Mercedes uses 3D-printed pistons designed to expand uniquely under heat, initially raising the compression ratio to around 17:1.
• A Second Stage: The report further suggests a tiny, one-cubic-centimeter chamber is connected to the main combustion chamber via a narrow channel near the pre-chamber spark plug.
  • In a static test, this chamber fills normally, contributing to the total combustion volume and keeping the calculated ratio at 16:1.
  • The theory posits that at high operating temperatures and pressures, the system is designed so this small volume does not expand into the narrow channel during compression. This effectively reduces the active combustion volume, thereby increasing the compression ratio further during on-track operation.
• Red Bull's Position: The same German report claims Red Bull's power unit division, Red Bull Powertrains, has also identified this potential but has not yet developed a reliable implementation.

What's next:

The FIA has been actively engaged with teams to clarify the situation and is expected to formalize a definitive test procedure to close any perceived regulatory ambiguity.

• Toto Wolff's forceful defense indicates Mercedes will not back down, setting the stage for potential technical debates or even protests if the performance delta appears on track in 2026.
• The outcome will set a crucial precedent for how the 2026 power unit regulations, a cornerstone of F1's next era, are interpreted and enforced, with all manufacturers racing to finalize their designs under a now-intensified spotlight.

summary: A German media report outlines a theoretical method by which Mercedes and Red Bull could exploit a 2026 engine regulation loophole, using thermal expansion and a micro-chamber to increase compression ratio on track. Mercedes insists its design is legal as the FIA works to clarify testing procedures.