by Dennis Crouch
In Ethanol Boosting Systems, LLC v. Ford Motor Company, No. 2024-1381 (Fed. Cir. Dec. 23, 2025), the Federal Circuit affirmed three PTAB final written decisions holding MIT-owned patents on fuel management systems unpatentable as obvious under 35 U.S.C. § 103. Judge Chen wrote for a panel that included Judges Clevenger and Hughes. The patents claim dual-injection engine architectures designed to suppress "engine knock" through evaporative cooling from direct fuel injection. The case arrives with an unusual procedural history: the Board initially denied institution based on a district court claim construction, then granted Ford's rehearing petition fifteen months later after the Federal Circuit vacated part of that construction in an earlier appeal. EBS argued this delay was ultra vires agency action, but the court found § 314(d) bars any challenge that functionally seeks to "de-institute" an IPR proceeding. On the merits, the court rejected EBS's argument that the claims require an anti-knock agent other than gasoline, finding the specification's disclosure of a "gasoline only" embodiment precludes adding that implicit limitation into the claims.
Reading this case and the patents brought me back to my Princeton Mechanical Engineering course titled "mobile power plants." The technical subject matter here involves work by three MIT researchers attempting to address engine knock for ethanol boosted gasoline engines. Engine knock involves unburned air/fuel mixture in a cylinder that spontaneously autoignites before the spark-initiated flame front reaches it. This premature detonation creates damaging pressure waves and limits engine performance. The patents propose a solution using two fuel injection mechanisms operating in different torque regimes. At lower torque values, only the port injector operates. Knock is not a constraint in this regime because cylinder pressures and temperatures remain well below the autoignition threshold. At higher torque values, both injectors engage, with the direct injector supplying an increasing fraction of the total fuel as torque rises. The key insight here is thermodynamic: liquid fuel directly injected into the cylinder vaporizes by absorbing heat from the compressed charge, dropping the cylinder temperature in a way that avoids autoignition. The patents particularly contemplate ethanol as the directly injected fuel because ethanol's latent heat of vaporization (855 kJ/kg) is nearly three times that of gasoline (306 kJ/kg), providing substantially greater evaporative cooling.