This Volkswagen, converted to hydrogen by a Brigham Young University team headed by Roger Billings, won first place for emissions in the “Urban Vehicle Design Competition” at the General Motors Proving Grounds in Ann Arbor, MI.

The Contest marked a milestone in eliminating nitrogen oxide from the exhaust. As reported by the press, “The air that comes out of the engine is cleaner than the air that goes in.”

The ‘Clean Car’ — This Engine Might Stall in L.A. Air — An automobile engine that reportedly cleans the air as it operates was demonstrated at Brigham Young University by its student inventor.
– Los Angeles Times
May 20, 1972