American market cars also suffered a performance hit due to a compression ratio of 8.6:1 vs 9.2:1 for most of the rest of the world state emissions legislation which reduced horsepower.

Urban and Enduro reduce horsepower to 100 bhp and provide different levels of ABS and traction control accordingly.

The night before the race, CART officials attempted to make last-ditch efforts to curtail speeds by having the teams take downforce out of the car, and reduce horsepower.

The use of leaded gasoline began being curtailed in the early 1970s, which resulted in lower-compression engines being used, and thus reducing horsepower and performance.

US emissions regulations also reduced horsepower.

The restrictors limit air flow into the engine through the carburetor to reduce horsepower and speed.

The lower ratio would reduce horsepower, Triplett said.

Modifications reduced RPMs and horsepower, which helped engines and pieces to last longer.

Even today the MP4/3 is still considered to be one of the most powerful F1 cars ever made, since turbo boost pressure would be reduced to 2.5 bar in 1988, which reduced horsepower.

Changes to the camshafts, exhaust and intake systems reduced peak horsepower to 105bhp, while torque at lower revs was boosted to suit its less focused role.