Relatively inexpensive ways to boost a car's horsepower include running higher-octane gasoline and improving the car's intake and exhaust systems. Improving the intake systems allows the car to have a richer fuel-air mixture from the additional oxygen brought in from the new intake, while exhaust improvements allow a car to get rid of exhaust more quickly and to produce more power. Tuning a car's engine control unit can also yield power gains in many automobiles
The most common intake and exhaust modifications for improving power output in a car are a new air filter and a new muffler. Air intakes built for high performance allow more air to the engine than factory air filters and can improve output by as much as 10 horsepower in some cases; a high-flow exhaust can yield similar gains. More complex improvements include straight-flow exhaust pipes and other engine modifications, but these are usually more costly than simply changing to a high-performance air filter or muffler.
Tuning an engine by modifying its engine control unit software, a process commonly known as "chipping' the engine, can also easily boost engine output, though the amount of gain available depends on the engine. Turbocharged or supercharged engines see the greatest gains from engine control unit tuning since most factory settings use conservative boost pressure settings, but modifying the boost too high may damage the engine. Naturally aspirated motors usually see modest gains from chipping without additional modfications, however.