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Many factors come together in any car in order to determine the effective horsepower of the vehicle. Part of this comes from the basic construction of the car as well as the internal systems and computer controls that are in place. Many components cannot be modified or provide no consistent increase in horsepower. Some other parts of a vehicle can be changed in order to make the engine more efficient so that the car can achieve a measurable speed improvement when racing. Drivers will want to explore several popular options when attempting to increase horsepower and speed.

A major contributing factor to the amount of horsepower that a car generates is the volume of air flowing moving through the system. It must enter the car and the engine efficiently, move through the cylinders and then out through the exhaust with the minimal amount of resistance in order to achieve the best horsepower possible. Changing the exhaust system on a vehicle will help to move air away from the engine efficiently. A restrictive exhaust will force the engine to waste energy pushing the air out through the muffler. A simple solution is to use a more open exhaust with larger pipes. Another option is to install a dual-exhaust.

One of the most fundamental and effective ways to increase engine horsepower is to modify or change the cylinder heads. The heads are what regulate the flow of air into the cylinders where combustion occurs. Cylinder head porting involves changing the shape and size of the channels in the head. These precise changes will force more air into the engine more efficiently. Alternately, some drivers seek out older cylinder head castings that have superior properties when compared to certain modern castings. A vehicle can see an increase of 10 to 40 horsepower using these methods depending on other factors. Racing enthusiasts often turn to porting because it does not modify the external appearance of the engine.

Turbochargers are not an option for all cars. A turbocharger is a device that compresses the air coming into an engine. The compressed air is pushed into the cylinders. This increases the amount of air in the cylinder. The combustion that occurs provides more power and is very efficient. Turbochargers and superchargers require extensive modifications and can be a costly way to increase horsepower. They also change the appearance of the engine in a way that cannot be hidden. This could cause some cars to be disqualified from races that do not permit turbochargers. Drivers might also have problems passing annual inspections since turbochargers are forbidden in certain municipalities on regular roads. They can also change emissions readings during an inspection.