Any car that you buy today from a normal automobile manufacturer has a number of compromises built into it. These compromises are caused by several factors:
- The attempt to fit the car into a certain price range
- The need to meet emissions standards
- The desire to provide maximum life and reliability
These compromises often give you lots of room for improvement in terms of performance! There are many different ways to create more horsepower from a stock engine. Here are several examples (generally in order from least to most difficult/expensive):
Change your computer chip. Sometimes, but certainly not always, you can change a car's performance by changing the ROM chip in the engine control unit (ECU). You usually buy these chips from aftermarket performance dealers. It is valuable to read an independent review of the chip you are contemplating, because some chips are all hype and no performance.
Let air come in more easily. As a piston moves down in the intake stroke, air resistance can rob power from the engine. Some newer cars are using polished intake manifolds to eliminate air resistance there. Bigger air filters and reduced intake piping can also improve air flow.
Let exhaust exit more easily. If air resistance or back-pressure makes it hard for exhaust to exit a cylinder, it robs the engine of power. If the exhaust pipe is too small or the muffler has a lot of air resistance then this can cause back-pressure. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system.
Change the heads and cams. Many stock engines have one intake valve and one exhaust valve. Buying a new head that has four valves per cylinder will dramatically improve airflow in and out of the engine and this can improve power. Using performance cams can also make a big difference.