Car tuning is both an industry and a popular hobby, in which a car is modified in order to improve its performance and handling and better suit the owners driving style. As most cars leave the factory set up for average driver expectations and average conditions, Car engine tuning has become a way to personalize the characteristics of the vehicle to the owners preference. For example cars may be altered to provide better fuel economy, produce more power at high RPM or the ride comfort may be sacrificed to provide better handling. See also our helpful info on Engine Conversion Tuning.

Car tuning is related to auto racing, although most performance cars never compete. Rather they are built for the pleasure of owning and driving such a vehicle. Another major facet of tuning includes performance modification the car exterior. This includes changing the aerodynamic characteristics of the vehicle via side skirts, front and rear bumpers, adding spoilers, splitters, air vents and light weight wheels.

Engine tuning involves modifications designed to increase the power of the engine. These modifications can range from a simple chip tuning, to adding nitrous injection, to a complete engine swap.

So what does it mean?

"Tuning an engine" has many different meanings today. Traditionally, to actually tune an engine meant adjusting the timing and the air/fuel ratios. Today, many people consider tuning to be adding cold air intakes, exhaust systems, turbochargers, or any other part that could conceivably make the car faster. It is important to note that the two different meanings behind the word tuning refer to two completely different methods of making a car faster.

Adjusting engine timing and air/fuel ratios generally improves power and reliability of an engine without any further modifications. On the other hand, tuning an engine becomes incredibly beneficial after already heavily modifying the engine with upgrades, like forced induction (including nitrous) or adjusting the internal parts to increase engine compression.

Adding parts to increase horsepower and torque is mechanical tuning, but adding body kit or/and modify interior is optical tuning.

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In most cases, people are interested in increasing the power output of an engine. Many well tried and tested techniques have been devised to achieve this, but all essentially operate to increase the rate (and to a lesser extent efficiency) of combustion in a given engine. This is achieved by putting more fuel/air mixture into the engine, using a fuel with higher energy content, burning it more rapidly, and getting rid of the waste products more rapidly - this increases volumetric efficiency. The specific ways this is done include:

• Increasing the engine displacement. This can be done by "boring" - increasing the diameter of the cylinders and pistons, or by "stroking" - using a crankshaft with a longer stroke (in combination with pistons of shorter compression height, to maintain the original compression ratio), or both.
  Using larger or multiple carburetors, to create more fuel/air mixture to burn, and to get it into the engine more quickly. In modern engines, fuel injection is more often used, and may be modified in a similar manner. Also to keep the engine finely tuned its always good to make sure you are working with a clean unit.
  
• Increasing the size of the valves in the engine, thus decreasing the restriction in the path of the fuel/air mixture entering, and the exhaust gases leaving the cylinder. Using multiple valves per cylinder results in the same thing - it is often more practical to have several small valves than have larger single valves.
  
• Using larger bored, smoother, less contorted intake and exhaust manifolds. This helps maintain the velocity of gases. Similarly, the ports in the cylinder can be enlarged and smoothed to match. This is termed "Cylinder head porting", usually with the aid of an air flow bench for testing and verifying the efficiency of the modifications. The larger bore may extend right through the complete exhaust system, using larger diameter piping and low back pressure mufflers, and through the intake system, with larger diameter airboxes and high-flow, high-efficiency air filters. Muffler modifications will change the sound of the car's engine, usually making it louder; for some tuners this is in itself a desirable property.
  
• Increasing the valve opening height (lift), by changing the profiles of the camshaft or the lift (lever), ratio of the valve rockers (OHV engines), or cam followers (OHC engines).
  
• Optimising the valve timing to improve burning efficiency - usually this increases power at one range of operating RPM at the expense of reducing it at others. For many applications this compromise is acceptable. Again this is usually achieved by a differently profiled camshaft. See also Four-stroke cycle#Valve Timing, variable valve timing.
  
• Raising the compression ratio, which makes more efficient use of the cylinder pressure developed and leading to more rapid burning of fuel, by using larger compression height pistons or thinner head gasket, or by milling "shaving" the cylinder head.
  Forced Induction; adding a turbocharger or supercharger. The fuel/air mass entering the cylinders is increased by compressing the air first, usually mechanically.
  
• Using a fuel with higher energy content or by adding an oxidiser such as nitrous oxide.
  Changing the tuning characteristics electronically, by changing the firmware of the engine management system (EMS). This chip tuning often works because modern engines are designed to give a great deal of raw power, which is then reduced by the engine management system to make the engine operate smoothly over a wider RPM range, with low emissions. By analogy with an operational amplifier, the EMS acts as a feedback loop around an engine with a great deal of open loop gain. Many modern engines are now of this type and amenable to this form of tuning. Naturally many other design parameters are sacrificed in the pursuit of power.
  
• The choice of modification depends greatly on the degree of performance enhancement desired, budget, and the characteristics of the engine to be modified. Intake, exhaust, and chip upgrades are usually amongst the first modifications made as they are the cheapest, make reasonably general improvements (whereas a different camshaft, for instance, requires trading off performance at low engine speeds for improvements at high engine speeds), can often improve fuel economy, generally don't affect engine reliability much (because no moving parts are modified), and are in any case essential to take full advantage of any further upgrades.