Performance tuning is the tuning of an engine to increase the power output, torque, and responsiveness of the engine as well as the reliability and economy. To performance tune the engine, it must be strong enough to endure the extra power, sometimes far stronger than the standard engine. Also when Performance Tuning the car you must take into account the transmission, suspension and the brakes to make sure that these match the power output and torque of the engine as this will affect the overall performance of the car and make it more reliable and competitive. Most people want to increase the power output of an engine. The main way that is used to do this is to increase the rate and efficiency of combustion in an 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.
• 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 air boxes 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).
• Optimizing 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 oxidizer 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.
• Manufacturer Detuned Engines - Changing the tuning characteristics electronically, by changing the firmware of the engine management system (EMS). This chip tuning also works because many manufacturers produce one engine which is used in a range of models and the power and torque characteristics are determined solely by the engine management system software. This allows the manufacturers to sell cars in various markets with different tax and emissions regulations without the huge development cost of designing different engines. Cross platform engine sharing also allows for a single engine to be used by different brands, tuned to suit their particular market.
Hi My name is Mitchel and I have been in the Automotive industry since 1991 having built my own performance cars during this time but I will go into more detail about this in my future articles!
