Engine

From Trackpedia

Contents 1 Air Filters 2 Air Intake Systems 2.1 Normally Aspirated 2.2 Turbocharged 2.3 Supercharged 3 Carburetors 4 Fuel Injection/Injectors 5 Spark Plugs 6 Exhaust Systems 7 Drivetrains 7.1 Front-wheel drive 7.2 Rear-wheel drive 7.3 All-wheel drive

Air Filters

Air filters come in all sorts of different shapes and sizes and are there to prevent potentially damaging particles entering the engine. Smaller holes in the filter protect the engine better, but also restrict air flow. Clever design can improve the passage of air without compromising the engine, so at the very least you should replace the standard air filter with a higher performance version. Many filter upgrades are disposable so you'll need to stock up on a few for when you next service your car, some are reusable but will need cleaning periodically – make sure you follow the instructions to get the most out of your purchase.

Air Intake Systems

Changing the amount of air intake is going to yield the most dramatic results in increasing horsepower.

Normally Aspirated

The way to increase natural air flow is by improving the pipe construction transfering the air to the engine. Fluid dynamics is an fascinating science, but also fairly inaccessible to most people. To sum up in a sentence, gas flows better in specially designed pipes. Think of the transition when pouring a bottle of water from the glug glug action to the nice fast flowing stream, this is what you need to achieve with the air going into the engine. Even with your nice new air filter fitted, you'll still be limited by the inlet pipe design. In a Porsche you can be certain they've fitted the best possible turbulence free solution, but in bargain racers you can probably improve on the stock pipes. The major air filter companies such as K&N and Pipercross do a variety of 'induction kits' and if you dig around you can probably find one which is suitable for your car. These will consist of an air filter, and all the necessary pipes and fittings to get the air into the engine as fast and smoothly as possible.

Turbocharged

Unlike natural induction of airflow, a turbocharger is a device which forces air into the engine. It is, in fact, a pump, usually operated by exhaust fumes. This however means that the turbo pump will not act effectively before the engine revs increase to a point of creating enough pressure through the exhaust to activate it. At a certain moment, the turbo will burst into action. This can be improved by Anti-Lag systems and Left foot braking. A turbo must be matched to the engine type. Turbochargers also require additional cooling, hence the need to intercoolers.

The secret of increasing power via the turbo is to ensure the correct fuel to air ratios are maintained while increasing boost pressure – if you're pumping in more air you need more fuel too. At first, it's usually safest to increase the pressure by only a few PSI. The software on most modern vehicles will be able to adapt to this level of increase and deliver increased fuel to compensate. The methods involved with increasing boost pressure are varied, and you'll almost certainly need a professional to do this for you, but the technique is outlined below.

The basic boost pressure is maintained by the waste gate which is designed to open at set pressures. Adjusting the waste gate to open at higher pressures is probably the easiest method of increasing boost. If you're looking for more power, you'll need a specialist to tweak the injection settings.

Supercharged

Carburetors

Fuel Injection/Injectors

Higher flow injectors (or carburetor), and a higher flow/pressure fuel pump are generally not needed unless other engine modifications have significantly increased the potential air flow, but should follow major power modifications such as turbos, superchargers, higher compression pistons, bigger cams, etc.

Spark Plugs

Remapping or "updating" the ECU system that monitors the plugs and engine economy, can also help in improving performace. better plugs, wires, and spark coils will increase the intensity of the spark in the cylinder chamber, burning more of the fuel and generating more power.

<Ed: Please list your preferred brand, a link, and an explanation why they work well in your application>

See Also: Lubrication

Exhaust Systems

It's also important to clear out the waste generated by combustion in order to enable the engine to intake air to-fuel mixture faster. This also helps in powering up turbochargers. This is done by upgrading the exhaust. The first station is the exhaust manifold: Exhaust exits each cylinder via small pipes, and depending on the configuration of your engine these combine into one, two or more larger versions. The resulting tangle of metal pipes can make it difficult for the gas to flow smoothly and freely, and a replacing this with performance exhaust manifold will aid the flow.

An exhaust pipe needs to be matched to an equally decent manifold for it to yield the largest gains in performance. This final part of the exhaust system is designed to reduce sound and pollution (if a catalytic converter is fitted) and have a variety of filters and chambers to help achieve this. 'Cats' remove poisonous chemicals such as nitrous oxide and sulphur dioxide, mufflers deaden the noise but both sap precious power. If your conscience allows it, removing both of these elements can provide a few additional horsepower. A good 'straight through' stainless steel pipe combined with an optimized manifold can be an easy and worthwhile investment.

Having upgraded the exhaust itself, the muffler, the piping between the catalytic converter and muffler, the piping to the catalytic converter, the exhaust manifold, and the catalytic converter itself, are usually the stages best followed.

Drivetrains

The car's drivetrain, is the transsmission of power from the combustion within the engine's cylinders and unto the road. This includes: The Engine, transmission, Driveshaft, differential and driven wheels. Different cars are driven by different sets of wheels. Most modern road cars, are "Front-wheel drive" (FWD or 2WD), meaning that power is transmitted to the front wheels. Some old cars, or modern cars that are considered sporty (like most BMW's) are rear-wheel drive (RWD), where the power is going to the rear-wheels. A smaller portion is All-wheel-drive (AWD, 4WD), where all four wheels are permenantly or partially driven by the engine. Another important aspect of the drivetrain is the differential and the location of the engine. Most cars have front-mounted engines, but some have middle or rear mounted ones. This is important because, while driven wheels effect road holding, engine mounting effects car balance, together forming the car's road handling characteristics. A front engine means that transmitting power to the front wheels is easier, and that more weight is layed on them (typically 60%). Additionally, engine location generates momentum. If located in the rear, that part will actually be the one doing most of the rotation, or on the front. A mid-engine car generates a central axle around of which the chassis can be more easily and accuratly rotated. In fact, momentun usually has a more crucial effect, becuase there are other mechanical components that make up for the car's weight distribution, in order to attempt and achieve something closer to a 50:50 distribution in sports cars.

Front-wheel drive

This is the common sort of drive in a road car. It's cheaper to make and to purchase, though not usually fit for racing without being slightly modified.

• Pros:
  1. Weight distribution: The car's weight is on the front, because the whole driveline and most mass in terms of passengers are layed on the front tires, giving them more grip, especially if it's very slick. This is also good for maximizing the size of the cab.
  2. No driveshaft: The driveshaft is small, and therefore there is a siginificantly smaller lost of power, better millage, and less wear.
  3. Road handling: Due to weight distribution, a FWD will tend to understeer, which is generally safer and far more predictible in most normal driving situations, and most of the time on the track as well.
• Cons:
  1. Weight distribution: The 60% weight to the front, with even more weight due to the driver's weight, will cause a tendency of understeer, which is a frustrating aspect in driving and it can make the car prone to oversteer due to a forward weight transfer, in which case there would typically be less control than in a RWD.
  2. Power vs. Turning: The front tires are the ones carrying the car's weight, accelerating it, turning it, and are also doing most of the braking and water draining, creating more wear on the tires and a tendency of power understeer.
  3. Power vs. Weight transfer: With acceleration taking place, the car pitches forward due to a rearward weight transfer actually reducing weight to the driving wheels. This is more likely to hinder power as you get off of the line.

Rear-wheel drive

This is the common type of racing vehicles, and the ones most adventagous in advanced motoring. Typically, a front or mid-mounted engine is better. A. Front-Engine:

• Pros:
  1. Good weight distribution: This setup enables for better, more even weight distribution.
  2. Good weight transfer: As you accelerate, weight shifts backwards, giving more grip to the rear tires. Unless accelerating hard or/and on slippery terrain, you will get less wheelspin.
  3. Good road handling: While FWD's are always front-engine, creating a tendency of understeer, front Engine RWD allows for a small amount of understeer due to momentum, while still being able to keep "pure" steerability and tendency of oversteer that can help in sharp cornering. The best handling is a small amount of initial understeer, followed by controlled oversteer.
• Cons:
  1. Driveshaft: The nessecary long driveshaft transffering power to a rear differential will result in great lost of power, and typically more wear. This can be minimized with modern technology, but there's still a problem in trassmitting power in straights.

B. Rear-Engine:

• Pros:
  1. Weight distribution: Gives more grip to the rear tires, decreasing the chance of wheelspin.
  2. No driveshaft: Like in a FWD, no decrease of power due to a short driveshaft. This also offers better millage and minimal wear.
• Cons:
  1. High rear momentum: With the engine being placed behind, the momentum is working on the rear of the car. This hinders car stability, which is usually more important than sheer grip. It will result in a tendency of Oversteer when braking or lifting-off, even in a straight. Oversteer will typically be sharp and hard to control, but can be controlled with more throttle, allowing for an improved ability to reach neutral handling around a corner.

C. Mid-Engine:

• Pros:
  1. Weight distribution: Being typically far closer to a 50:50 weight distribution, these cars corner better and under more control.
  2. Momentum: Being low on moment, allows the mid-engine car to be even more easily tamed than a Front-engine RWD with similar weight distribution.
• Cons:
  1. Driveshaft: A short but existant driveshaft results in some wear, slight increase in millage and reduction of power. This, however, is not going to yield crucial differences to a FWD or front mounted AWD.

All-wheel drive

A. Front Engine

• Pros:
  1. Increased overall adhesion: Having all four wheels under power, allows for twice adhesion and traction. This is important on slippery conditions (rallying), high speeds (straights) and while getting off of the line.
  2. Road handling: With weight shifting backwards, but power being better transmitted to the front, it is possible to make an AWD car quite balanced, allowing to reach and sustain neutral handling better than in any other car. It will initialy tend to slight understeer, which is good as a basic safety feature. Beyond that point, the driver can induce a very predictible and controlled oversteer and immediatly mesh the power to drag the car with all four tires sliding.

• Cons:
  1. Road handling: Allowing all four tires to transmit power might not always be the best idea. This puts extra demands on the front tires, which are (in a RWD) completly free to steer the car. This results in understeer. A bit of initial understeer is important, but beyond that point it is a problematic aspect in driving.
  2. Mechanical wear: Two or three differentials, a rear driveshaft and twice the demands of acceleration, requires more fuel consumption, less-than-optimal transmission of power, and great wear. This is less common in modern cars that are constantly driven by all four wheels (unlike "4 by 4").

B. Mid Engine:

• 'Pros:
  1. Road handling: In theory, this might supply the ultimate road handling. Being stabilized in terms of weight distribution, momentum, and power distribution, it is a good setup, allowing for very predictible driving, slight initial understeer followed by controlled four-wheel sliding. This is sometimes combined with four-wheel steering to give it extra manouverability.
• Cons:
  1. Mechanical wear: By requiring two driveshafts and three differentials, there is a lost of power and increased wear and fuel consumption.

C. Rear Engine:

• Pros:
  1. Weight transfer: Due to increased transmission of power while still applying power to the front wheels, this is the fastest car for getting off of the line or for acceleration in general. It is not likely to achieve that crucial an effect, though.
  2. No understeer: The increased grip with the momentum and power working directly on the rear, allows for no understeer.
• Cons:
  1. Rear momentum: With the inertia working on the back of the car, it is far less stable and less easy or safe to manouver and control through corners.
  2. Mechanical wear: In spite of having just one driveshaft, unlike the mid-engine design, transfering power forward by a long driveshaft will result in extensive wear, not only to the driveshaft, but also to the front tires and splines.

References:

Driving Techniques and Car Control - Drivingfast.net