ABS: See anti-lock brakes.
Airbags: These are nylon bags that, when triggered by sensors in a collision, inflate with hot nitrogen gas. Their purpose is to prevent or lessen the severity of injury when vehicle occupants are thrown about by the force of the crash. All new cars and light trucks must have two frontal bags (one in the steering wheel and one on the passenger's side of the dash). Some cars have additional ones: in the sides of the front seats; in the roof above the side windows or in the pillars so they cover the windows in a side impact (these are called curtain airbags); below the dash, to protect the front occupants' knees; and on some cars, in the sides of the rear seats. The bags explode with considerable force and, contrary to what you've seen in the movies, deflate almost immediately, so you don't sit there with your face in a pillow. (Some curtain airbags stay inflated a few seconds longer, to protect occupants in the case of rollovers.) It all happens so quickly that some people don't realize the airbag has deployed until they see it hanging out of the wheel. Their force can make them dangerous if you're not wearing your seatbelt, which holds you in the proper position for airbag deployment. NEVER allow front-seat passengers to ride with their feet on the dash; if the airbag deploys, it will do serious and possibly irreparable damage to the legs and pelvis. If your vehicle has seat-side airbags, do not use a seat cover.
All-wheel drive: In simplest terms, a vehicle with all-wheel drive has power available to all four wheels, as opposed to front-wheel drive or rear-wheel drive, where only one set of wheels has power. The problem is that automakers often use whatever term they like best, and you'll have to ask your salesperson to explain exactly what your car is meant to do. Properly, all-wheel drive -- which is sometimes called full-time all-wheel drive, or permanent four-wheel drive or full-time four-wheel drive -- determines where torque (power) is needed depending on driving conditions, and automatically distributes it either to the front or rear axle or, in some systems, to a specific wheel. (In a part-time four-wheel drive vehicle, the driver switches the system manually.) Depending on the vehicle, the all-wheel system may send some power to all wheels at all times, or the vehicle may run exclusively in front-wheel drive until the system detects wheel slippage, whereupon it sends a percentage of power to the rear wheels (auto writers sometimes call this "slip-and-grip"). All-wheel drive systems can give better traction in poor weather, although they're no substitute for safe driving. Also see Torque Distribution.
Anti-lock brakes: Often shortened to ABS. If you hold the brake pedal down, your wheels will lock up -- the brakes won't allow them to turn. On a slippery surface, this can cause the car to slide, just as a toboggan will on snow. On cars without ABS, the proper technique is to pump the brakes, which allows the tires to grip the surface while stopping. Anti-lock brakes electronically pump the brakes, and do so much faster than a driver could. Your car will not necessarily stop sooner (in some cases, such as on gravel roads, it may take slightly longer to stop), but you will be able to better control the car's movement, allowing you to possibly avoid a collision. The brake pedal will vibrate, which can cause some people to let off the pedal. If your car has ABS, try a panic stop in a safe place so you'll know what to expect. Anti-lock brakes don't do this every time you put your foot on the pedal, only when the system senses that the wheels are slipping.
Biofuel: A petroleum or diesel fuel substitute made from non-petroleum sources, such as corn, agricultural waste or cellulose. It's usually mixed with petroleum, and named to indicate the amount: E85 is 85% biofuel (ethanol, in this case) and 15% petroleum gasoline. You shouldn't put E85 biofuel into your car unless the manufacturer states that it can be used, as it can damage the system. A vehicle capable of burning biofuel is commonly called a flexible fuel vehicle, or FFV.
Bi-xenon headlamps: Xenon (pronounced ZEE-non) headlamps use xenon gas and are brighter than halogen headlamps. The "bi" means that both the regular and the high-beam headlamps are xenon, but rather than two bulbs, the system uses a shutter to block some of the light when the regular low-beam lights are used.
Body-on-frame: A type of vehicle construction that uses a metal frame, to which the engine and all driveline components are mounted, with the body bolted to the frame. Almost all vehicles used to use this type of construction. Today, almost all cars are unibody construction. Pickup trucks and some SUVs still use body-on-frame because it is heavier and stronger, and allows these vehicles to carry and tow heavy loads.
Brake Assist: Sometimes written as BA or BAS, this system measures the rate of brake pedal travel and, if it detects panic braking, will generate increased braking force. This is to compensate for the fact that many drivers don't hit the brakes hard enough in a panic situation to prevent a collision.
CID: Stands for Cubic Inch Displacement and is a measure of engine size. See Engine Size.
Crumple zones: An area of a vehicle that is designed to compress or crumple during a collision in order to absorb energy. Without a crumple zone, the crash energy is transmitted to the occupants, which increases the risk of serious injury. Crumple zones are most prominent at the front and rear of the vehicle, and can include such energy-absorbing materials as honeycomb waffle behind the bumper fascia. People often complain that new cars "just crumple up" when they're hit, but that's because they're engineered to do that in order to reduce injuries -- it's easier to replace a car than a person.
CVT: Short for Continuously Variable Transmission. This is an automatic transmission that uses a belt and pulleys instead of gears to theoretically produce an infinite number of gear ratios. Since the ratio changes constantly along with engine speed, a CVT allows the engine to always run at its optimal rpm (revolutions per minute), which results in improved fuel mileage. CVTs are generally used on smaller vehicles and on hybrids. Some also have a "manual mode", which allows a driver to sequentially "shift" the transmission to pre-set ratios.
Cylinders: Engines contain round cylinders; these are fitted with pistons, which move up and down inside the cylinders and turn a central crankshaft when the engine is running to create power. The engine is described by the number of cylinders: a "four-cylinder engine" has four cylinders, and therefore, four pistons. An inline engine has its cylinders upright or on a slant, and all in one row (most commonly four-cylinders and some six-cylinders). A V engine contains two banks of cylinders set in a V-shape with the crankshaft at the bottom of the V (most commonly V6 or V8 engines). A horizontally-opposed engine (also called a flat or boxer engine) has its cylinders and pistons laid out flat on either side of the crankshaft.
Disc brakes: A disc brake consists of a metal disc (also called a rotor) which fits behind the wheel and tire and turns along with the tire. Fitted over top of the rotor is a caliper, which contains brake pads, consisting of steel backing plates covered with friction material. When you hit your brake pad, the caliper presses the brake pad against the brake disc, which slows and finally stops it from spinning. (To understand the principle, put a pencil through the hole of a CD, spin it, and then grab the spinning CD with your fingers -- this is basically how disc brakes work.) All modern cars have disc brakes on the front wheels. Many also have disc brakes on the rear, but older or less-expensive cars will have rear drum brakes.
Drive by wire: A system which replaces mechanical actuators with electronics. Some production cars have drive-by-wire throttles (gas pedals). It is possible to make drive-by-wire steering and brake systems, but government safety regulations require that these use mechanical linkages.
Driveline: The combination of components that produce power and transmit it to the wheels, including the engine, transmission, differential and drive shafts. It's also called a powertrain, although that term is sometimes used just for the engine and transmission alone.
Drivetrain: See powertrain.
Drum brakes: This type of brake uses a metal drum that fits behind the wheel and tire and turns along with the tire. Inside the drum are two brake shoes, consisting of steel backing plates covered with friction material. When you press the brake pedal, these shoes push out and against the brake drum, which slows and finally stops the drum (and the car). All modern cars have disc brakes on their front wheels but may have drum brakes on their rear wheels; they cost less, and while they're not as good as disc brakes (they take longer to dissipate heat), they're still safe. Most antique cars have drum brakes on all four wheels.
EBD: See electronic brakeforce distribution.
Electric power steering: Conventional power steering uses an oil-filled hydraulic pump to minimize the effort needed to steer the car at lower speeds. Electric power steering uses an electric motor instead. As it is not manually run off the engine as a hydraulic pump is, it doesn't draw power directly away from the engine, and so helps to improve fuel economy; it's also more environmentally-friendly, as it does not contain oil. Some systems use a combination, with a hydraulic pump that gets its power from an electric motor. While some electric power steering systems are well-tuned and provide good steering feel, others can sometimes feel vague and artificial.
Electronic brakeforce distribution: Shortened to EBD. During hard braking, some wheels may be turning faster than others, such as when one tire hits a patch of ice. Without EBD, all four wheels receive the same amount of braking force. EBD monitors the wheels and controls the braking force at each one, maximizing the force where it's needed to bring the car to a straight halt as quickly as possible.
Electronic stability control: Shortened to ESC. It can go by other names or trademarks, such as Electronic Stability Program or ESP (Mercedes-Benz), StabiliTrak (GM), VSC (Lexus) or many others. ESC continually monitors the vehicle to detect the possibility of a skid. If necessary, it will apply braking to one or more wheels, and/or reduce engine power, to keep the car from skidding. The system will be mandatory on all cars and light trucks sold in the U.S. by 2012. It's a good system but it's not a substitute for safe driving.
Electric vehicle: Often shorted to EV, or to BEV, for battery-electric vehicle. This is a car that does not have a gasoline engine, but relies solely on an electric motor powered by an on-board battery. The car must be plugged into an outlet or charging station to charge the battery.
Engine size: Engine size refers to the engine's displacement. Engines contain pistons, which move up and down inside cylinders to produce power; the displacement is the maximum amount of space in the cylinders that can fill with air and fuel, from the point the piston is at the top of its travel to the bottom. The number is measured in litres, such as a 3.0-litre engine. In older vehicles it was measured in cubic inches, such as a "350-cubic-inch" (it's usually written 350 cid, for cubic inch displacement). Some European manufacturers also use cubic centimetres, as in a 750-cc engine. The number is the combined volume of all of the cylinders. The larger the number, the bigger (and usually more powerful) the engine: a 6.1-litre engine is bigger and more powerful than a 3.5-litre engine.
Ethanol: A biofuel made of corn or other agricultural products, used as a petroleum substitute. It's blended with gasoline, and the name indicates the strength: E85 is 85% ethanol and 15% gasoline. E85 shouldn't be used in a vehicle that isn't ethanol-compatible as it can damage the system. A vehicle capable of burning it is called a flexible fuel vehicle, or FFV. (Some gasoline companies use a very small amount of ethanol in their gasoline and will say so on the pump; it's safe to run this type of fuel in a regular engine.) Your fuel mileage will be poorer when running on a high-ethanol blend, but it produces fewer harmful emissions. It's also a renewable resource, although the jury's still out on the effect widespread production will have on food sources, land use and pollutants from fertilizers.
EV: See Electric Vehicle.
Extended-range vehicle: This is a specialized vehicle design that contains an electric motor, a storage battery, and a small gasoline engine. It is plugged into a wall outlet or charging station and runs on its battery. When the battery charge is depleted, the gasoline engine starts up to act as a generator and produce electricity to power the car. It's not the same as a conventional hybrid, which uses its gasoline engine to directly power the wheels; extended-range vehicles only use electricity for motion. The best-known version is the upcoming Chevrolet Volt.
Extended warranty: Also called a "service contract", this is additional coverage that customers can buy to pay for repairs needed beyond the vehicle's factory warranty. It's basically an insurance policy against car repairs, and whether you should buy it depends on several factors, including its cost and your level of comfort with car repairs. As with collision insurance, it's money well spent if you need it, and money wasted if you don't. If you are considering it, it's more important to know what the policy doesn't cover than what it does, and any restrictions it may have, such as pre-approval before repairs are done.
Flexible fuel vehicle (FFV): A vehicle capable of running on E85, a blend of 85% ethanol and 15% gasoline. Vehicles not rated as FFVs should not use E85, as the fuel can damage seals and the fuel pump in conventional systems.
Four-wheel drive: Also written 4WD. In simplest terms, a vehicle capable of sending engine power (torque) to all four wheels. Automakers often use the terms four-wheel drive and all-wheel drive interchangeably, so make sure you know what your vehicle has. Full-time 4WD (also called permanent 4WD) is a system that automatically determines when and where to distribute torque for the best possible traction. Part-time 4WD is selected by the driver, using a dial or lever, to switch the vehicle from two-wheel drive (2WD) to 4WD. Now here's where it can get really confusing. Some vehicles allow the driver to switch from 2WD into full-time 4WD, while other ones allow the driver to switch from 2WD into part-time 4WD. Full-time 4WD uses a system that allows the wheels to move at different speeds, and so it can be driven on any surface. Part-time 4WD locks the front and rear axles together, and so all four wheels move at the same speed. Part-time systems should only be used on loose surfaces, such as gravel or deep snow. If you drive a vehicle locked into this type of 4WD on a dry road, the system can bind, which can cause serious damage to the vehicle. Some companies, such as Jeep, can offer the same vehicle with a choice of either full- or part-time 4WD, so be sure you know what type of system you're buying.
Front-wheel drive: Engine power is transmitted to the front wheels, which "pull" the car along. It's one of three configurations, along with rear-wheel drive and all-wheel (or four-wheel) drive.
Full hybrid: See hybrid.
Hemi: An engine with hemispherically-shaped combustion chambers (the area of the engine where a mixture of fuel and air is burned to start the process of producing power). The shape allows for unobstructed movement of the air. The term is now a Chrysler trademark, although other companies have used similar designs.
HID: Stands for High Intensity Discharge headlamps. See Xenon Headlamps.
Horsepower: A measurement of engine power. The number is given as the maximum amount of horsepower the engine can make, and the engine speed (see rpm) at which it's produced. So if an engine is rated at 250 hp @ 4000 rpm, it means that the engine's maximum horsepower is 250, and the crankshaft must be spinning at 4,000 revolutions per minute to achieve it. The term horsepower, coined by James Watt (the steam engine guy whose name is also on the light bulbs), is a measure of work done over time: one horsepower equals lifting 33,000 pounds one foot in the space of one minute. Engines are also rated by their torque.
Hybrid: A vehicle with a relatively small gasoline (or diesel) engine, an electric motor and a battery pack that work in combination to improve fuel economy. A mild hybrid uses the electric motor to assist the gasoline engine on acceleration, and shuts off the gasoline engine at idle, such as when stopped at a light. A full hybrid (also called a two-mode hybrid) does the same, but is also capable of driving the car under certain conditions solely on electric power. Hybrid vehicles recharge their own batteries while driving and are not plugged in to recharge, although cars that are, called plug-in hybrids (PHEV), are under development.
LATCH: Stands for Lower Anchors and Tethers for CHildren. Also known as ISOFIX, LUAS (Lower Universal Anchorage System) or CANFIX, it's a system built into the vehicle that allows attachment of a child seat without using a seatbelt.
Mild hybrid: See hybrid.
Monroney label: The official name for the price label required by law to be stuck on a new vehicle's window by the manufacturer, containing the suggested retail price, list of options and fuel mileage. It's named for "Mike" Monroney, the U.S. senator who originally sponsored the bill that led to its requirement.
MSRP: Manufacturer's Suggested Retail Price. The base price set by the automaker, although dealerships may charge less (or sometimes more).
Naturally aspirated engine: An engine that does not have a turbocharger or a supercharger, devices which pump extra air into the engine.
Oversteer: A potentially dangerous situation where the rear wheels are going further out in a curve than the front wheels. This can cause the back end to come around, and the vehicle will spin. There are a number of causes, including driving too fast for road conditions, and worn or inappropriate tires. Most drivers instinctively slam on the brakes, which can make it worse. Getting safely out of an oversteer can include manoeuvres that aren't necessarily intuitive, such as accelerating slightly and steering into the skid. Lessons at a winter driving school or "skid school" should be part of every driver's training. See also understeer.
Paddle shifters: Many new cars offer automatic transmissions that can be manually "shifted" for a more sporty feel. This is mostly done by moving the shifter lever, but some also offer paddles on the wheel that allow you to change the gears by pushing or pulling the paddles. You'll often see them called "F1 style" because they originated with race cars. These types of transmissions don't have a clutch pedal and don't require that you shift them if you prefer to just leave the car in "Drive".
Pillars: The roof supports. They are indicated by letters: the A pillar is at the front and holds the windshield; the B pillar is in the centre of the car; and the C pillar is at the rear and holds the back window. A car that does not have a B pillar is called a hardtop: when all the windows are open, there are no obstructions from the front door to the rear one.
Plug-in hybrid-electric vehicle: Often shortened to PHEV. This is similar to a conventional hybrid-electric vehicle that is powered by both a gasoline engine and an electric motor, but can be plugged into a wall outlet or charging station to recharge the battery if desired. While plugging in isn't required - like a conventional hybrid, the vehicle will recharge its own battery while driving - charging the battery externally increases the amount of time it can run on its battery alone, and reduces the vehicle's overall gasoline consumption. These vehicles are not on the market yet, but are coming.
Powertrain: The components that produce and transmit power, including the engine and transmission. Some people use powertrain to include the differentials and driveshafts that further transmit power to the wheels. Others use powertrain for the engine and transmission only, and use the term driveline when including other components. Another common name for the powertrain is drivetrain.
Rear-wheel drive: Engine power is transmitted to the rear wheels, which "push" the car forward. It's one of three configurations, along with front-wheel drive and all-wheel (or four-wheel) drive.
Recall: This is a notice that an automaker has discovered a potential problem with its vehicles and will repair them. Most recalls are related to safety issues and are registered in Canada with Transport Canada, or in the U.S. with the National Highway Traffic Safety Administration (NHTSA). Having a recall on your vehicle does not necessarily mean that it is unsafe; often, the automaker finds that specific parts may fail, and so it repairs all vehicles that were built with that particular batch of parts. All recalls must be performed at no charge to the customer. A recall is not the same as a technical service bulletin.
Redline: See RPM for an explanation of revolutions per minute. Each engine has a limit to how fast its pistons can move and crankshaft can turn (its rpm) before it damages itself. This rpm number is known as the redline, from the practice of automakers putting a red line on the tachometer to indicate a dangerous engine speed. Automatic transmissions will usually shift to a gear that brings down engine speed before it gets too high; redline is more of a possibility with manual transmissions, where a driver has to pay attention to keeping the car in the right gear for the engine speed. Most modern cars have an electronic failsafe that shuts off the fuel if the rpms go into the redline, to prevent engine damage.
RPM: Short for revolutions per minute, this is a measurement of engine speed. When an engine is running, pistons move up and down and so turn a central crankshaft, which eventually provides the turning power at the wheels. (The system is similar to a bicycle, if you picture your legs as the pistons.) RPM measures how many times the crankshaft turns (completes a revolution) within one minute. If your tachometer reads 3,000 rpm, this means that the crankshaft is spinning 3,000 times per minute. Also see Redline.
Run-flat tires: These tires have a very stiff sidewall that will allow you to drive on them in an emergency when they lose air. They're used in place of putting a spare tire in the trunk, which saves vehicle weight and can increase cargo capacity. The drawback is that, because of the stiff sidewall, the ride is harsher than with a regular tire; they also tend to be more expensive than conventional tires. The vehicle must also have a tire pressure monitoring system (TPMS), because run-flat tires don't look any different when they're low on air.
Service contract: See extended warranty.
Supercharger: Engines run on a mixture of gasoline vapour and air. A supercharger (also known as a "blower") is a compressor that forces extra air into the engine. This allows the engine to burn more fuel, which creates more power, which can result in a smaller engine producing the equivalent power of a larger engine. Turbochargers work on the same principle, but while turbochargers are powered by exhaust gases, superchargers run directly off the engine, using belts or gears. Turbochargers can have a slight lag between the time that you hit the throttle and the power kicks in, while superchargers produce immediate power.
Technical service bulletin: Often shortened to TSB. This is a document distributed by the automaker to its authorized dealers, informing technicians of known problems and how to fix them -- for example, if a vehicle comes into the shop making a specific noise, the TSB tells the technician what is most likely causing the problem, which saves diagnostic time. The repair may be covered under the vehicle's warranty, depending on the problem and the vehicle's warranty coverage, but a TSB is not a warranty itself.
Throttle: Another name for the accelerator pedal. Calling it the "gas pedal" isn't technically correct, because pressing the pedal directly increases the flow of air, not gasoline. Engines don't run on liquid gasoline, but rather, on a mixture of air and gasoline vapour. When you push the pedal, airflow increases, which also increases the amount of gasoline introduced into the system.
Timing belt/timing chain: Engines contain pistons, which move up and down and so turn a central crankshaft, which ultimately provides the power to turn the wheels (think of it as a bicycle, with your legs as the pistons). The pistons move when gasoline vapour ignites and the power of the explosion forces them downward. The fuel is fed into the engine, and the exhaust is removed, through valves, which are operated by camshafts. The valves must open and close at precise intervals to match the travel of the pistons -- if they don't, the car will run badly or not start at all. A timing belt or timing chain connects the crankshaft with the camshaft (each engine has one crankshaft, and one, two or four camshafts). As the crankshaft turns, the belt or chain turns, which then turns the camshaft(s) at precisely the right speed. Timing belts are lighter, quieter and cheaper than metal timing chains, but they eventually wear out and can break. If this happens, the engine won't start, and on some engines, it may cause very serious damage, which is why timing belts should be changed at regular intervals as part of the vehicle's maintenance. Be sure you know which type is on your engine. (Note: you can't see the timing belt or chain by looking at the engine, as it's behind a metal cover. The belt you can see is the serpentine belt, which operates such devices as the air conditioning compressor, water pump and alternator.)
Tire pressure monitoring system: Often shortened to TPMS, this system monitors the air pressure in the tires. Depending on the system, it will either flash a warning if a tire is low, or will provide a continuous readout of the pressure in each tire. There are two types: direct systems, which are more common, have sensors inside the tire, either as part of the valve stem, or strapped to the wheel itself, while indirect systems use exterior sensors. Direct systems must indicate when a tire is 25% below the preset recommended pressure, while indirect systems indicate at 35%. These systems are useful but should not be considered a substitute for regularly checking tire pressure, as tires can still be too low for safety and fuel economy, but not be at the 25% warning threshold.
Torque: Torque is a force that causes something to turn. In the case of an automobile, it's the power that turns the shafts that turns the wheels. It's measured in foot-pounds, and the number given is the engine's maximum torque and the engine speed (see rpm) at which it's produced. So if a manufacturer tells you a car makes 260 lb-ft @ 6000 rpm, it means that the maximum power to the wheels is produced when the crankshaft is turning 6,000 times per minute. Low-end torque is maximum power that's produced at lower rpms -- the power that pushes you back in your seat when you accelerate hard from a light, or a truck's ability to move a heavy load easily from standstill. As the engine speed rises, torque falls off and horsepower produces higher-speed power. Here's a way to think of it: you've got a rusty screw and a power screwdriver. Initially, the screwdriver has to create a lot of low-speed turning power (torque) to loosen the screw and get it spinning. As the screw loosens, the screwdriver turns faster and the screw spins faster with it.
Torque Distribution: On vehicles with four-wheel or all-wheel drive, a percentage of engine power (torque) can be distributed to either the front or rear wheels (or on some vehicles, to one specific wheel). Torque distribution is a measure of how much power can be transferred. For example, let's say we have a car that normally runs 35/65 but can distibute up to 50/50. This means that, under normal driving conditions, the front wheels are receiving 35% of the available power, and the rear wheels are receiving 65% (the numbers always add up to 100%). Should this particular system detect slippage, it can transfer as much as 50% to the front and 50% to the rear, or any combination between 35/65 and 50/50, to prevent slipping. If the numbers are 100/0 and 80/20, this means the car normally runs as a front-wheel drive vehicle, but if it detects slippage, it can send up to 20% of its torque to the rear wheels.
Torque steer: A tendency for a front-wheel-drive car to pull to one side on acceleration. It's the result of the shafts that come out of the transaxle and transmit power (torque) to the front wheels being two different lengths (because the transaxle doesn't sit precisely in the middle) and one shaft spinning one wheel slightly faster than the other. Most manufacturers have engineered their vehicles to reduce torque steer, although it can still be a problem with some high-powered front-wheel-drive vehicles. Rear-wheel-drive cars don't exhibit torque steer because there's no power going to their front wheels.
TPMS: See Tire pressure monitoring system.
Traction Control: A spinning tire has little or no traction. Modern traction control will electronically monitor the wheel, and apply the brakes and/or reduce the engine power to stop the wheel from spinning. Most cars will allow you to temporarily disable the system, as there are a few situations where you want the wheel to spin, such as when you're stuck in deep snow. Traction control is part of electronic stability control, but some vehicles are available with traction control alone. Another type of traction control is the limited slip differential, which transfers power from the wheel that's spinning to the one that has traction.
TSB: See technical service bulletin.
Turbocharger: Often shortened to turbo. A turbocharger uses a turbine and compressor to force extra air into the engine, which allows it to burn more fuel and so produce more power. With a turbocharger, a small engine can produce power equivalent to that of a larger engine. Turbocharged engines burn more fuel than a regular engine (also called a naturally-aspirated engine, meaning the air isn't forced into it as with a turbocharger) but depending on the engine, the overall fuel economy could be equivalent to or even better than a larger engine that produces the same amount of power. Because the turbine spins using exhaust gas, there can be a short period of time between the moment you hit the accelerator and the turbocharger begins to pump air and the resulting engine power increase. This is called turbo lag. Most modern systems are engineered to reduce turbo lag to a minimum. Compressing the air also heats it, which can reduce efficiency, so some turbocharged cars also include an intercooler, which cools the air to improve performance. Another form of forced air induction is supercharging, which uses the same principle as a turbocharger but runs directly off the engine, so there's no lag.
Two-mode hybrid: See hybrid.
Understeer: The tendency of a vehicle to take a wider radius than the driver intends on a curve -- you turn the wheel, but the car wants to keep going in a straight line, and so you take the curve wider than you wanted. Although it doesn't sound like it would work, the trick is to unwind the wheel: if you're turning right, bring the wheel back slightly to the left, while letting off the throttle. This will straighten the car out and help you regain control. Understeer can also mean you're taking a curve too fast, or that your tires are worn and can't grip the road properly. Many cars have a bit of understeer tendency engineered into their suspension, which can help keep it stable if an inexperienced driver makes a quick, sudden change of direction. See oversteer, which is a far more dangerous situation than understeer.
Unibody construction: A method of vehicle construction where the frame, body and major components are welded into a single unit, as opposed to being bolted to a separate frame. It's also called unitary construction or monocoque. Almost all modern cars are unibody construction; it's lighter and allows for the creation of crumple zones, which help protect vehicle occupants in a crash. See also body-on-frame.
Warranty: Coverage provided by the auto manufacturer on its vehicles. All cars have a comprehensive warranty, which covers all items on the vehicle. When this expires, most are also covered by a powertrain warranty, which covers items related to the engine, transmission and driveline. Most will also carry a corrosion warranty, which covers rust perforation. Warranty covers items which fail due to a manufacturer's defect: if your CD player stops playing because the motor burns out, it's covered, but if your child stuck a coin in it, it isn't covered by warranty. Some wear items, such as light bulbs, wiper blades and brake pads usually have a shorter warranty than other items covered by the comprehensive warranty. Most manufacturers also offer extra-charge extended warranty programs.
Wear items: These are parts of the car that work by friction or which undergo wear-and-tear as part of their function, such as wiper blades, brake pads, clutch discs and light bulbs. Wear items usually have a shorter warranty than other items on a new vehicle, because their need for replacement is generally due to wearing out with normal use, rather than to a manufacturer's defect.
Xenon headlamps: Also called High Intensity Discharge or HID headlamps, and pronounced ZEE-non. These headlamps use an electrical discharge within a sealed unit of Xenon gas to produce light. They're more expensive than halogen headlamps, but produce a brighter light (with a blue tinge) and last longer. Some cars use xenon headlamps for low-beams and halogen lights for their high-beams. If both low- and high-beams are xenon, the system is called bi-xenon (it uses a shutter to block some of the light, rather than two bulbs).