Capri Definitions

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An instrument that indicates the number of revolutions per minute at which the engine is turning. Tappet A pivoting actuator than opens and closes cylinder valves.


A removable-roof body style popularized by Porsche that is similar to a convertible except that it incorporates a fixed, roll-bar-like structure running from side to side behind the front seats.


A housing containing a valve to regulate the airflow through the intake manifold. The throttle-body is usually located between the air cleaner and the intake plenum.

    Throttle-Body Fuel Injection

A form of fuel injection in which the injectors are located at the engine's throttle-body, thereby feeding fuel to more than one cylinder. Such an arrangement saves money by using fewer injectors; but because it routes both fuel and air through the intake manifold, it eliminates some of the tuning possibilities offered by port fuel injection.

    Tire, Tread

Width of a car measured from the center line of the wheels. Sometimes called the track. Also the pattern on the surface of a tire.

    Tires, All-Season

Tires that provide acceptable traction for winter snow and slush driving conditions, without excessively compromising dry and wet traction.

    Tires, Aspect Ratio

Tire aspect ratio is refers to the ratio between the tread(section) width and the sidewall. For example, a 205/50-15 tire would have a sidewall height of 0.50 x 205 or 102.5 mm. Lower aspect ratios(e.g. 40-series) provide superior handling at the cost of increased ride harshness. Tires, M+S rating Tires especially designed to perform well in mud and snow. M+S tires are usually superior to all-season tires under these conditions. The tradeoff is often higher noise and reduced tread life.

    Tires, Ratings

The tire treadwear rating gives an approximate idea of the expected usable life of the tire. A tire rated 300 will probably last 50% longer than one rated 150. Note that each tire manufacturer has its own rating methods. So a Goodyear tire rated at 300 will not necessarily give the same tread life as a Michelin tire rated at 300. It may last longer under the same conditions or it may not. The treadwear number is most relevant when comparing tires by the same manufacturer. The "AB" designation indicates wet traction and temperature resistance, respectively. Wet traction ratings are AA, A, B, and C. "AA" is the best. "C" is the worst. Temperature resistance ratings are A, B, and C. "A" is best. "C" is worst. The temperature resistance rating signifies a tire's heat dissipation capabilities. Excess heat leads to premature tire failure, so cooler running tires last longer.

    Toe Steer

The changes in the direction of a wheel that occur without driver steering input. Toe steer can be caused by ride steer or by deflections in suspension components caused by the stresses of cornering, accelerating, and/or braking on smooth and bumpy roads.

    Toe-Control Link

A lateral link in a multilink suspension designed to control a wheel's direction as the suspension moves up and down.


The intentional nonparallel orientation of opposite wheels. Toe-in is measured by subtracting the distance between the front edges of a pair of tires from the distance between the rear edges of the same pair of tires. The toe-in dimension is positive when the fronts of the tires are turned toward the center of the car.

    Tongue Weight

The actual weight that is pressing down on the hitch attached to the vehicle. This weight should be subtracted to figure payload capacity. Typically, the tongue weight should be 9-11% of the trailer load. Too much tongue weight negatively affects the vehicle's steering, and too little tongue weight means the vehicle may lose traction.


Device for use in, or attachment to, production machinery that is for the assembling of materials or the working of materials by turning, milling, grinding, polishing, drilling, punching, boring, shaping, shearing, pressing or planing.


Set of required standard or special tools needed to produce a particular part; includes jigs, fixtures, gages and cutting tools, but excluding machined tools.


An open sports vehicle generally with an unbroken design line from the hood to the back of the car.


The rotational equivalent of force, measured in pound-feet.

    Torque Converter

A particular kind of fluid coupling with a third element added to the usual input and output turbines. Called ""the stator,"" this additional element redirects the churning fluid against the output turbine, increasing torque. This torque increase, however, is achieved at the expense of rpm and efficiency.

    Torque Steer

A tendency for a car to turn in a particular direction when power is applied. Torque steer is common in front-drive cars because reaction forces created in the half-shafts can generate uneven steering forces in the front tires.

    Torsion Bar

A spring consisting of a long solid or tubular rod with one end fixed to the chassis and the other twisted by a lever connected to the suspension.

    Touring Car

An open car with seats for four or more passengers. Early models had no side weather protection but later were fitted with detachable side screens and curtains. Made until about 1930.

    Traction Control

An electronic control system that prevents wheel spin by detecting when a driven wheel is about to break traction, and then reducing engine power and/or applying the appropriate brakes to prevent it.


A driving technique in which the driver begins to brake before entering a turn and then continues to brake as he eases into the corner. As cornering forces build, the driver gradually feathers off the brakes: trading braking power for cornering grip. By increasing the vertical loading : and thus the traction: at the front tires, trail-braking can improve a car's turn-in.

    Trailing Arm

A suspension element consisting of a longitudinal member that pivots from the body at its forward end and has a wheel hub rigidly attached to its trailing end. A sufficiently rigid trailing arm can provide all of a wheel's location. In that case it is similar to a semi-trailing arm, except that its pivot axis is exactly perpendicular to the car's longitudinal center line

    Trailing Link

A suspension link that is aligned to resist longitudinal motions in a wheel; it is mounted to the chassis ahead of the wheel.


A transmission and a differential combined in one integrated assembly


A gearbox with a number of selectable ratios, used to match the engine's rpm and torque to differing vehicle requirements.

    Tread Squirm

The flexibility in the tire tread between the surface of the tread and the tire carcass. Snow tires, with their small, deep, unsupported tread blocks, have a large amount of tread squirm. Slick racing tires, which have no tread pattern, have very little squirm.

    Trim Level

Vehicle designation assigned by vehicle manufacturers that represent specific equipment packages.

    Tube Frame

A car frame made up of rigid tubing welded together. Tube frames are easier to manufacture in small quantities than unitized frames.


The term that describes the convex curvature on the side of a car body.

    Tuned Intake and Exhaust System

Intake and exhaust systems that, by harnessing the pressure pulses and resonances inside the various passages and chambers of the intake and exhaust manifolds, increase the flow of intake charge into and out of the combustion chambers.

    Turbo Charger

A turbo charger is basically a device that uses exhaust gasses produced by the engine to blow air back into the engine. This causes the engine to produce much more power since it is being supplied with more air and fuel than it possibly could without it. A naturally aspirated engine (non-turbo, standard engine), or "N/A" engine, has to "suck" air through the intake manifolds, throttle body, air filter, etc. With this setup, the most air pressure that can enter the combustion chamber of the engine is a bit less than the current atmospheric pressure. With the turbo, air is being blown into the chamber with positive pressure so that much more air and fuel can enter. A typical turbo charged engine will generate 7 to 10 psi of maximum positive pressure, or "boost".    The turbo charger, or "turbo", is mounted directly to the exhaust manifold, where exhaust gasses pass over a turbine impeller that is attached to a short shaft. On the other side of this shaft is a compressor turbine, which pulls outside air in through the air filter and blows it into the intake manifold. So basically, the energy from the expelled exhaust gasses, which would normally be wasted on a N/A engine, is being used to pump air back into the engine.

    Turbo Lag

Within a turbocharger's operating range, lag is the delay between the instant a car's accelerator is depressed and the time the turbocharged engine develops a large fraction of the power available at that point in the engine's power curve.


The moment of transition between driving straight ahead and cornering.

    Two-Stroke Cycle

An internal-combustion engine that requires only one revolution per cylinder or two piston strokes (up and down) to achieve a power stroke. Rarely used in automobiles.

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