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What does torque mean? Gearhead terms explained

Torque, RPM, AWD, understeer / oversteer, limited slip differential and other automotive terms defined.
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Defining torque and other common automotive terms

Torque, stance and RPM are just a few terms that you might find confusing if you’re not an auto aficionado. So what do these terms mean anyways?

Learning some of the lingo might help you out next time you visit your mechanic or when talking cars with your buds, you might actually understand what’s going on instead of just smiling and nodding. Here are some common automotive terms broken down:

Torque

Torque is a measure of rotational power. A vehicle with more torque, will provide more power to the wheels as they rotate. Torque is most important to performance vehicles and trucks that are used for heavy hauling or towing.

RELATED: Don’t Confuse Torque with Power

Stance

This refers to how a vehicle sits on its wheels, tires & suspension which can affect alignment & drivability. You might hear this term when discussing a vehicle that has been lowered. When lowering a vehicle stance becomes particularly important because it will affect the geometry of the suspension and make driving difficult, if not impossible if done incorrectly. Stance also refers to the rake (lower front end than rear end) and the camber of the tires (inward tilt of the top of the tires). Extreme camber angles will greatly reduce the lifetime of the tires because it wears the inside of the tire faster than the outside.

Direct Injection

The gasoline is highly pressurized and injected via a fuel rail directly into the combustion chamber of each cylinder as opposed to the intake manifold  or cylinder port. By injecting the fuel at a high pressure, the size of the gas droplets (atomization) is reduced thus allowing the engine to become more efficient and generate more power.

RELATED: Direct injection boosts efficiency

Boost

In automotive applications, Boost refers to the amount that the intake manifold pressure increases above atmospheric pressure. Boost from a Turbocharger or Supercharger compresses the intake air charge before it enters the combustion chamber of the engine. The boost pressure can range, but common pressures for OEM engines range from 5 pounds per square inch (PSI) to 10 PSI. Compressing the air charge requires slightly more fuel to balance the air-fuel ratio (14.7:1) and allow the vehicle to run properly. “Boosting” an engine increases the power and torque output levels and the efficiency of the engine as well.

RELATED: Turbos top superchargers as fuel saver

LSD (Limited Slip Differential)

Power is delivered to the differential and is sent to each of the drive axels allowing for some difference in output speed between the drive wheels. A non-limited slip differential delivers power to the differential and directs that power to the wheel with the most traction. Sometimes referred to as “one-wheel-peel”.

Oversteer / Understeer  

Oversteer is when traction or grip is lost in the rear end of the car, causing the rear to swing out (if turning left, the rear end will swing out to the right). This is more common in rear wheel drive vehicles with higher horsepower.

Understeer is when traction or grip is lost in the front end of the car, causing the front of the car to continue forwards even if the steering is turned. This is more common in front wheel drive vehicles.

Torque Steer may also occur in front wheel drive vehicles. This happens when the power being sent to the front wheels overcomes the traction of the tires and causes the car to slide left or right.

Related: How to survive a drive over an icy bridge

RPM

Revolutions Per Minute is a unit of measure for the frequency of rotation around a fixed axis in one minute. In automotive terms, how many times a minute the crankshaft journals rotate around the centreline of the crankshaft. On your dashboard, this rotation is indicated as engine speed (RPM) and is an indication as to how hard the engine is working. Remember, the higher the RPM, the more fuel you burn!

4WD vs. AWD

4WD:

Delivers power to all 4 wheels evenly and constantly, without a difference in rotational speed from side to side. The power is sent to each wheel via a transfer case which usually has various speeds: 2-hi, 2-low, 4-hi & 4-low.

AWD:

Delivers power to all 4 wheels evenly but can be vectored front to rear or side to side depending on the system the vehicle is equipped with. Most systems only drive the front or rear axels until the need for AWD is necessary, then allocates the power to the wheels that have the most traction.

How to Read a Tire

Understanding what those letters and numbers mean on your tire is crucial to safety and performance.  Let us break it down for you:

P references the type of vehicle the tire should be fitted to, in this case Passenger.

185 is the width of the tire in mm and 75 refers to the aspect ratio, aka “profile”. This is the height of the tire from the bead to the tread in relation to the width(185).

In other words 75 refers to 75% of 185 or a tire height of 138.75 mm.

R stands for radial, most cars on the road today are outfitted with Radial tires.

14 is the diameter of the wheel that the tire is designed to fit.

82 indicates a load index, basically the max weight that a tire can carry under safe maximum inflation. The number is an assigned value corresponding to a load index chart.

Finally S is the speed rating, designating the max speed at which a tire is certified to travel under safe operating conditions.

What automotive terms are confusing for you? Let us know in the comments below.

Related: How to tell whether your tires are salvageable

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