**Elasticity**(automotive technology)

Elasticity of a motor vehicle powertrain describes the condition where the

*rated RPM*of a powerplant is greater than the RPM at which the unit creates its greatest torque; the

*rated RPM*is the RPM at which the

*rated output*(RJ's note: in this case, horsepower) is produced. During an increase in load (in the sense of an increase in

*driving resistance*) such as going uphill or driving into a headwind, this allows you -not- to downshift as your speed falls, due to an increase in torque. The farther the RPM of the maximum torque is (relatively) removed from the RPM of maximum output, the more elastic the motor is.

**Calculating Elasticity**

For motor elasticity, a distinction is drawn among torque elasticity, RPM elasticity, and the total elasticity of a motor.

**Torque elasticity**

eMd = Md2/Md1

Where Md1 is the torque at maximum HP and Md2 is maximum torque

**RPM elasticity**

en = n1/n2

Where n1 is the RPM at maximum output (rated RPM) and n2 is RPM at maximum torque

Total motor elasticity

Total motor elasticity

E = eMd * en = Md2/Md1 * n1/n2

Sometimes

*RPM elasticity*is called "total elasticity" and

*torque elasticity*is called "motor elasticity"; n1 - n2 describes the "elastic range"

**Examples of various RPM elasticities:**

**Puch-Motorcyle**(post-war model), gasoline,

**1.01 (not elastic)**

**Dodge Viper R/T 10**, gasoline,

**1.28**

**Honda motorcycle**(modern sportbike), gasoline,

**1.40**

**Steyr tractor**(modern), diesel,

**1.57**

**Opel Vectra A 2.0i**, gasoline,

**1.93**

**Mercedes 220 CDI**, diesel,

**2.10**

**VW Golf V R32**, gasonline,

**3.10 (very elastic)**

Series-wound electric motors and steam motors, that have their maximum torque available at an RPM of 0, and therefore usually forego transmissions, are considered particularly elastic.