Telma

Performance can be 110-300% of rated engine horsepower

Power depends on Telma size chosen

Activation/Deactivation time 120 milliseconds

Completely compatible with ABS because activation is progressive and deactivation time complies with the time required by ABS manufacturers so that a retarder does not interfere with ABS braking control

No on/off switch is needed. ABS automatically disables Telma before a wheel slip condition occurs. The driver does not need to make the choice of when to turn off the retarder alleviating liability in case of accident.

Re-activation of Telma after an ABS event is progressive with a one second interval between stage re-activation if the driver still has his foot on the brake pedal after the ABS event is over.

Energy is dissipated directly to the air. Performance is not limited by the engine cooling system

Silent when operating.

Weight is higher than other retarders

Electrical power consumption is higher than other retarders

 

Engine Brakes

Performance is 60-110% of rated engine horsepower

Performance depends on Displacement and gear chosen

Activation/Deactivation time 100 to 200 milliseconds

Turn off under slippery conditions because activation is not progressive. The driver must decide when to turn off increasing liability in case there is an accident.

Energy dissipated through exhaust and cooling system

Loud popping noise when operating

Braking torque transmitted through transmission.

Complete and sudden loss of braking torque if transmission goes out of gear

 

 

Exhaust Brakes

Performance is 50 to 75% of rated engine horsepower

Performance depends on displacement and gear chosen

Activation/Deactivation time 100 to 200 milliseconds

Turn off under slippery conditions because activation is not progressive. The driver must decide when to turn off increasing liability in case there is an accident.

Energy dissipated through exhaust and cooling system

Loud popping noise when operating

Braking torque transmitted through transmission.

Complete and sudden loss of braking torque if transmission goes out of gear

 

 

 

Hydrodynamic retarder

Performance can be 110-200% of rated engine horsepower

Power depends on cooling system capacity

Activation/Deactivation time is 1.6 to 2.3 seconds. Loss of fuel economy if acceleration occurs quickly after braking such as stop and go applications

Turn off under slippery conditions because de-activation is too slow to be compatible with ABS. The driver must decide when to turn off increasing liability in case there is an accident.

Energy dissipated through cooling system

Almost Silent

Weight is higher than engine or exhaust brake but lower than electromagnetic retarders

Limited braking at low and high rpm