Allison stated earlier this week that with the increasing appeal of natural gas, fleet operators are specifying Allison Automatics for their natural gas powered vehicles.
According to the company, Allison Automatics are perfectly suited for natural gas powered vehicles, both compressed (CNG) and liquefied (LNG), in a wide range of applications because of the inherent benefits of Allison’s patented torque converter technology and full-power shifts.
A natural gas engine behaves differently than a diesel engine. Engine speeds can’t be controlled as quickly and easily as they can on a diesel. When a driver lifts off the throttle, the engine speed takes a finite time to respond, and this response time is longer with a natural gas engine.
Allison says its automatics transmissions’ full-power shifts provide smooth, seamless shifts, which do not require the driver to go to zero throttle, so slower response time-to-throttle cycles are not an issue. Manuals and automated manuals require the engine to be at zero throttle to shift.
Natural gas engines generally have lower horsepower and torque compared to diesel engines. To counter this drawback, Allison says the torque multiplication created by its torque converter compensates for this by putting more power to the wheels, which results in greatly improved startability.
Finally, some natural gas engines do not offer an engine brake and others have considerably less engine braking torque available compared to diesel engines. Allison solves this with the simple addition of an Allison retarder.