Two-Stage Power: A Cost Effective Solution for Equipment's Performance Enhancement



SAE Brasil
Authors Abstract
Recent diesel engines technology development has led to very compact and lightweight power plants.
However those achievements (compactness × output power) faced some technical/economic constraints to be fully implemented in on-highway light vehicles, construction machines and agricultural tractors.
When the installed power is upgraded on an existent equipment the most difficult issue to be solved is the power train.
The very competitive worldwide environment is restricting more and more the added-cost technical solution to improve the vehicles performance/productivity.
Two-Stage Power concept is a means to allow a turbochaged diesel engine to provide two different power curves in order to better explore the vehicle's transmission input torque capabilities with minor production plus cost.
For every kind of equipment the engine is part of a complex system where all components must match in order to assure the desirable level of performance, reliability and durability.
Other areas of the vehicle have to be revised to cope with a higher power level (cooling system, exhaust system, air intake system, etc) but the required investments for those areas are relatively small.
If the gear box/reduction axle input torque limits are exceeded the power train life will be seriously compromised.
The adoption of a huge gear box/reduction axle means a severe cost penalty to the vehicle, since those components are among the most expensive parts of a moving equipment.
The Power train components have input torque limitations, but those limits are not the same for all equipment operating range.
A full authority engine management system could adjust the engine power curve for each specific machine operating point. However full electronic management faces restrictions for applications on low-cost/mid range equipment:
  • Requires long development leadtime and high investments.
  • Needs specialized personnel and equipment for field support (restrictons in certain countries with low sales volumes, huge territories and poor maintenance infrastructure).
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Bolina, A., "Two-Stage Power: A Cost Effective Solution for Equipment's Performance Enhancement," SAE Technical Paper 921482, 1992,
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Nov 1, 1992
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Technical Paper