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The purpose of this study was to evaluate automatic transmissions in a forestry context by comparing their performance with that of standard manual transmissions, and assessing the possibility of improving fuel efficiency by adapting the engine and automatic transmission performances to the vehicle's load. Long-haul test results showed that during the test day, the degradation in driver performance with the manual transmission truck translated into a 2.9% relative increase in fuel consumption when compared with the automatic transmission truck. The fleet data assessment indicated no obvious difference in fuel consumption between the performance of automatic transmissions and manual transmissions. One system for adapting engine performance to vehicle load uses an onboard weigh scale to determine the load status of the vehicle.

The main objective of this project was to compare the fuel consumption and dynamic performances of direct-drive and overdrive transmission tractors. Fuel consumption was evaluated at constant high speed and on various road profiles, while the dynamic performance was assessed on various road profiles only. The SAE Fuel Consumption Test Procedure (J1526) was used for constant high speed fuel consumption track test evaluations. The direct-drive transmission tractor consumed less than the overdrive transmission tractor, even though it was heavier. The testing on various road profiles was conducted using a towing dynamometer, for comparing the dynamic capability of the tractors when simulating the same towing load on two hilly road profiles: the Townes Pass path (in the Rocky Mountains) and the Saguenay path (in the Saguenay region of Quebec). Each tractor was to haul the set load along the given path while trying to attain 90 km/h speed.

This study aimed to evaluate the impact of the duration of idling on engine warm-up and engine cool-down, and to assess the effectiveness of an energy recovery system. The results confirmed that there is no need to idle an engine for extended periods after a cold start to warm it up. It is more efficient to idle the engine for a short period, and then drive the vehicle or operate the machinery at moderate loads until the engine warms up to normal operating temperatures. The tests also confirmed that the engine retains enough heat for easy starting even after being shut down for a few hours and there is no need to idle an engine for fear of having cold start problems. The tests with an energy recovery system, which circulates engine coolant to the heater after the engine is shut down, showed that the system can maintain cab temperatures at comfortable levels even after the engine has been shut down for a few hours.