Transmissions (Continued…)

• Volvo’s transmission management technology calculates the optimum moments to shift and allows the vehicle to continue accelerating or decelerating based on the driver’s input and external demands at that moment in time. “The technology eliminates the ‘miss-shifts’ that occur with manual gearboxes during demanding moments in a duty cycle,” Moore stated. “These shifting points vary from truck to truck depending on the application, driving styles, and chassis options. These calculations allow the vehicle to operate in the most efficient manner at that point in time. Another benefit of this approach that is often overlooked is an improved driver experience.” … “Our internal testing has shown a potential improvement for the customer of up to 3%. A very good driver can probably match the Volvo I-Shift, but it would be hard for a good driver to do this every day,” Moore said. “Electronic control units don’t get headaches, illnesses, injured shifting arms, lack of sleep, etc. – situations that prevent good drivers from optimizing every driving shift every day of the year.”
• In terms of spec’ing your transmission, the degree of downspeeding will be determined by your type of transmission. “You may spec an automated manual for lower engine cruise RPMs than a manual since the transmission is doing the shifting work and typically there will be more shifting the lower the cruise RPMs,” said Jim Bingaman, Peterbilt application engineering manager. “These transmissions will shift at the optimal times and take less driver skill to operate.”

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• On the transmission OE side, Ryan Trzybinski, Eaton product strategy manager, Linehaul, went on to explain the importance of working with engine makers to understand where the optimal or “sweet spot” of the engine is to help drive Eaton’s shift decisions so the transmission can downshift at the right time to keep the engine operating in the most efficient zone. “The ‘small step’ technology is designed to do just this,” Trzybinski said. “The step size between 9th and 10th gear determines how much the RPM will increase when a downshift is made. A traditional overdrive transmission [Eaton ‘C-Ratio’] has an overdrive ratio of 0.73 which is a 34 percent step from 9th gear. For a given road speed and axle ratio we’re discussing here, that will increase the engine around 350 RPM. The Eaton ‘small step’ technology has a step size of 26% so the RPM will have a more modest RPM increase of around 250 RPM. That helps keep the engine in the sweet spot and also at lower RPMs more often, thus saving fuel.”
• Features like this fall under the transmission management umbrella where fuel efficiency is pulled out of optimizing the shifts in automated-manual or automatic transmission. The effect of transmission management technology on fuel efficiency is difficult to pinpoint because fuel efficiency depends so much on duty cycle and many external factors that vary from customer to customer.