The Wenatchee Test

The approach mentioned above came from a two-year study we did on the M/V Wenatchee, a 470-ft. passenger ferry which plies an eight mile route between Seattle and Bainbridge Island in Puget Sound. Before the trial, the vessel was equipped with a Flo-Scan advanced fuel metering system. In the next phase, we changed our engine lubricating oil to Chevron 477 20-40 multi-grade. Then we added the technology.


State-of-the-art Interstate Diesel ECOTIP Superstack fuel injectors were installed on the ship's four 4,000 hp, 16-710-G7 diesel engines. GM Electro-Motive, builder of the engines, now makes these injectors available as original equipment on PMI diesel engines, the result of an agreement between the two companies. The injectors incorporate a number of design innovations that effectively lower emissions and improve fuel economy.

To somewhat offset our investment, we slowed down the drive motors slightly, but only on crossings that would not inconvenience our passengers. We reduced the vessel's cruise speed from the usual 180 shaft revolutions per minute (SRPM) to 140 SRPM on non-commute runs. We also slowed landings and departures using specific acceleration and deceleration points.

The impact on the vessel's schedule was minimal. Speed was reduced by between one and three knots, but only one to three minutes were added to the crossing time, a factor that can be easily absorbed on this route during off-peak periods. Normal cruise speed is between 18.5 and 19.1 knots.


The impact of these moves on fuel consumption was dramatic. The ECOTIP Superstack injectors have shown in applications by other users that they can produce fuel savings between three and five percent while eliminating visible smoke and cutting down

other emissions. By combining them with slower running on the Seattle to Bainbridge island route under the conditions mentioned, we can reduce fuel consumption by as much as 33 percent. That could be as high as 150 gallons an hour, or up to 3,000 gallons a day by our calculations. Projecting these figures, we can potentially save up to $1 million per year.