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The auto industry is responding to the environmental and energy conservation concerns by gradually producing mass-production of hybrid electric vehicles (HEV) as well as conducting development of fuel cell vehicles. One of many challenges of putting a customer-satisfactory HEV on the road is to develop “imperceptible” engine start-stops. This paper presents an investigation of engine start-stop NVH in a power split powertrain HEV. This investigation includes analyzing the root cause of engine start-stop NVH issues, developing the methodology and metric to gauge NVH improvement, and developing measures to resolve the NVH issues. The effectiveness of some proposed counter measures are presented and discussed through vehicle testing results. Finally, the overall NVH improvement of engine start-stop with implementation of practical counter measures is also presented.

The 2013 Ford Fusion will be launched with an optional automatic engine start-stop feature. To realize engine start-stop on a vehicle equipped with a conventional powertrain, there are two major challenges in the vehicle system controls. First, the propulsive torque delivery from a stopped engine has to be fast. The vehicle launch delay has to be minimized such that the corporate vehicle attributes can be met. Second, the fuel economy improvement offered by this technology has to justify the cost associated with it. In pursuing fuel economy, the driver's comfort and convenience should be minimally impacted. To tackle these challenges, a vehicle system control strategy has been developed to accurately interpret the driver's intent, monitor the vehicle subsystem's power demands, schedule engine automatic stop and re-start, and coordinate the fast and smooth torque delivery to the wheels.