Fuel Efficiency SUV Notches 10 Mpg Improvement Vs. Baseline Vehicle

March 1, 2015

Kami Buchholz

Schaeffler's fuel efficiency demonstrator nets 35 mpg combined mileage rating via in-house simulations and measurements.

A demonstrator SUV has achieved a 35 mpg combined city/highway rating following a phase-two technology retrofit. Schaeffler’s fuel efficiency demonstrator is based on a 2013 Ford Escape with a 24-mpg combined mileage rating when production-attired in AWD, a 2.0-L EcoBoost engine, and a six-speed automatic transaxle.

“The economical solutions achieve a 44% improvement in fuel economy compared to the baseline vehicle and meet 2025 CAFE standards,” Bruce Warmbold, CEO Americas for Schaeffler Group USA Inc., said during media days at the 2015 NAIAS.

That 35 mpg combined mileage rating is based on Schaeffler simulations as well as chassis and dynamometer measurements. Independent, third-party testing will be scheduled in the coming weeks.

In the project’s first phase, the Escape was mechanically optimized with friction-reducing alterations to the valvetrain and balance shaft. The demonstrator also was fitted with a thermal management system as well as Schaeffler’s AWD disconnect clutch, permanently engaged starter, and latching valve. The vehicle rides on low-rolling resistance tires from Continental. (See Schaeffler Tech Demonstrator Achieves 15% CO2 Reduction.)

The various phase-one technology changes enabled the demonstrator to meet 2020 CAFE standards, which are estimated to cost less than $40 per percent of fuel economy improvement, according to Jeff Hemphill, Schaeffler North America’s CTO.

To meet 2025 CAFE regulations, the Efficient Future Mobility North America-dubbed demonstrator underwent more extensive modifications. The vehicle kept its phase-one torque converter-equipped automatic transmission and 2.0-L combustion engine, and added a 48-volt parallel hybrid system in phase two’s electrification retrofit.

Front-end accessory drive components are in a conventional layout with the power-flow routed from the transmission to the belt drive using a Schaeffler designed pendulum tensioner.

In an Automotive Engineering interview at an October 2014 Schaeffler technology symposium in Detroit, Philip George, Director of Advanced Development for Schaeffler Group North America, talked about the vehicle’s power-flow from the transmission to the belt drive.

“Because torque is either put into the motor-generator unit or it’s taken out of the motor-generator unit, the slack side of the belt changes depending on the vehicle’s operating mode,” George explained. “This unique belt-tensioner is a less complex way to manage the front-end accessory drive vs. a typical production application that uses multiple tensioners.”

Schaeffler’s clutching system enables coupling or decoupling of the accessory chain from the transmission’s power flow. In a disconnected mode that allows the water pump, air conditioning compressor, and other accessories to be powered electrically. The engine can operate independent of the accessory chain since the system taps into the transmission’s input shaft.

Electric power can drive the transmission pump, so a separate pump is not needed to keep the transmission alive like it would be with a normal hybrid system, according to George. A single pump is used for engine-powered operation and electrical operation of the front-end accessory drive.

The motor-generator unit recovers kinetic energy directly from the vehicle independent of engine operation. Excess energy is stored in a 48-volt, 1 kW·h lithium-ion battery and used as needed for either boosting or load-point shifting to improve overall powertrain efficiency. (See "Schaeffler Electrifies Its Fuel-Efficiency Demonstrator, Aims for 35 Mpg Combined Rating")

According to Hemphill, “We still need to finalize a calibration that is acceptable to North American consumers and make our final confirmation measurement.”