Saab previews 9-4X with BioPower

  • 31-Mar-2008 07:42 EDT
Saab 94.jpg
Saab 9-4X BioPower

The 9-4X BioPower makes public Saab’s intentions to enter the growing crossover segment. It combines an engine optimized for ethanol with vehicle design elements developed by a team under Anthony Lo, General Motors Europe’s Director of Advanced Design.

The concept’s E85-fueled 2.0-L I4 turbo engine delivers 300 hp (221 kW) at 5400 rpm and 400 N·m (295 lb·ft), for a high specific power output of 150 hp (112 kW) per liter. This compares with 245 hp (183 kW) and 353 N·m (260 lb·ft) in the gasoline-optimized version.

The cylinder head was altered for direct injection, said Kjell ac Bergström, President and CEO, Saab Automobile Powertrain. Current ethanol-capable production engines are optimized for gasoline but driveable on ethanol, he said. “What we’d like to do is optimize them [for] ethanol and make them driveable on gasoline.”

Tuning for the higher octane of ethanol allowed the engine’s compression ratio to be raised to 10.5:1 (vs. 9.2:1). The engine can still be run on gasoline, the management system adjusting ignition timing and turbo boost to ensure there is no pre-detonation.

In addition to direct injection, engine efficiency is improved by continuously variable valve timing on inlet and exhaust sides, which enhances turbo response at low engine speeds and contributes to a wide spread of torque. On E85 fuel, 400 N·m (295 lb·ft) is generated from 2600 to 5100 rpm, with 85% available from just 2000 rpm. Boost pressure at maximum torque is 1.2 bar (17.4 psi).

The engine is paired with Saab’s new XWD all-wheel drive, its active management splitting torque delivery between the axles and between the rear wheels via an electronically controlled limited-slip differential. Up to 40% of the torque can be transferred between the rear driveshafts to the wheel side with more grip. This improves cornering stability by making the rear of the car more closely follow the direction of the front wheels.

The concept looked to be nearly production-ready. Its architecture “is a mix between the Theta and Epsilon architecture that will be used for the future Saab 9-5 and 9-3 and the Opel Insignia,” said Bergström. The TE (Theta Epsilon) architecture is Epsilon from the firewall forward (primarily for larger engine packaging) and Theta from the firewall rearward. “If someone wants to put in a big V8 engine with a charger or whatever, that might not package in the Epsilon but it will package in the TE,” he said.

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