|The front-opening canopy on the Saab Aero X E100 concept|
GM is unveiling the Saab Aero X two-seater sports coupé concept at the Geneva motor show. Taking design cues from Saab’s aviation heritage, the Aero X has no door or windshield pillars; the car adopts a cockpit canopy instead.
The Aero X features a new 400 hp (298 kW), twin-turbo, BioPower V6 engine that is fueled entirely by ethanol (E100), thereby offering net zero tank-to-wheel CO2 emissions.
With carbon fiber bodywork, electronically-controlled suspension and all-wheel drive, the Saab Aero X is projected to accelerate from zero to 100 kph in just 4.9 seconds with a top (limited) speed of 250 kph (155 mph).
Although optimized for E100, the engine management system will make adjustments for any gasoline-ethanol blend.
For optimum handling, the powertrain is mounted entirely behind the front axle line, giving the Aero X a near perfect 50/50 weight distribution. All-wheel-drive, with a variable torque split between the front and rear axles, provides excellent traction and Saab Active Chassis, with continuously variable damping, gives excellent real-life driving safety and control.
The 2.8-liter V6 E100 BioPower engine delivers 400 hp maximum power at 5,000 rpm and torque of 500 Nm between 2,000 and 5,000 rpm.
Pure ethanol (E100) fuel has a higher octane rating of 106 RON compared to gasoline’s 95 RON. Using a 12:1 compression ratio and twin turbochargers running at 1.0 bar boost, the Aero X BioPower engine delivers a hefty 143hp per liter displacement. Turbocharging with E100 fuel allows the use of a higher compression ratio—giving more engine power—than is possible with gasoline because of the risk of harmful knocking (pre-detonation).
The all-aluminum, 24-valve, four-cam engine is a higher-performance version of the current engine in the Saab 9-3 range. For the Aero X, the engine is longitudinally installed and features a Spark Ignited Direct Injection system (SIDI) for optimum combustion; variable inlet and exhaust cam phasing for improved breathing, and dry-sump lubrication for a lower chassis installation and reduced oil pumping losses. Both turbochargers have variable geometry turbine (VGT) wheels to give a quick low-end response.
More durable valves and valve seats are fitted, together with ethanol-compatible materials in the fuel system, including the tank, pump, lines and connectors. The addition of the SIDI system ensures the same cold starting performance as a normal gasoline engine.
The 32-bit engine management system simultaneously controls the ignition timing, fuel injection, turbo boost pressure, air mass measurement and the throttle setting. For minimized exhaust emissions, the two close-coupled catalysts are equipped with electronically controlled, secondary air injection, which gives extremely quick light-off following cold starts.
Turbocharging and bioethanol make excellent partners. In developing this BioPower V6 engine we have been able to take the next step by using E100 fuel, pure 100% bioethanol. That means there are zero fossil CO2 emissions because we are not using any gasoline at all.—Kjell ac Bergström, Executive Director of Saab Automobile Powertrain AB
The 2.8-liter engine is matched to a seven-speed automated manual transmission using a wet double clutch system to allow fast, full throttle, sequential gear changes via the steering wheel paddles. Power is transmitted to all four wheels through a multi-plate clutch, allowing an infinitely variable front/rear torque split.
Suspension is by double wishbones at the front and an independent multi-link layout at the rear. Continuously adjustable damping (Saab Active Chassis) is adopted for enhanced body control, ride comfort and driving safety.
Saab Active Chassis involves processing signals from a number of on-board sensors which measure the vehicle’s vertical, lateral and body-in-roll movements. These inputs are fed into a central control unit, which monitors the behavior of each wheel as often as 100 times per second. It can then calculate and make small adjustments to the valving of each relevant damper as required in just 10-30 milliseconds. Opening the valve increases oil flow to allow softer damping, while closing the valve produces firmer damping. A range of pre-settings can be selected by the driver.