9-3 Viggen Drivetrain


With 252 Ib.-ft. of torque on tap, the 9-3 Viggen has all the right moves

Norcross, GA - Saab's new high output turbocharged 2.3L 9-3 Viggen Coupe is even more fun than a flight simulator, thanks to its impressive turbo and torque combination. Starting with the engine block from the 9-5 series, replacing key internal components and integrating a larger turbocharger, Saab's engine development team has endowed the Viggen with the ultimate expression of Saab turbo power.

As with all Saabs, company engineers prioritized the engine's torque output rather than horsepower. Saab's engine philosophy focuses on the force that gets mass moving, a solution that delivers excellent acceleration and passing performance from an efficient, small displacement powerplant. With 225hp at 5,500 rpm, and impressive torque of 252 Ib.-ft. available from 2,500 rpm all the way through 4,000 rpm, maximum torque is on tap for 30% of the useable power band. This leading mid-range performance makes the new 9-3 Viggen one of the world's most entertaining front wheel drive automobiles. More importantly, it provides the pilot of a Viggen power on demand for safe, fast and decisive overtaking to avoid potentially dangerous situations.

To put the Viggen's power into perspective, consider the following: The 9-3 Viggen's engine is 12% more efficient at producing horsepower per liter of engine displacement than a 1999 Porsche 911 Carrera. More importantly, the Viggen is a full 44% more efficient at producing Ib.-ft. of torque per liter of engine displacement. To enable the front tires to cope with the amount of torque available, maximum torque is electronically limited in first gear to 184 Ib.-ft. and in second gear to 243 Ib.-ft.

The incredible power output of the Viggen's engine is primarily attributable to the larger turbocharger, which produces maximum boost pressure of 1.4 bar, or a full 20 psi, and assisted by less restrictive air intake pipes and a new exhaust system. Saab's engineers have ensured engine integrity under high boost levels. All Saab turbochargers, the Viggen's included, have been oil and water-cooled since 1988. Reinforced alloy pistons with strengthened gudgeon pins are utilized. To alleviate any heat concerns for the pistons in such a highly boosted engine, oil cooling jets at the base of the block, near the crankshaft, spray oil at the underside of each piston for cooling. To ensure that the valves live with the heat, intake valves are sodium filled and exhaust valves are made out of a special high-tech alloy called Nimonic. Nimonic is an alloy with very high nickel content making it extremely resistant to heat. This material is commonly found in aircraft components that are subjected to high pressure and temperature, such as the exhaust nozzles in jet engines.

The Viggen's highly modified and responsive engine is the first 9-3 to be controlled by Saab's own Trionic T7 engine management system from the 9-5 series. The brain of Trionic T7 is a 32-bit microprocessor, capable of making two million calculations per second. Trionic is so powerful, it simultaneously controls fuel injection, ignition timing and turbo boost pressure on all 9-3s, as well as the fly-by-wire electronic throttle on the Viggen and all 9-5s.

With the inclusion of electronic throttle control from T7, as the driver depresses the accelerator pedal, it turns the pedal position sensor located in the throttle body. The computer reads this as a request for torque and then directs the throttle motor to turn the throttle plate until its position sensor value corresponds with the requested value. Turbo boost pressure is also increased, if necessary, as greater amounts of torque are requested. The primary advantage of electronic throttle control is that it overcomes the added inertia that's present when using a larger turbocharger. It does so by demanding more torque from the engine than the driver has actually requested.

Kenth Johansson, one of Saab's product development engineers, explains: "When accelerating, a driver is actually asking for more air speed, and consequently more torque. However, the larger turbo is still governed by the laws of physics, so there is a delay. We have minimized that delay by controlling the software more precisely and by keeping losses in the turbo wastegate as low as possible. We program the Trionic T7 computer to manipulate the throttle position - opening it further than the driver has requested - so the engine can reach the driver's requested torque level more quickly. It's an electronic slight of hand, but the end result is what matters: torque on demand for the driver."

Another advantage of Saab's new Trionic T7 engine management system is the consistency of turbo efficiency, whether at low or high altitudes. The Viggen's high output turbo delivers the same maximum 252 Ib.-ft. of torque from sea level all the way up to 9,750 feet. A charge air pressure sensor sends information to the Trionic computer indicating the pressure level in front of the throttle. Denser air requires a smaller throttle angle, so this is adjusted automatically to the ambient conditions, achieving maximum torque as quickly as possible.

The tremendous power and torque available from the Viggen engine is transferred to the pavement via an upgraded clutch assembly, larger diameter- stronger driveshafts and strengthened CV joints. The earth-bound Saab 9-3 Viggen, like its jet fighter namesake, is designed to deliver the unmistakable thrust of Saab turbo performance while retaining traditional Saab character traits.

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