I just recently did a search for the TTiD engine to confirm some information in an article I’m writing for The Truth About Cars. To my dismay, I didn’t have a specific article just on this engine.
So here, separate and discrete, is the juice on the TTiD, twin-turbo diesel engine as seen for the first time in the 2008 Saab 9-3.
The 9-3 range features a powerful new four cylinder diesel engine with a unique two-stage turbocharging system, a world ‘first’ in the premium car segment, giving class-leading levels of efficiency. The 1.9-liter, 16-valve engine, badged TTiD,produces 180 hp (132 kW) and 400 Nm of maximum torque, specific power outputs that are unmatched among competitor products on the market. With combined fuel consumption of 5.9 l/100k projected for the Sport Sedan, this engine also offers class-leading economy, together with in-gear performance on a par with the 2.8V6turbo gasoline engine.
The two-stage turbocharger housing is integrated with the exhaust manifold and contains two turbochargers of different sizes. The pair of turbine/compressor wheels are sequentially mounted and each is able to by-pass the input and output feeds of the other, while also being able to operate in tandem.
This arrangement provides a driver with ‘the best of both worlds’: good, instant torque at low engine speeds – via the low-inertia small turbo when the exhaust pressure is light – and strong ‘top end’ power at higher revolutions, when the bigger turbo is engaged.
Saab’s two-stage turbocharging uses a system of by-pass valves that directs the exhaust gas stream between the two turbine wheels and also separates the air intake charge from the compressors. From tick-over to 1,500 rpm the exhaust feeds only the small turbo. Between 1,500 and 3,000 rpm the flow is split between both turbines, giving stronger boost and ensuring a smooth transition phase to full power operation, above 3,000 rpm, when only the larger turbo is engaged.
The compact design provides more efficient packaging than systems using two separate turbochargers linked together externally in series. It ensures that the complex control and regulation of gas flows on both the exhaust turbine and intake compressor sides is achieved with a minimal number of seals and connections.
The TTiD engine is a substantial development of the current 16-valve 1.9TiD unit, using common rail, direct and multiple fuel injection. It operates with a maximum boost pressure of 1.8 bar(1.4 bar for the current engine) together with a slightly lower compression ratio of 16.5: 1 (17.5:1). The cast-iron block, alloy cylinder head and all internal components are strengthened as necessary to withstand the higherthermal pressures.
The exhaust gas re-circulation (EGR) system is characterized by extremely efficient cooling and now includes an electronically controlled by-pass for improved emissions. This feature, together with the fitment of a maintenance-free exhaust particulate filter, is expected to ensure compliance with more stringent future Euro 5 emissions standards.
Other technical enhancements include the adoption of a larger air-to-air intercooler, for better cooling of the intake charge; the introduction of more efficientpre-heating elements inside the cylinder head, for faster starting in cold conditions; and the use of a weight saving plastic intake manifold.
The Saab TTiD engine meets a growing demand from drivers unwilling to sacrifice performance in the interests of fuel economy. With power characteristics typical of a much larger engine, it is an example of Saab’s commitment to ‘right-sizing’, the achievement of ‘big’ engine performance without the usual drawbacks, such as extra weight, bulk and higher fuel consumption.
In recognition of its outstanding performance, the Saab TTiD engine is available in Aero specification, as well as Linear and Vector. It is offered in all three body styles, in addition to the current 120 (88 kW) and 150 hp (110 kW) 1.9 TiD engines, with a choice of six-speed manual or automatic transmissions.