Twins for Saab's Aero turbodiesel

Although a relatively late starter in the field of turbodiesel power, Saab has leapfrogged many of the local oil burners with an impressively powerful new twin-turbo powerplant.
Indeed, the punch of the new turbodiesel is sufficient to earn it a place in the Swedish brand's Aero 9-3 lineup, where it is available in Sport Sedan and SportCombi versions, in both six-speed manual and six-speed auto form.

The Aero label has traditionally been reserved for Saab's highest performing models.

The new engine is a development of the current four-cylinder 16-valve 1.9TiD engine, suitably toughened up and reconfigured to lift power from 110kW to 132kW, and torque from 320Nm to 400Nm. Auto versions of the new TTiD Aero retain the same power output, but torque drops to 370Nm to place less stress on the transmission.

Saab claims the manual transmission Sport Sedan sips diesel at an average rate of 5.7L/100km, while the manual SportCombi drinks at the rate of 5.8L/100km. The auto sedan rises to 6.8L/100km and the auto SportCombi to 6.9L/100km.

As well as employing two-stage turbocharging, the new engine gets reinforcements for the cast-iron block, alloy cylinder-head and all internal components to handle the extra power.

The TTiD engine features sequentially turbocharging. A smaller turbo looks after low rpm while a bigger one joins in above 1500rpm to help high-speed power. Above 3000rpm only the larger turbo is activated.

Compared with the single-turbo diesel, the TTiD engine adopts a higher boost pressure (1.8 bar against 1.4 bar) offset by a reduced compression ratio of 16.5: 1 (17.5:1 for the single-turbo).

Visible emissions are controlled by a low-maintenance particulate filter.

The TTiD engine's torque promises decent accelerative punch, yet drops prices $8000 below those of equivalent turbo V6 petrol Aero models. No TTiD Aero convertible is as yet on offer.

Saab claims its new twin turbo TTiD diesel is a "world first" in the premium car segment.

BMW has employed sequential turbocharging on its high-performance diesel powerplants for some time. The 535d introduced the Bavarians' system in late 2004.

Currently available in the X5 3.0sd only Down Under, the latest bi-turbo Beemer oiler is also offered in 3, 5 and 6 Series models in Europe. The maker also has a new twin-turbo 123d diesel 1 Series in selected markets. 

Saab Aero TTiD pricing:
Aero TTiD Sport Sedan manual - $62,600
Aero TTiD Sport Sedan auto - $65,100  
Aero TTiD SportCombi manual - $65,100 
Aero TTiD SportCombi auto - $67,600 

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