To help bolster its share of the diesel market in Europe, Saab has rolled out two new versions of its 9-3 sedan using its latest generation of diesel technology, the 1.9 TiD. The new engines replace the older 2.2 TiD, and deliver better power, improved fuel efficiency and better emissions control than their predecessors.
Jointly developed by GM-Fiat Powertrain, produced in Italy and already in use in various Fiats, Alfa Romeos and Vauxhalls, the new 1.9 TiDs are a good example of the rapid improvements in diesel technology.
Common rail technology provides consistently high injection nozzle pressures of 1,600 bar, independent of the prevailing engine speed or load. This platform allows the use of small, multiple injections of fuel, between two and five, to release as much energy as possible from a given amount of fuel.
This extremely efficient combustion process pays dividends in a number of key areas. Apart from improving fuel consumption, emissions and power, it is crucial in helping to iron out the strong vibrations traditionally associated with compression ignition. The Bosch ECM [Engine Control Module] continually adjusts the number, frequency and size of the injections according to three main parameters: current engine speed, requested throttle setting and engine coolant temperature. Each injection pulse may be separated by as little as 150 microseconds, delivering a quantity of fuel as tiny as one cubic millimeter.
The turbocharged diesel is thus characterized as common rail, direct and multiple injection. Performance, fuel efficiency and emissions stats are impressive. The cars average 40 mpg (US gallons) combined, and meet Euro4 emissions criteria.
On the emissions side, the cars use Exhaust Gas Recirculation (EGR) for quick warm-up and reduced emissions, combined with a new particulate filter system that is enabled by the engines combustion management.
The 1.9TiD powertrain includes the most advanced diesel particulate filter on the market, enabling Euro 4 emissions compliance. Unlike other particulate traps, it is maintenance-free and self-cleaning, requiring no additives or periodic replacement.
Located in the exhaust system downstream of the close-coupled catalyst, the housing for the filter also includes a secondary oxidation catalyst to remove residual hydrocarbons (HC). The exhaust gases pass through this first, before entering the filters ceramic core, made from a honeycomb of silicon carbide.
This is perforated along its length by a matrix of microscopic channels, which collect the particulates as deposits from the exhaust. In order to clean the filter and to keep the exhaust flow as free as possible, these deposits are periodically burnt off by short pulses of over-fueling. These briefly raise exhaust temperatures to the required level of 600º C. The process is automatically initiated when back pressure in the exhaust system reaches a certain level and is completely undetectable by the driver.
This innovative solution has been made possible through the fueling flexibility provided by the engines multiple injection strategy. The self-cleaning process takes place whenever necessary, irrespective of throttle load or engine temperature.
Excellent stuff, and its clear why there is increasing appetite for diesels overseas. (Now, to see if Saab can increase its share of the diesel market with offerings like these.) These new generations of diesels seem well suited for the type of driving in the US—and with fuel efficiency numbers such as those above, upping the number of diesels in the mix here would reduce our overall fuel consumption as we work toward new engine and fuel platforms.
I think we have two problems. The first problem is the public perception of diesels (slow, stinky, etc.). The second problem is that the automakers dont try to change the first problem through leveraging their product innovation and good, sound marketing. Instead, we seem to keep plodding down mostly the same advertising, marketing and sales paths, with a few notable exceptions, such as Toyota.
I think Toyota will continue its rise in the US because of the way it talks to its customers through its products and its marketing. The fact is that Prius sales really represent a sliver of overall Toyota business—but Toyota is seen as innovative, serious about larger issues, and not afraid to raise those issues with consumers. No wonder its results are the best ever.
GM (which owns Saab), on the other hand, has spent time and money advertising the hydrogen way of the future, but has not put much advertising effort in the US on immediate products with immediate benefits in fuel efficiency and so on. (At least, not that I have seen aside from a small push on E85 that started last year and continues this year.) Yet it is the largest producer of Flexible Fuel Vehicles (FFV) (burning gasoline or E85—85% ethanol, 15% gasoline). Look at it another way. GM sells more FFV vehicles than Toyota does Priuses. But which carmaker does the average US consumer regard as the greener? (Leave aside the infrastructure problem of numbers of E85 fueling stations for this.)