The buzz-word globally when it comes to internal combustion engines is ?downsizing? — which in fact does not mean downsizing an engine in the strictest literal sense but instead achieving such aims with a large gain in dynamic output terms. In short, it comes down to reducing engine size and bulk while achieving the same dynamic outputs of a larger engine — this in tandem with frugal small-engine fuel consumption and unwanted exhaust emissions.

To this end, General Motors — the automotive giant that once produced gargantuan cars with similarly gargantuan engine and fuel consumption habits — unveiled its all-new high performance 2.9-liter V6 turbo-diesel engine with state-of-the-art fuel injection, force-fed breathing, the latest in combustion technology, frugal fuel consumption habits and low emissions. No longer in love with those monster low-tech, gasoline-guzzling-overhead-valve ?muscle car? engines, GM is now fully involved in the ?Green? side of automotive technology.

But more surprisingly, the all-new engine will be sold mainly in Europe in the 2009 in the new Cadillac CTS. The latter course was chosen as prices of fuel are becoming more prohibitive in Europe and should at least give the principle of diesel engine use a good head start before selling in the USA. What is even more interesting is the fact that GM has hailed the engine to be part of what it calls, ?Cadillac's performance-oriented brand character?. Surprising, but it does point to a major shift.

The all-new Eurocentric engine is now bequeathed with a compact dual overhead cam 24-valve V6 set-up. What?s more, it?s a diesel. A Cadillac with a diesel, you may scoff? Precisely, and more so the reason why it?s being aimed at Europe instead of the USA for the time being. And that?s not all — the engine belongs to a new GM family of diesel engines featuring its innovative closed-loop combustion control system design that will meet future emission standards too. Another upside is the motor can be installed longitudinally or transversely and can be adapted to a wide range of two- or four-wheel-drive vehicles.

It must then also be of no surprise that the new engine is joint venture of GM Powertrain's European operations in Turin, Italy, with VM Motori a company that has been at the forefront of internal combustion engine technology since 1947. GM Powertrain will focus mainly on the development of clean combustion processes, electronic engine control and exhaust-gas after-treatment, as well as the calibration and integration into GM vehicles.

GM?s ?closed loop system? is better explained as a, ?closed-loop fluidic control servo system for a vehicle having an internal combustion engine provided with a variable Venturi carburetor having an axially-shiftable spool that is operated by a vacuum motor?. More simply, the system acts automatically through the motor to maintain the ratio of fuel-to-air supplied by the Venturi carburetor to the intake manifold of the system at the optimum values during all prevailing conditions of engine speed and load encountered during operation.

The system includes a vacuum amplifier coupled to the intake manifold that responds to a differential vacuum signal developed between the pressures existing at the inlet and throat of the Venturi to produce a proportionally amplified vacuum derived from the intake manifold vacuum. This proportionally amplified vacuum serves to energize the vacuum-motor to shift its axial position in a direction as to bring about a desired fuel-to-air ratio. Not quite that simple to comprehend, but it does offer better control of turbo lag, which leads to better response, improved power and torque output curves, improved fuel consumption and lower unwanted gas emissions.

The new V6 engine management is also assisted by means of high-speed and piezo-resistive cylinder pressure sensors integrated within the engine glow-plugs. These highly developed sensors acquire real-time data from the combustion process for instantaneous fine-tuning of the fuel injection process. In fact this clean combustion control technology will be soon introduced in other GM powertrain diesel engines.

The high-pressure common-rail system allows up to 2000 bar. The injectors are quick-firing piezo-electrically actuated units that allow for up to eight injections per engine cycle. The after-treatment system also includes an oxidation catalyst and a particulate filter close-coupled to the engine to achieve future emissions standards too.

To attain the high outputs, an electronically controlled variable geometry turbocharger for high boost pressures is fitted. Maximum torque is 550Nm at 2000rpm, a figure usually attributed to normally aspirated engines of around 4.5- to 5.0-litres and still providing fuel economy and reduced emissions of an engine of around three litres.

To achieve and maintain such outputs reliably, the new V6 diesel is also imbued with other state of the art technology such as aluminium cylinder heads and a 60-degree V6 bank angle. Another up-to-date feature aiding reliability is the stronger and lighter Compacted Graphite Iron used in the block, which is stronger than aluminium or heavier grey-cast iron. The latter also contributes to a more compact engine. Naturally with downsizing, gains are attained by use of size-reduced reciprocating internal parts that in part is the reason for the more frugal fuel habits and resultant reduction of unwanted gas emissions. The engine has a capacity of 2935cc.

Such is the interest of GM in the field of Green emission controls that it has just reached a joint venture agreement with Penske Corporation to aqcuire a 50 percent equity stake in VM Motori, designers and manufacturers of diesel engines. The latter invention is the main drive in the joint development of the new closed loop control combustion (CLCC) diesel engine.

What should prove interesting is how buyers in the USA will react to a diesel engine. Back in the States the word ?diesel? is almost a swearword. But time will tell, and even though petrol is cheaper, current economic and fuel price rises could easily turn the GM V6 diesel into a popular buy.