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GM Hooks Up With VM for New Cadillac Diesel

The new engine will get its first application in the European-market ’09 CTS sedan and features what GM says is the first use of closed-loop combustion technology.

PONTIAC, MI – General Motors Corp. is reconfirming its commitment to diesels, Cadillac and the European market with a new 2.9L V-6 oilburner that will bow in the ’09 CTS sedan.

The auto maker is taking the wraps off the new powerplant, which was designed in Italy with VM Motori SpA, at the Geneva auto show today.

GM isn’t revealing too many details of its development deal with VM but says the engine uses GM Powertrain technology and will be built by VM at its plant in Centro, Italy.

The deal allows VM to sell the diesel to other auto makers, but officials aren’t indicating whether the supplier already has lined up additional customers. VM Motori is owned 51% by Penske Group and 49% by DaimlerChrysler AG. It supplied the diesel for the Jeep Liberty in the U.S., but that engine was dropped from the lineup for ’07 because it didn’t meet tougher emissions standards taking effect.

GM won’t forecast expected volumes. But the new sequentially turbocharged diesel will appear first on ’09 CTS sedans sold in Europe and eventually make its way under the hood of unspecified Opel, Saab and Vauxhall vehicles. It will launch in longitudinal form, but also is designed for transverse applications.

For the CTS, engines will be shipped from Italy to GM’s Lansing (MI) Grand River plant where the CTS is assembled, and the finished cars will be exported to Europe.

Although it is capable of modification for sale in the U.S., GM says it has no plans to offer the engine here due to unfavorable market conditions.

The new, sequentially turbocharged, direct-injected 2.9L V-6 is critical to GM’s strategy of continuing to build more than 1 million diesels annually and key to meeting future demand in Europe, where diesels are expected to remain dominant in the market.

GM projects DI diesels with sequential turbocharging – two turbochargers positioned in a series – will achieve more than 50% market penetration in Europe in 2014 as auto makers look to boost power and meet tougher emissions standards.

The all-new engine, which has been in the works with VM Motori since a development deal was signed in July 2005, is rated at 250 hp at 4,000 rpm and delivers 406 lb.-ft. (550 Nm) of torque at 2,000 rpm. Precise displacement of the 60-degree, dual-overhead-cam, 24-valve engine is 2.935L and compression ratio is set at 16.5:1.

Key to the new diesel is its closed-loop combustion technology, the first use of such a system at GM and what the auto maker believes is the first application industry-wide.

The system uses the engine controller to adjust injection pressure and timing based on real-time pressure measurements inside each cylinder. Those readings are relayed by piezo-resistive sensors integrated within the engine glow plugs.

The controller adjusts the fuel-injection events as needed to provide a consistent pressure curve and limits the amount of over- or under-fueling that can occur, GM says. This lessens oxide of nitrogen emissions up to 90% compared with Euro 4 standards, while avoiding any fuel consumption penalty as a result.

Weight and size are reduced through use of compacted graphite iron for the block and bedplate and aluminum for the cylinder heads.

The unit employs an electronically controlled variable geometry turbocharger and piezo injectors along a common rail that are capable of producing as many as eight injections per engine cycle at pressures up to 29,000 psi (2,000 bar).

A close-coupled oxidation catalyst, particulate filter and exhaust-gas recirculation, combined with the closed-loop combustion system, help the diesel meet Euro 5 emissions standards that take effect in 2009.

A high exhaust-gas recirculation rate of up to 65% enables highly pre-mixed combustion in low load conditions, limiting NOx and particulate emissions.

GM says the engine is class leading when it comes to limiting noise, vibration and harshness.

To offer the diesel in the U.S., the auto maker says it would need to meet Tier 2 Bin 5 standards that also take effect in 2009 and are six times more stringent on NOx than Euro 5. In addition, it would have to meet California LEV II requirements, which are even more aggressive than the U.S. targets.

Further limiting its chances for U.S. application, the engine’s software would have to be upgraded to achieve OBD II onboard diagnostic standards, a “considerable step,” Charlie Freese, executive director-GM Powertrain diesel engineering, says at a pre-show backgrounder here on the new diesel. The engine also would need modifications to its aftertreatment system in order to hit the tougher NOx targets.

While technically possible, Freese says the cost-benefit equation currently is too tough to solve in the U.S. for midsize cars such as the CTS.

Given current diesel fuel prices, most American buyers wouldn’t drive their cars long or far enough to realize a payback, he says. That’s why in the U.S. GM is focusing more on diesels for bigger pickups and SUVs, where the investment payback is quicker.

Still, Freese says even though the engine wasn’t engineered to U.S. specifications, GM “wouldn’t develop a new engine without an eye to future (application) growth.”

The new diesel is not part of a larger family that will feature multiple displacements, Freese says, but the GM-developed combustion process and other aspects of the engine could make their way into other diesels.

In addition to the combustion process, GM is responsible for the exhaust-gas aftertreatment system and the calibration and integration of the diesel into its vehicles. VM, along with building the unit, is responsible for the mechanical aspects of the engine design, as well as testing.

Freese says GM tapped VM for the project because the auto maker’s own engineering resources were stretched thin and VM’s flexible manufacturing facility was better equipped to build the diesel.

The new powerplant brings to at least eight the number of diesels that will be offered by GM worldwide after 2009. The list includes four 4-cyl. diesels ranging in displacement from 1.3L to 2.0L and output from 90 hp to 150 hp, the 180-hp 3L V-6 DCTi and the 365-hp 6.6L Duramax V-8.

Also in the count is a new cleaner, compact, high-efficiency V-8 diesel due after 2009 for light-duty trucks that GM detailed back in August. The new DOHC, 32-valve turbodiesel will package into the same space as a small-block V-8 gasoline engine, GM says, and improve fuel economy for light trucks by 25%.

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