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GM Introduces New V-6 Clean Diesel; Engine will Debut in Cadillac CTS in 2009 in Europe

The new GM V-6 diesel. Click to enlarge.

General Motors has unveiled a new 2.9-liter V-6 turbodiesel engine with advanced injection and combustion technology for low emissions and high performance.

The new 184 kW (250 hp) engine will be sold mainly in Europe and makes its public debut this week at the Geneva Motor Show (8-18 March). Its first production application is scheduled for 2009 in the new Cadillac CTS.

The compact dual overhead cam, four-valve V-6 engine belongs to a new GM family of diesel engines, featuring an innovative closed-loop combustion control system designed to meet future emissions standards. The engine can be installed in a longitudinal or transverse layout and can be adapted to a wide range of two- or four-wheel-drive vehicles.

GM worked with Ricardo on developing an advanced diesel engine control (ADEC) system designed to enable consistent achievement of very low emissions levels through closed loop control of the combustion process. The ADEC coordinator uses a range of sensors to measure combustion states and then establishes the optimal balance of fuel quantity and timing and air path control. (Earlier post.)

GM’s development of the new engine is being coordinated under the leadership of GM Powertrain’s European operations in Turin, Italy, in cooperation with VM Motori based in Cento, Italy. GM Powertrain will focus on the development of the clean combustion process, electronic engine control and exhaust-gas aftertreatment, as well as calibration and integration into GM vehicles. VM Motori will build the new unit at its plant in Cento, Italy, and is responsible for the mechanical aspects of the engine’s design, development and bench testing.

The V-6 engine management system enables optimal fuel economy as well as reduced emissions and noise by using a recently developed combustion control technology. Key enablers of the system are high-speed, piezo-resistive cylinder pressure sensors that are integrated within the engine glow plugs. These specialized sensors acquire real-time data from the combustion process, enabling instantaneous fine-tuning of the fuel injection process. In the future, this clean combustion control technology will be introduced in other GM Powertrain diesel engines.

A future version of such a closed loop combustion control (CLCC) system with cylinder pressure sensors will likely be an enabler of HCCI combustion regimes.

The high-pressure, common-rail system provides up to 2,000 bar (29,000 psi) injection pressure. The injectors are quick-firing, piezo-electrically actuated, allowing up to eight injections per engine cycle. The aftertreatment system includes an oxidation catalyst and a particulate filter that are close-coupled to the engine to achieve future emissions standards.

An electronically controlled variable geometry turbocharger generates boost pressure. The engine has a torque of 550 Nm (406 lb-ft) beginning at 2,000 rpm, while providing effective fuel economy and reduced emissions.

The new, compact V-6 powerhouse features aluminum cylinder heads and a 60-degree bank angle, 83.0 mm bore and 90.4 mm stroke, which results in displacement of 2,935 cubic centimeters. The engine block is made of stronger and lighter Compacted Graphite Iron (compared to lower-strength aluminum or heavier grey cast iron) to optimize engine packaging, weight, refinement and performance.



Bud Johns

Very impressive. State of the art in every respect, and look at the whopping power for the displacement! They need to rapidly expand this technology to all of thier diesels..........


Very impressive -- I agree -- Is it bio-diesel compatable? If it is then "Now we're moving forward".


Yippee- yet another Europe-only diesel!

I have been waiting since '97 for the arrival of clean, common rail diesels in the US market. Now that ULSD is here, what is taking the car manufacturers so long? As far as I can tell, only Daimler, VW, and Honda are close to bringing TDI's to our market.

Could the big 3 be missing yet another chance at market leadership?


GM: Bring this diesel to America and install in Cadillacs, Chevrolet Malibu, Buick Lucerne, Lambda platform crossovers, and oh what the heck, how 'bout the Saturn Aura too. You'll sell a bunch and be greener to boot. Just be sure the bugs are worked out.

By the way, my advice is free for now, although I'm strongly considering raising my rates. Get it while it's still a bargain!!!


This sounds like it would make a fine powerplant for a truck. All there is right now is HUGE diesel engines or slightly smaller gasoline guzzler engines.


I agree with Schmeltz. If they market this in Europe they face all sorts of diesel competition. And they are an American brand. So how much market will they get?

In the US there is almost no market for diesel cars but everyone knows it is going to build up fast. So Cadillac can start even with competitors here.


I bet GM wants to see how Mercedes Diesels sell in the US. If they have market acceptance, then they will launch a Cadillac with a diesel in the US. Otherwise it is more likely to see diesels reserved for truck based SUVs and trucks in US GM vehicles.


GM sells Cadillacs in Europe!!!! Oh, so that's what European pimps drive.


They might be holding back because of the price of diesel. Out here in Phoenix, its running a good 30¢ or so higher per gallon than regular, and a diesel power train costs more than a gasoline engine, so its hard to make back your investment, and here, price is king.


I know what you mean about making back your investment. I'm still trying to make back the investment on my 32" LCD TV versus the 32" CRT I almost bought (just 10 more years of TV watching to make up the difference in electricity saved vs. price!).

I'm still trying to make back my investment on the dual core processor I purchased (but that seems to have me spend more money on more advanced games) as well.

Maybe I should stick to mutual funds, real estate, and bonds for my investments and just keep the rest of it as either entertainment or a mode of transportation and seek to minimize the amount of energy I consume in the pursuit of entertainment and transportation.


Don't forget that diesel cars that meet at least Bin 5 will be eligible for a tax credit in the U.S. That should at least partially offset the higher initial cost (assuming, of course, that the manufacturers don't raise the price of diesel vehicles by an equivalent amount).


March 2007 issue of Scientific American has an article on clean diesel. Here is an excerpt on Honda's technology that might interest greencarcongress readers.

Several basic approaches to de-NOx systems exist, says Ben Knight, vice president of R&D for American Honda. One is known as continuous hydrocarbon selective catalytic reduction. This method involves running the diesel engine rich to place hydrocarbons in the exhaust stream, where they work with a catalyst to chemically reduce NOx--that is, to ready the NOx for conversion into nitrogen gas by adding an electron in a partial reaction. The method has cut NOx output by as much as 40 percent during certain European test driving cycles but also adds a 5 percent fuel penalty, which is not considered cost effective. In addition, it yields lower conversion efficiency at low temperatures.
Honda recently announced an elegant new approach to de-NOx technology, a lean-NOx catalyst that demonstrates NOx conversion rates of 90 percent yet requires no added reducing agents. This innovative technique converts some NOx into ammonia and then recombines it with the remaining NOx to make nitrogen gas. The prototype process, which was developed by a team led by chief engineer Hiroshi Ohno, is expected to first appear in a diesel-powered 2009 Honda Accord. according to news reports.
The Honda system centers around a compact dual-layer catalyst, Knight says. The top layer contains zeolites, micro-porous materials that act as high-surface-area, solid-state acid substrates that facilitate chemical reactions. THe bottom layer incorporates two other common catalysts, cerium oxide and platinum.
"During normal lean engine operations," Knight explains, " the top layer simultaneously absorbs incoming NOx and converts part of it into nitrogen. In the brief periods when the diesel is set to run rich, the bottom catalytic layer generates ammonia from the exhaust gases. But rather than passing this ammonia directly back into the flow, it is stored in the upper layer's zeolite substrate until the engine flips back over to lean-burn, at which point the ammonia reduces the NOx into nitrogen gas." The lower layer forms ammonia in two ways: it chemically combines ambient NOx and hydrogen to yield the compound ammonia, and it also performs what chemists call a water-gas shift reaction with carbon monoxide and water vapor to form ammonia. Because the NOx storage burden is lessened (compared with other methods), he says, there is less NOx to trap during lean operation, which keeps the system compact and cuts down on rich operation time, thereby lowering fuel penalty.
Knight emphasizes that the lean-NOx catalyst's advanced control system is important because it determines how much ammonia is made. The controls realize this goal by monitoring and modifying the engine operation to set the durations of its lean and rich periods. "The controls are adaptive and optimize the system even if the catalysts degrade over time," Knight says--a key to enabling future Honda diesels to achieve EPA Tier 2, Bin 5 output over the required 125,000 miles of driving.


Any ideas whether these diesels would be useful in smaller motor homes? Class C types for instance.

If so, how long before they make their way into the Winnies, Tiogas, etc...?


Okay, GM.

You've got a near-world-class car in the form of the Saturn Aura (in my opinion, let down only by the powertrains, which use too much fuel - I like the rest of the car).

Take that engine, put it in the Saturn Aura, with a good efficient transmission, and you might yet get me to buy one.

My current vehicle is a VW Jetta TDI, and I have no intention of ever buying another gasoline (or E85) guzzler.


4-5 cylinder (1.2->2.4-liter) versions of this engine should be adequate for B-D (subcompacts-midsized) segment cars. The 2.9-liter V6 should be reserved for luxury/performace models.


My thoughts exactly Allen...BTW this V6 engine has a timing chain, something these engines should not be without as the reliability of cambelt V6s esp diesels has been dubious.


If this could fit in the H3 it would make a great alternative to the atlas I5. More power, more torque and I'm guessing much better mpg.

Rafael Seidl

Argod -

I think Honda may be quoting results based on the Japanese driving cycle, which features notoriously low engine loads and hence, low exhaust temperatures. Since SCR requires at least 250 degC at the catalyst, that means they have to inject late to artificially raise the exhaust temperature and end up with a 5% fuel economy penalty. Even that is not enough much of the time, which is why they only get a 40% conversion rate.

With a US or European driving cycle, exhaust temps are naturally higher and conversion rates are much higher. Moreover, there is little or no need to artificially raise exhaust gas temperatures, especially if the vehicle also features idle-stop technology. The fuel economy penalty is therefore much smaller than 5%. The urea consumption is about 4% of the diesel volume flow, but here in Europe it only costs half as much, which is why HDV suppliers have mostly picked SCR over high-EGR concepts to meet Euro 4 emissions.

Honda's approach of producing ammonia catalytically from part of the NOx coming out of the engine to neutralize the rest of it is elegant- However, the conversion capacity in part load operation is quite limited so you need to run the engine in HCCI mode, which opens another can of worms. Honda may well have mastered this trick and be the first to put it into production but there will be a price tag attached. Also, common sense will tell you that reducing NOx to NH3 takes free hydrogen and energy, so those have to come from somewhere.

The Honda system's key advantage over SCR is that it does not require an additive that needs to be replenished. The presumed key advantage over NOx store catalysts is that the device is not nearly as sensitive to sulfur in the fuel and, that you don't ever need to run the engine rich (which clogs up your DPF that much faster).


The concept seems brilliant, allowing the engine to optimize itself through real time in-cylinder feedback. This technology has the possibility for rapid adoption by the industry. With nearly twice the performance of a typical passenger diesel engine design of only a couple years ago, the use of only 2 of the cylinders from this clean diesel would suit A-C segment vehicles. Why not a horizontally opposed 978cc making 61kW (83hp) at redline and 183Nm (135lb-ft) at 2000rpm? It would do something like 0-100km/hr in 10-12 seconds. Drop in a bank of affordable, advanced, lead-acid batteries into the engine compartment to add a rational level of hybridization.

Rafael Seidl

JC -

two-cylinder engines suffer from high torque variation over the course of two crankshaft revolutions because the pistons only produce power during half that time. Inline twos also suffer from free inertial forces of the first and second order, though these would admittedly be less serious in a diesel than in a high-revving gasoline engine.

Three cylinders is therefore generally considered the minimum for A segment cars sold in Europe, with manufacturers switching to an inline 4 rather than adding a compensation shaft once you get above ~1000cc.

Separately, the closed-loop control of the V6 engine discussed in the article does not yet include in-cylinder pressure gauges. In other words, the loop is closed from one cycle to the next (at best) rather than within a single cycle.

Beru and others offer glow plugs with built-in quartz transducers but they are still too expensive and finicky for series production vehicles. Something like that will be necessary for concepts featuring some variation of HCCI combustion in part load, something a lot of diesel researchers are working on because the low exhaust temperatures in that part of the engine map make it more difficult to clean up the NOx using an aftertreatment system.

Spokane Walt

To all the people asking GM to bring this engine to the USA - I have a better Idea - just bring the existing Diesels that GM is selling in the Vauxhall and Opel Brands in Europe - in fact just move the steering wheel to be left hand driver and brign the whole vehicles!

Check out These are nice fuel efficient vehicles - can you say mini-van that gets above 30MPG?


Currency exchange being what it is, GM and others should be making these engines here and maybe even exporting.


I'm tired of our country supporting companies that make tens of billion in profits and that thug Hugo Chavez (Citgo). We need a galvanized electorate demanding a biofuels revolution from our elected officials. Biofuels NOW!

Jeff Conforti

I have a 2006 Diesel Jetta, a 2007 Diesel ML320 TDI and a 2006 HyHy (Hylander Hybrid). GM needs to make small, fuel efficient diesels available here for cars and the Tahoe and Suburban. You can have a big diesel for the Suburban for those that need to tow something but the rest of us need it for our SOCCER WIVES to drive all the kids around and to go to Home Depot. By the way GM, DO NOT skimp on the engine quality. YOU HAVE ONLY ONE CHANCE AT THIS!!!!!!

Ray Chuang

I wouldn't be surprised that GM offers this new Tier 2 Bin 5 compliant engine in the USA market on a number of models (can you say GMC Acadia/Saturn Vue/Buick Enclave?). A smaller I-4 turbodiesel based on this new technology could be extremely attractive on something like the Chevrolet HHR.

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