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GM Unveils Opel Antara Twin-Turbo Diesel Concept

Antara GTC Twin-turbo

With much fanfare, GM Opel introduced a new 1.9-liter, twin-turbo diesel crossover concept, the Opel Antara GTC at the Frankfurt IAA. Notably absent from the hoopla, however, was the Opel Astra GTC diesel hybrid concept GM had unveiled in January in Detroit. More on this below.

As applied, the twin-turbo, based on the popular 1.9-liter diesel ECOTEC family, dramatically increases the power and torque range of that engine family while maintaining comparable levels of fuel consumption.

The 1.9-liter twin-turbo generates 156 kW (212 hp) of power and 400 Nm of torque from 1,400 rpm—more than twice the power output of the new 74-kW entry-level 1.9-liter CDTI.

GM simulations calculate that the engine, combined with the six-speed automatic transmission, will give the Antara GTC concept a top speed of more than 210 km/h and an acceleration from zero to 100 km/h in around 8 seconds.

GM has been working on the twin-turbo technology for several years, first applying it publicly in an earlier engineering study in an Opel Vectra presented at the Essen show in November 2003. The Vectra—a smaller car than the Antara—used the same size twin-turbo engine (1.9 liters) and produced the same power and torque output, with fuel consumption of 6.0 liters/100km (39 mpg US). GM gave no fuel consumption figures for the Antara GTC.


Opel’s twin-turbo diesel technology. Click to enlarge.

The heart of the twin-turbo technology is forced aspiration of the diesel engine through two exhaust-driven, variable-blade geometry turbochargers, which, unlike bi-turbo systems, operate in series rather than in parallel.

A smaller, highly responsive turbocharger handles the low engine speed range, while a larger turbocharger designed for high output takes over as the revs build up.

This is also unlike Volkswagen’s new production dual-charged technology, in which a supercharger handles low revs and a turbocharger kicks in for higher speed boosting. (Earlier post.) By only using turbochargers, GM avoids introducing the parasitic load of a belt-driven supercharger for low-speed boosting.

The first-stage, small high-pressure turbocharger works alone up to 1,800 rpm and compresses the intake air at up to 3.2 bar boost pressure. Between 1,800 and 3,000 rpm, the larger low-pressure turbocharger kicks in—both chargers run in this speed range. Above 3,000 rpm, only the large turbocharger continues to deliver charge air to the cylinders. The complex control of both chargers is via a valve in the engine’s exhaust system, controlled by engine speed and load.

Where traditional turbo-diesels have a mean effective pressure of 17 to 19 bar, the 1.9-litre twin-turbo reaches 26 bar. The mean effective pressure of an engine is average working pressure acting on the pistons during the combustion process—the higher the value, the higher the power output.

Opel Mid-Range Diesel Engines
kW (hp)
Max. Torque
Fuel cons.
Fuel economy
(mpg US)
NEW 1.9-liter 74 (100) 260 5.7–5.8 40.6–41.3
1.9-liter 88 (120) 280 5.7–5.8 40.6–41.3
1.9-liter 110 (150) 320 5.8–5.9 39.9–41.3
Antara Concept 1.9-liter Twin-turbo 158 (212) 400
Vectra Concept 1.9-liter Twin-turbo 158 (212) 400 6.0 39
3.0 V6 135 (184) 400 6.9–7.0 33.6–34

Depending on the development objective, the twin-turbo can be designed either for high performance or for efficiency in its consumption of fuel. Compared with a naturally aspirated diesel engine, power outputs can be raised dramatically without increasing fuel consumption. (See table above.)

Alternatively, consumption can be reduced by as much as a quarter without loss of power—i.e., downsizing. Opel chose the first route for both its the 1.9 CDTI twin-turbo engine studies (2003 Vectra and 2005 Antara GTC).

Like all Opel’s 1.9 CDTI production cars, the Antara GTC concept is equipped with the maintenance-free diesel particulate filter system (DPF).

As noted above the Opel Astra GTC diesel hybrid concept GM introduced in January along with the Graphyte, GM’s large format SUV hybrid concept, was absent. (Earlier post.)

The Graphyte, by contrast, is prominent at the Frankfurt IAA, which is being heralded as its European debut.

The Astra Diesel hybrid, based on the GM/DaimlerChrysler two-mode hybrid powertrain, used a 1.7-liter turbo diesel engine delivering 125 hp (92 kW) of power and 206 lb-ft (280 Nm) torque with two electric motors, rated at 30 kw and 40 kw, respectively. The diesel hybrid prototype delivered zippy 0–100 km/h acceleration of less than 8 seconds—but with fuel consumption of less than 4-liters/100km (58.8 mpg)—25% more fuel-efficient than the conventional diesel model with the same displacement engine.

At the reveal event for the diesel hybrid, a GM executive made the following observation:

We decided to use a diesel-powered car as a starting point because in the mid-term, we don’t see a demand for gasoline hybrids in Europe. Our state-of-the-art CDTI engines already deliver impressive dynamics and low fuel consumption. The Astra concept demonstrates that fuel efficiency and vehicle dynamics can be significantly improved by hybrid technology.

—Hans H. Demant, GM European engineering vice president and Opel managing director

But the absence of the Astra diesel hybrid from Frankfurt hype, combined with the reveal of the twin-turbo Antara concept implies that GM is focusing on increasing power and maintaining fuel consumption, rather than downsizing for fuel savings.

Although GM’s stated objective for the Antara concept was “to show just how dynamic and athletic an SUV (Sport Utility Vehicle) can now look, with this four-wheel drive Opel concept vehicle,” it could have achieved the goal while making a further statement about improving fuel efficiency. In other words, it could have downsized on the turbo, or continued to work with the hybrid powertrain concepts.

The really interesting concept would have been a downsized twin-turbo diesel hybrid.

Again by contrast, Graphyte was touted as a glimpse at future SUVs—a future that will first appear on the full-size Yukon and Tahoe in 2007.



For a cynical viewpoint, it might be that the motivation of the automakers with this and similar concepts (e.g. VW dual charging) is not fuel saving via down-sizing, but rather to reduce manufacturing and R&D costs by being able to use a single engine design for many different engines. One basic uncharged engine, a mid-range turbo engine and finally a high-end twin turbo / dual charged engine.


I recall Iacocca once saying that having each company building its own engines was a waste of money. He suggested they all jointly own a single engine manufacturing facility which would supply engines world wide. Savings would come from shared engineering and plant economy of scale. We aren't too far from that now.


^^^That comment is retarded!


I don't know why it's retarded. GM should be considering this technology for the U.S. Market, but engineers in Detroit probably won't consider it.

Royse Myers

I am anxious to buy the Opel Astra Diesel Electric Hybrid car, mainly to power it with Biodiesel fuel.
When will it be available? Advise.
Royse Myers


Is this in America? Almost as smart as a 1.8 subaru. :o)

John R. Markert

My '75 Opel Manta had a 1.9 gas engine! Wonderful car!

Bring the Antara to the USA with the twin turbo diesel hybrid and I'll buy it.

Dave Yuncker

I am READY to buy a turbo diesel, but something larger than a VW size car.


The exception that proves the ruleI


Just deserts

terry Walker

trying to find an opel astra diesel hybrid - getting sick of seeing the cars of the future, but never actually seeing them. I can remember looking at these cool cars of the future 30 years ago - where are they? why isn't there a large diesel hybrid market - these cars would kill the competition in efficiency and gas milage? where in the hell is the opel astra diesel hybrid - can't find one for sell anywhere in the world, but see a lot of hype. if the human race doesn't begin to move forward very soon - we will soon become the dinosaurs!
on a serious note - does anyone have any clue how to get an opel diesel hybrid or any diesel hybrid? let me know.

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