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by Jim Kerr
In the second of a four-part series about new engine technology, Jim Kerr gets a sneak peek at Cadillac’s exciting new 750 horsepower V12 engine shown at the North American International Auto Show in Detroit. Despite prodigious horsepower and torque, this 12 cylinder powerplant achieves the fuel economy of a V8: direct injection and variable displacement technology are responsible.
The rhythmic pounding music faded. The crowd was hushed. A rumble – low pitched, throaty, and insistent – captured everyone’s attention. The wildest-looking Cadillac yet rolled slowly into view. It was the Cien Concept car, propelled by a 7.5 litre, 750 horsepower, V12 powerplant.
Introduced at Detroit’s North American International Auto Show last month, the Cien looks like a cross between a Lamborghini and pure fantasy. Imagine all the sleek, angular sports cars you doodled in school, and the Cien goes one step further. Low, aggressive, mid-engined, rear wheel drive, striking, futuristic, powerful, attention grabbing – the Cien has it all. “I want one” first impressions pull the audience into its mystique. Then there is the sound.
The music of horsepower stirs the blood of any car enthusiast, and the sound of the Cien V12 makes blood boil. Cadillac calls it the Northstar XV12 Concept engine. The all-aluminium, dual overhead cam (DOHC) four valve 12 cylinder not only has 750 horses but puts out 450 ft. lbs. of torque. Being a concept there are no performance specifications but with that amount of power, the Cien is a match for any car in the world. All this performance comes in an engine package that fits in the engine bay and has the fuel economy standards of a modern V8.
While it was difficult to see the mid-engined V12 through the glass engine cover because of the auto show crowd swarming over the car, Cadillac did see fit to have a cutaway model of the engine on display for a short time later in the day. I took a good look and found lots to see.
The aluminum alloy block looks like it is a production unit, complete with reinforcement ribs, mounting points for accessories, and casting numbers. Sure it had been detailed and painted nicely, but this looked like it was ready to slip into an engine bay rather than just a concept. A deep-skirted block is used to solidly support the crank, and a cast alloy oil pan finishes it off. Aluminum heads featured four valves per cylinder, two chain-driven camshafts for each head and variable camshaft timing. Much of the cylinder head technology looks similar to the current Northstar V8 engine, although it is definitely different in dimensions.
Getting air into the engine is accomplished through a high flow plastic moulded intake manifold, while the exhaust passed through swoopy stainless steel headers. Large drive-by-wire throttle plates control the flow. All this is not new technology, just good old-fashioned performance savvy any hotrodder would be proud of, but here it is adapted with modern materials and methods.
Fuel economy for a 7.5 litre engine with this power should be terrible, but Cadillac has used two technologies to bring it into line. First, there is direct injection. Gasoline injection typically sprays the fuel into the intake port, where it sits waiting for the valve to open before it flows into the cylinder. With direct injection, the fuel is sprayed directly into the cylinder, so combustion efficiency and fuel economy is improved. Lubrication of injectors in a high pressure, high temperature environment has always been a durability issue, but there are a few engines in the world that are using this technology. I predict we may soon see it in the showrooms in North America.
Variable displacement, or "Displacement on Demand" as GM calls it, is the second technology used to enhance fuel economy. The Northstar V12 can run seamlessly on one bank (six cylinders) when power is not needed. Step on the throttle and extra cylinders cut in for added power. Displacement on Demand has been used in prototype GM trucks, and it has been announced it will see production in select SUV's by 2004. Cadillac tried this concept in the 1980's with terrible results, but today's computing power, materials, and fuel systems are light years ahead of then. Now the system works smoothly and seamlessly.
Last but not least, the Cien has integrated the starter and generator into one unit for space and weight savings.
Rumours abound when concept cars are shown, and one rumour is that Cadillac has over 150 of the V12 engines in various stages of testing. Sounds more like a production unit than just a concept.