Not their finest hour: Cadillac V-8-6-4

Celebrating the greatest cock-ups in automotive history. This week we look at the Cadillac V-8-6-4
By Sony Thomas, Deputy Editor
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November 07, 2016
NTFH Cadillac

Cylinder deactivation isn’t a novelty anymore. Known as variable displacement, multi-displacement system, and active cylinder control, this technology is now commonly in use in cars made by most of the major carmakers, from General Motors and Chrysler to Mercedes-Benz and Bentley. But this isn’t a modern innovation, as it was first used in an automobile called the Sturtevant 38/45hp way back in 1905. That car had a six-cylinder engine, of which three cylinders could be stopped to increase fuel efficiency. It was also used in the 1917 Enger without much commercial success.

So when General Motors came out with the L62, more popularly known as the V-8-6-4 engine, in 1981 to power its Cadillac models, including the Eldorado, it was just reviving an old idea. And there was nothing wrong with the idea. However, like many things GM tried in the period, its execution was far from perfect. Dubbed ‘modulated displacement’, the system relied on solenoid deactivation of the rocker arms on two or four of the 6.0-litre V8’s cylinders. In theory, this meant fewer cylinders would be fired if the engine load was low, so it would be a V8 at full throttle, a V6 at medium load, and a four-cylinder when cruising along.

However, this seemingly great theory did not translate well into practical use.

While the mechanicals of the V8 were robust, the on-board computers of the time were not advanced enough to cope with the speed with which these transitions had to be made. So, in real world use, the shifts between four, six and eight-cylinder modes were anything but smooth, and as Cadillac owners found to their dismay, the engines shuddered every time the system was activated, with some of the engines even stalling as a result. Soon, disgruntled owners started taking their cars back to Cadillac to get the system disabled. This led GM to abandon the technology in most of the Cadillacs just one year after its introduction. However, the damage had already been done, and the fiasco put a sizeable number of customers off the Cadillac brand forever.