Cadillac takes another look at its 3-in-1 engine

The future of Cadillac's V-6-8-4 engine is in doubt. "As we downsize the cars in 1983 we don't need that big an engine," asserts Edward C. Kennard, general manager of Cadillac.

The modulated (variable) displacement of 6-8-4 system, an exclusive with Cadillac this year, is used on the big gasoline-fueled engine but not the Buick-built V-6. The Cadillac-produced engine is really three engines in one, depending on the load on the engine -- whether the car is picking up speed, climbing a hill, etc.

If the load is light, the car moves along as a "4," even at a slow speed on a level road; then if the load goes up, the car shifts automaticlly to an "8." The engine resorts to a "6" only if the car is moving at 47 miles an hour and up.

"Why did the V-6-8-4 to avoid the gas-guzzler tax," asserts Mr. Kennard frankly. If a car fail to check out a 17 miles per gallon on average for '81, the car buyer pays a tax. Next year the bae mpg is 18 1/2 and the tax figure goes up.

Ford tried to make the system work on a 6-cylinder engine which was designed to switch down to a "3." That was too big a transition, engineers muse. Also, the use of a microprocesor enabled Cadillac to do thejob a lot more smoothly than Ford could do with a system which relied on a carburetor.

Still, the new Cadillac exclusive may bite the dust.

"We're now struggling over whether or not to carry over the 6-8-4," Mr. Kennard reports.

For one thing, Cadillac engineers say they are going to have a hard time getting it to where it will get 18 1/2 mpg in 1982 as the gas-guzzler law requires. Also, the division will have a new smaller-displacement engine by then which will meet the letter of the law.

"Of course, we can modulate the new engine," says Mr. Kennard. "But if we start with a 4-liter engine as an '8,' it would be 3 liters as a '6,' and 2 liters as a '4'.

"We don't know whether a 2-liter configuration would do the job."

The current engine is 6 liters as an "8," 4 liters as a "6," and 3 liters as a "4."

The current engine is 6 liters as an "8," 4 liters as a "6," and 3 liters as a "4."

Cadillac plans to build a new car-assembly plant, including and engine line, in Detroit but so far has failed to get the required go-ahead from the city. The new facility would replace Cadillac's aging operation nearby.

The 6-8-4 equipped Cadillac is a fun car to drive. Clearly, you can't expect import-car mileage in a Cadillac. Even so, with the variable-displacement power plant under the hood, the average mpg, with the engine in 4-cylinder mode, runs up to the high 20s. But when the rest of the cylinders jump into play, the mileage falls off fast.

A digital display board on the dash tells whether the engine is operating as an 8, 6, or 4.

"It makes a great demonstration tool for our salesmen," smiles the Cadillac division chief.

Mr. Kennard adds: "It created a lot more excitement about our cars than I had anticipated."

Surprisingly, it's almost impossible to tell when the engine shifts from one mode to another. The transition is that smooth.

The new Cadillac are a marvel of electronic wizardry which, among other things, adjusts the spark advance continuously, signals when something is wrong in the engine, and even diagnoses itself as an aid to the mechanic. A digital display panel tells the average fuel economy at the moment, the average for the trip since the reading was the last reset, and the estimated distance to an empty fuel tank based on the current rate of fuel use.

It's all in the computer under the hood.