When gas prices were rising in the 1980s, Cadillac said it solved the problem of obtaining better mileage from big cars, which was significant at the time because Cadillac specialized in big cars.
The answer was displacement-on-demand (DOD), or a V-8 engine that could operate on 8, 6 or 4 cylinders so it could offer power and fuel economy in the same car.
The experiment failed because the Cadillac V-8-6-4 didn’t have a computer sophisticated enough to determine when it should be in 8-, 6- or 4-cylinder mode and juggled between them with a distinct engine thump.
Now comes Chrysler with a variation of DOD called multiple displacement system, or MDS, which allows the engine to run in 8- or 4-cylinder mode depending on whether you need power or want higher mileage. The computer sensors are much more sophisticated and the operation is seamless, with no thumping.
“We were well aware of the Cadillac experience with the V-8-6-4 and figured after 20 years we had one chance to do this without shooting ourselves in the foot,” said Alan Falkowski, MDS product engineering team leader for Chrysler. (GM, it should be noted, is going to give the system another try starting with the 2005 Chevy TrailBlazer EXT that comes out this fall.)
While others have gone the gas/electric route to conserve fuel, Falkowski feels comfortable with shutting down 4 cylinders.
“MDS adds about 7 percent to the cost of an engine, a tiny fraction of the cost of a hybrid. This technology costs hundreds, hybrids cost thousands,” he said.
With MDS the 5.7-liter Hemi V-8 in the ’05 Chrysler 300C sedan and Dodge Magnum R/T gets 17 m.p.g. city/25 highway mileage.
Doesn’t sound like much, but without MDS the rating would be 15 m.p.g. city/22 highway and cost consumers a $1,000 gas-guzzler tax for failing to obtain 22 m.p.g. in combined city/highway driving, Falkowski said.
But if 17/25 is possible, why not a little more?
“We could extract more mileage and haven’t gotten the maximum benefits of MDS yet. It now idles in 8-cylinder mode, but we could have it idle in 4-cylinder mode, though that would mean some noise and vibration idling at a stoplight,” he said.
Or, he said, “We could add some new technology.”
Though he refused to say what technology, have to suspect he means having the engine shut off rather than idle at the light and then restart when the gas pedal is pressed.
No word on how soon new technology such as engine shutoff might be added to the Hemi V-8, but Falkowski notes that “as gas prices go up, there’s more incentive.”
Chrysler also is evaluating the use of MDS in other engines.
“The bigger the engine, the bigger the benefit. We have a V-10 in the Dodge Viper that would be feasible to run with 5 cylinders, but those who buy a Viper aren’t concerned about fuel economy,” he said.
“What you might see instead is bigger engines with MDS in smaller cars for added performance without fuel-economy penalties, such as a V-6 in a Neon-size car,” he said.
To ensure MDS succeeds, Falkowski said all warranty parts on the MDS Hemi V-8 are restricted, meaning no repair parts are sent to the dealer until his service staff calls Chrysler engineers to report symptoms and pinpoint problems to spot trouble quickly.
But Falkowski said there’s an easy way for him to judge how well his MDS system succeeds.
“I will have done my job if in the future the newspaper ads listing used MDS cars for sale don’t say: `Engine replaced.'”
———-
Read Jim Mateja Sunday in Transportation and Wednesday and Friday in Business. Hear him on WBBM-AM 780 at 6:22 p.m. Wednesdays and 11:22 a.m. Sundays.
