[Shotimes] (OT) Engines Go Back to the Future - NYT

[Ron Porter]

FYI,

An article that will be in Sunday's NYT.

Ron Porter

December 4, 2005

Engines Go Back to the Future
 
By CHERYL JENSEN

GERMAN automakers gave up pushrod engines long ago, in favor of more complex
overhead-cam power plants. The Japanese have essentially quit making the
old-design engines. Ford is down to just a couple.

But Chrysler, with seven, and especially General Motors, with about a dozen
in 21 different forms, remain bastions of the pushrod engine, also known as
an overhead-valve design. 

Not only has G.M. continued to carry forward older engine designs, like the
famous "small block V-8" in your grandfather's 1955 Bel Air (and your son's
2005 Corvette), it has been designing new ones. The Chevy Impala offers two
pushrod V-6's that are new for 2006.

G.M. says the new engines share almost nothing with the old ones. The
Impala's base engine, a 3.5-liter V-6, was actually developed from the more
powerful 3.9 V-6; the two share more than 80 percent of their parts.

While the Impala's powertrains may seem caught in a piston-pushing time
warp, the new-old engines were designed with innovations like variable valve
timing, which provides a broader power range and produces lower emissions. 

Further, G.M. and Chrysler say that pushrod engines lend themselves better
than overhead-cam engines - the two companies make plenty of those, too - to
another bit of fuel-saving technology that is becoming popular: deactivation
of half the cylinders at cruising speed.

But money is a big factor in G.M.'s back-to-the-future powertrains. Brett
Smith, director of product and technology forecasting for the Center for
Automotive Research in Ann Arbor, Mich., said the company saved an estimated
$800 a vehicle by sticking with pushrod motors, which cost less to make
largely because they contain fewer parts. Dollars saved on the engines can
be used to add other features to the cars.

Some enthusiasts defend pushrod engines, which usually have two valves per
cylinder (rather than the three or more valves common among overhead-cam
designs) for their strong low-end thrust. 

A potentially bigger deficiency of the new Impala is its four-speed
automatic transmission; competitors have five or six speeds. Additional
gears can improve acceleration and fuel economy. G.M. is working on
six-speed automatics for front- and all-wheel-drive cars, but they were not
available in time for the 2006 Impala.