The Ward’s 10 Best Engines competition has recognized outstanding powertrain development for 16 years. This month, Ward’s explores the history of GM’s direct-injection 2.4L Ecotec I-4.
Like the late sad-sack comedian Rodney Dangerfield, 4-cyl. engines “don’t get no respect.”
Yes, they typically are less expensive and more fuel efficient than V-6s, but they also too often fall short when it comes to passing power or hauling heavier loads. They also frequently have noise, vibration and harshness issues.
That’s why few 4-cyl. engines that are not diesel, turbocharged, supercharged or part of a hybrid-electric vehicle powertrain seldom have been honored by Ward’s editors with a 10 Best Engines trophy in the 16 years of the competition.
That is, until now.
A quick count of this year’s 10 Best Engines award winners reveals no fewer than six 4-bangers: two turbocharged, two HEVs, one diesel and even one naturally aspirated, workaday 4-cyl. engine –Co.’s 2.4L Ecotec.
The history of the Ecotec 4-cyl. family goes back to the late 1990s. It started as a joint program with U.S. and European GM engineers working with (and based at) Lotus Engineering in the U.K.
The project was aimed at developing a global 4-cyl. that took advantage of all the knowledge GM had around the world, says Ecotec global chief engineer and program manager Chris Meagher.
“Back then, we (in North America) were far from being experts on 4-cyl. engines. We focused mostly on V-8s and V-6s. The opposite was true in Europe. So we made sure we took into account all the knowledge and resource capability we had to develop that engine,” Meagher says.
The first was the 2.2L port-injected version launched in the U.S. in late 1999 for the ’00 model year.
The family has since grown to include a 260-hp turbocharged 2.0L introduced on the Pontiac Solstice GXP, Saturn Sky Red Line, Chevy Cobalt SS, and HHR SS; a 2.4L PFI offered on the Chevy Malibu and other midsize cars; and the new 182-hp 2.4L DI engine that debuted as standard equipment in the ’10 Chevy Equinox and GMC Terrain cross/utility vehicles, Buick LaCrosse and upcoming Regal sedans.
“The goal was to produce a world-class 4-cyl. engine,” says Meagher. “We knew that moving forward into the new millennium, fuel economy would be a bigger and bigger issue. If we were going to be a serious player, we would have to have a world-class four, not just for North America, but globally.”
Meagher defines “world class” as “The best, or at least fully competitive, in all key functional parameters.”
Direct injection is what makes this engine unique relative to high-volume competitors in its size and price class.
“I think we are pretty early out there in applying that technology to a higher-volume engine,” he says.
“We started in 2004 on a (Europe-only) low-volume 2.2L and then applied it to the 2.0L turbo. And as we wanted to expand it further, (the U.S.) became a great home for it, because this displacement (2.4L) is used in a lot of midsize cars and smaller crossovers.
“We knew the benefits in terms of power, fuel economy and emissions made it a worthwhile technology to apply at higher volumes. And we knew we had to make that kind of improvement to keep up with both fuel-economy demands from our customers and regulatory requirements, such as corporate average fuel economy.”
Plus, there is room for future efficiency improvement as CAFE grows more strict in coming years.
“I think we have somewhere between another 5% and 10% that we can still squeak out of it,” Meagher says.
GM engineers are targeting three main areas: thermal efficiency, mechanical efficiency and friction.
“I think the mechanical area probably has the biggest bang for the buck right now, trying to figure out ways to reduce energy lost in the pumping loop, for example,” Meagher says. “One way of doing that is variable-valve lift, not unlike what some of our competitors already do.”
Like its less-refined cousins, this smooth, quiet, and fuel-efficient DOHC, 16-valve 2.4L benefits from variable-valve timing (VVT), or “cam phasing,” as GM calls it, on both intake and exhaust sides.
“We had a lot of data from prior applications,” Meagher says. “So we knew we were going to succeed in efficiency, and final calibration and vehicle configuration would determine what power and torque we were going to see.”
NVH was the biggest challenge.
“We always are working on getting our Ecotec family quieter and quieter,” he says. “If someone told me it is quiet today, I’d say, ‘Yeah, but we can do better.’ We have some base engine noise that we want to take care of. (Noise from) the high-pressure DI is a challenge, and our suppliers recognize that and are working on it as well.
“But we wanted to make sure we were looking at the whole picture, not just one subsystem, so we took the opportunity to change from the lost-foam block casting that we’ve used on the Ecotec family since the beginning to a precision sand-cast block supplied by Nemak S.A.
“It’s a different casting technology that provides a little better structure, and when you have better block structure, you can avoid the internal noises that emanate from the engine like a drum.”
It is slightly more costly, he admits, but also provides better porosity characteristics.
Meagher says GM engineers also spent a lot of time and effort with supplier Hitachi Automotive Products Inc. to come up with a suspended injector and an isolated fuel rail.
The injectors have a clip and plate connection into the injector cups on the rail, and two Teflon seals center them in the cylinder head openings so they do not actually touch the head. The rail has two rubber grommets and compression limiters that isolate it from the cylinder head mount.
The whole system is isolated as much as possible from the rest of the engine.
“If you let it touch the engine, all those injector openings and closings and fuel pump firings and pressure waves in the rail will be transmitted through the head to the rest of the engine, and those sound waves will emanate from the engine all over the place,” Meagher says.
There also is foam stuffing behind and under the intake manifold and a foam cover on the cam-driven high-pressure fuel pump. The Equinox/Terrain also uses active noise cancellation to prevent exhaust-pulse vibrations from being transmitted into the cabin.
“In the Equinox,” Ward’s editors raved, “this engine never fails to delight with ready throttle response and strong mid-range acceleration.”
Several were “astonished to achieve 30 mpg (7.8L/100 km) in the Equinox in mixed driving, without babying it.” And we’ll bet some, if they had not known it was a 4-cyl., might have mistaken it for a V-6 as many other reviewers have.