Why New Ford V-6 and V-8 Engines Don't Have Direct Injection14 January 2010, 8:58 am
A couple of years ago, General Motors introduced a new-generation 3.6-liter direct-injection V-6—beating its Detroit rivals, and most other automakers, to market with a DI engine. Between the Los Angeles and Detroit auto shows, Ford has introduced a pair of all-new V-6 and V-8 engines, slated for a wide range of applications and the V-6 making more power and torque than that GM V-6. But neither of the Ford engines employ DI.
So, we asked a powertrain expert at Ford, why is this? The answer, surprisingly, is that while we've been led for years to assume that direct injection is always a step ahead for fuel economy and emissions, in many cases it's not—especially when considering cost and complexity, and how the technology will pair with other innovations.
"When the program started, it [the new Duratec in the Mustang] was a direct-injection engine," said Greg T. Johnson, a powertrain integration manager whose responsibilities include both engines. But according to Johnson, Ford powertrain engineers eventually realized that leaving the DI aspect out of the design allowed charge-cooling advantages—allowing engineers to better optimize intake air temps for fuel economy, power, and emissions.
Typically, direct injection allows better control over knock, enabling a higher compression ratio, which does help optimize combustion. "Yeah, it helped us a little bit with knock, but it wasn't that much for all the cost," said Johnson, referring to all the more expensive parts, such as high-pressure fuel-system components, needed for DI. Ford even brought a DI version of the engine through to the point of running prototypes, "but in the end it didn't make business sense," Johnson summed.
The strategy—instead optimizing the new Ti-VCT system and emphasizing breathing—paid off. Having the extra leeway with breathing allowed both engines to put out more power and torque than rival direct-injection engines, while the variable valvetrain boosts efficiency with low load. The new Ford Duratec 37 produces 305 horsepower and 280 pound-feet, while GM's 3.6-liter direct-injected V-6 makes 280 to 304 hp, and 266 to 273 lb-ft, depending on the application.
The new 5.0-liter V-8 in the 2011 Mustang GT likewise has Ti-VCT and some of the same design attributes, according to Johnson (though with a number of racing oriented enhancements we report on here). It also makes more than many same-size or slightly larger V-8s, at 412 horsepower and 390 pound-feet of torque.
Fuel economy, too, is a strong point, with the V-6 expected to yield up to 30 mpg on the highway in the 2011 Ford Mustang and up to 25 mpg on the highway in the 2011 Lincoln MKX (and anticipated for the 2011 Ford Edge). GM's direct-injected V-6 achieves 18/29, at best, in the 2010 Chevrolet Camaro and up to 17/24 mpg in the (admittedly larger) Buick Enclave.
The new 5.0-liter V-8 is also expected to be quite fuel-efficient, with ratings up to 25 mpg highway in the 2011 Ford Mustang GT.
The 2.0-liter, naturally aspirated four-cylinder engine being introduced for the Ford Focus does have DI. According to Johnson, there are no plans to add direct injection to normally aspirated V-6 or V-8 engines, but we will continue to see direct injection in all EcoBoost engines because they are very knock limited and the extra measure of DI helps.
Undoubtedly, it depends who you ask. But maybe DI isn't the very worthwhile upgrade it's often touted to be. Source: The Car Connection