GS69

Why New Ford v6 & v8 Engines Don't Have DI

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. But 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.

mmarshall

An interesting arguement for the usual cost-controls, but I think it overlooks the fact that, in the next few years, tightening CAFE and emissions laws are going to force automakers to do some things that don't necessarily make "buisness" sense; not just with engines, but with other components as well.

Blackraven

I just read the article and it was a very informative read.

I and I think many of us extremely appreciate hearing about this topic from a technical perspective (and from the point-of-view of a Ford engineer).

bitkahuna

iTrader: (20)

great article.

mmarshall, may not make business sense today, but since they've already built a version with DI, they can bring it back if circumstances require.

The G Man

Dollar per HP, DI engines are not the most cost effective, but Ford could have use that same argument to optimizing breathing on their DI engine and get even better HP and MPG out of it. Honda have been optimizing air flow in their engines for years. I am sure GM could have squeeze a few more HP out of their 3.6 DI engine if they have try to optimizing the breathing.

MR_F1

Wait.... they don't? I could have sworn I read that they did.

The G Man

Mr F1, you are right once again. Ford's new Ecoboost engine use the direct fuel injection technology.

http://media.ford.com/article_displa...ticle_id=29653

caymandive

iTrader: (2)

Just curious, but are there limitations to how much power an engine can produce with direct injection? Seems like the cars with DI aren't as mod friendly as without DI. If there are limitations, what are they exactly?

Blackraven

Well in this case, I guess what Ford did shows that improvements can be made even without resorting to DI.

More like DI as an option and not a requirement.

@anyways
I hope we can also get input from any forumer who has background in science (esp. physics) and/or engineering.

That and I also gotta review my understanding of the concept regarding the law of conservation of mass (especially regarding 'entropy' and heat cycles)

My shallow understanding of it goes on how much energy from the fuel actually makes it to the engine system thus outputting into performance.

I guess all the carmakers are doing is to minimize the losses that leak out through the combustion process (hence the relatively low energy efficiency of internal combustion engines).

Anyways, if there are scientists or engineers in this forum, maybe you can care to enlighten me more on this.



Another *possible* disadvantage of direct injection engines is that you get more performance but will require higher octane fuel. Otherwise, the engine will not function optimally and could break down.

This is most likely the reason why Lexus Manila DOES NOT offer any of their cars with direct-injection here in the Philippines.......due to our ****ty quality fuel.

LexFather

I am impressed with Ford engines with or without DI. They have invested way more in new powertrains and engines than the supposed engine/technology company, "Honda" and also are showing Toyota a thing or two.

lobuxracer

iTrader: (2)

Duratec 3.7 liter 305 hp, Lexus 2GR-FSE 3.5 liter 306 hp.

5.0-liter V-8 412 horsepower, Lexus 2UR-GSE 416 hp.

Both Lexus engines are DI+port injection, and have similar fuel economy. Where's the big deal?

This almost sounds like the carburetor guys talking about how a Weber side draft atomizes fuel better than any EFI system (which is absolutely true at WOT). It still doesn't mean it's a good path to the future.

RXSF

i beleive the new focus will have a 4 cyl engine with direct injection, but no turbo so it is not ecoboost

jadu

iTrader: (42)

I was never a fan of ford until i got my mazda. I've had it for 6 years. Its powerplant is the ford duratec 30 (3L V6). No DI, but I consistently get 24 mpg

bitkahuna

iTrader: (20)

i'd say it's a big deal if regular ford engines have caught up to lexus.

LexBob2

There's not that much difference in similar sized modern mainstream engines these days. Especially in the areas of output, fuel economy, performance etc.