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GM Powertrain Unveils More Engines with Direct-Injection, Active Fuel Management and E85

GM Powertrain today introduced three new versions of existing engine models: a 3.6-liter V-6 gasoline engine with direct injection and variable valve timing (VVT); its first V-6 application of Active Fuel Management (cylinder deactivation) on the 3.9-liter V-6 for 2007 Chevy Impala; and E85 ethanol fuel capability on the 3.9-liter V-6 offered in 2007 Chevy Uplander fleet models.

The 3.6L VVT DI engine reduces fuel consumption by up to 3% while increasing power by 15%. The 3.9-liter AFM application improves fuel economy by an estimated 5.5% (from 22 mpg EPA combined to a projected 23.2 mpg combined).

This brings the total of new or significantly revised engines for model year 2007 to 19.

The 3.6-liter VVT DI. GM will apply a version of its 3.6-liter V-6 gasoline engine with direct injection and variable valve timing (VVT) technologies in the 2008 model year. The company will announce a specific vehicle target later this year.

The application of direct injection technology to the 3.6-liter VVT engine contributes greatly to a 15% increase in horsepower over the current levels that range from 240 hp to 267 hp; an 8% increase in torque, and up to a 3% improvement in brake-specific fuel consumption (BSFC). An approximate 25% reduction in cold-start hydrocarbon emissions is also achieved.

GM projects that by 2010 one out of every six GM vehicles in North America will be equipped with a direct injection engine.

Direct injection delivers precisely metered fuel directly to the combustion chamber, producing a cooling effect in the chamber. Cooling the incoming air charge enables a higher compression ratio (greater than 11.0:1 in the case of the 3.6), which also improves engine efficiency. Less fuel is required to produce the equivalent horsepower of a conventional port injection combustion system.

The 3.6-liter VVT with direct injection will be our highest specific output non-turbocharged V-6 engine, as well as one of the most fuel-efficient offerings in our high-feature family.

—Tim Cyrus, chief engineer for high feature V-6 and Northstar V-8 engines

The 3.6-liter is GM’s third engine with gasoline direct injection. The announcement of the 3.6L VVT V-6 with direct injection comes after the introduction of GM Powertrain’s Ecotec 2.0-liter four-cylinder Turbo engine with direct injection on the 2007 Saturn Sky Red Line and Pontiac Solstice GXP roadsters. GM has been delivering a naturally-aspirated Ecotec 2.2-liter direct injection engine on Opel models in Europe since 2004.

The fuel injectors in the gasoline direct injection system are located beneath the intake ports. The intake ports only transfer air, unlike port fuel injection, which flows air and fuel, thus increasing efficiency.

Direct injection requires higher fuel pressure than conventional fuel injected engines and an engine-driven high-pressure fuel pump is used to supply up to 1,740 psi (120 bar) of pressure.

The system regulates lower fuel pressure at idle—approximately 508 psi (35 bar) and higher pressure at wide-open throttle. The exhaust cam-driven high-pressure pump works in conjunction with a conventional fuel tank-mounted supply pump.

The 3.6-liter VVT DI is based on GM Powertrain’s 60-degree dual-overhead cam (DOHC) V-6 engine. The 3.6-liter V-6 VVT DI employs four-cam phasing to change the timing of valve operation as operating conditions such as rpm and engine load vary.

The result is linear delivery of torque, with near-peak levels over a broad rpm range, and high specific output (maximum horsepower per liter of displacement) without sacrificing overall engine response and driveability.

Cam phasing also reduces exhaust emissions by optimizing exhaust valve overlap and eliminating the need for a separate exhaust gas recirculation (EGR) system.

By closing the exhaust valves late at appropriate times, the cam phasers allow the engine to draw the desired amount of exhaust gas back into the combustion chamber, reducing unburned hydrocarbon emissions.

The return of exhaust gases also decreases peak temperatures, which contributes to the reduction of oxides of nitrogen (NOx) emissions. In tandem with the 25% reduction in cold-start hydrocarbon emissions brought on by direct injection, the 3.6-liter VVT DI V-6 surpasses all emissions mandates, and does so without complex, weight-increasing emissions control systems such as EGR and air injection reaction (AIR).

3.9-liter Active Fuel Management. The new 3.9-liter engine with AFM is GM’s first V-6 application of its cylinder deactivation technology. (GM had pushed back the introduction of the V-6 AFM engine back to the 2007 model year to do additional fine-tuning on noise and vibration.) (Earlier post.)

Preliminary testing of the 2007 Chevy Impala equipped with the 3.9-liter V-6 with AFM indicates an estimated 20 mpg in the city and 29 mpg on the highway—improvements of approximately 5.5% and 7.5%, respectively.

Active Fuel Management enables the engine to automatically operate on half of the engine’s cylinders under light load conditions, improving efficiency by reducing fuel consumption when the cylinders are deactivated.

GM offers this technology in 11 vehicles for 2007, including trucks and SUVs – more than any other automaker. The Impala is GM’s first V-6 application of AFM in North America. GM also is launching a 3.0L V-6 with AFM in China that will debut in the Buick LaCrosse this summer.

A new engine controller determines when to deactivate cylinders, allowing the engine to maintain vehicle speed in lighter-load conditions such as highway cruising. When the cylinders are deactivated, the engine effectively operates as an inline three-cylinder engine, with cylinders 1, 3 and 5 deactivated on the left cylinder bank. The engine returns to V-6 mode the instant the controller determines the vehicle speed or load requires additional power.

The special hydraulically-activated de-ac lifters that enable GM’s Displacement on Demand.

GM uses two-stage hydraulic valve lifters which allow the lifters of deactivated cylinders to operate without actuating the valves. The lifters have inner and outer bodies, which normally operate as a single unit. When the engine controller determines cylinder deactivation conditions are optimal, the outer body moves independently of the inner body on the disabled cylinders’ lifters.

The outer body moves in conjunction with camshaft actuation, but the inner body does not move, holding the pushrod in place. This prevents the pushrod from actuating the valve, thereby halting the combustion process. Also, fuel supply to the fuel injectors is halted while the cylinders are deactivated.

Solenoids in the Lifter Oil Manifold Assembly (LOMA) operate to deliver high-pressure oil to the switching lifters, activating a release pin to separate the inner and outer bodies. Oil circulation and pressure do not vary regardless of the engine’s operational mode. Lifter design and pushrod length are the same for every cylinder, but camshaft lobe profiles differ for cylinders designated to be deactivated.

Because the noise and vibration characteristics are different between a V-6 and the effective inline three-cylinder operation when the 3.9L is in fuel-saving mode, engineers tuned the engine and exhaust system to maintain consistent operational sound and feel. For example, the alternator features a unique decoupling clutch that instantly adjusts tension on the accessory drive belt when the engine switches from six- to three-cylinder operation.

The 3.9-liter’s cam-in-block variable valve timing technology also works synergistically with Active Fuel Management, as the cam phaser enables the engine to produce maximum torque during three-cylinder operation. This allows the engine to remains in fuel-saving mode longer.

The VVT system incorporates a vane-type camshaft phaser that changes the angular orientation of the camshaft, thereby adjusting the timing of the intake and exhaust valves to optimize performance and economy, and help lower emissions. It offers infinitely variable valve timing in relation to the crankshaft.

The cam phasing creates “dual equal” valve timing adjustments. In other words, the intake valves and exhaust valves are varied at the same time and at the same rate. The cam phaser vane is attached to the camshaft on the front journal—a technique made easier by the assembled-camshaft design developed by General Motors.

With this design, separate camshaft lobes are installed on a hollow camshaft tube rather than the traditional method of grinding a camshaft from a single piece of stock.

Hydraulic roller lifters with low-friction followers complement the camshaft, and the engine controller enables the engine’s cam phasing. The system’s demand for precise camshaft position information is met with a unique, cam target ring with four equally spaced segments that communicate the camshaft’s position quickly and accurately. Also, a leaf spring-type tensioner is used on the timing chain to ensure precise tension.

The 3.9L V-6’s camshaft is unique and matched to the engine’s bore-and-stroke characteristics. It is different, for example, than the camshaft in the 3.5L V-6.


Michael G. Richard

"The 3.6L VVT DI engine reduces fuel consumption by up to 3% while increasing power by 15%."

That's the problem right there. Instead of putting efficiency gains into downsizing and fuel economy, they put them into yet more useless power.

The Anonymous Poster

Compared to Honda and Toyota, GM's V6's were underpowered. They are just now getting on the same level.

Michael G. Richard

I'm not saying that it's not a problem with other car makers.. The horsepower race is a problem all over.

But at least Toyota and Honda sell decent small cars and hybrids... GM should definitely bring some of its Opel cars over to North-America.

Sid Hoffman

The good news is that they got on board with DI at all. Honda doesn't sell even one single direct injection car in North America and hasn't even announced a timeline to ever introduce such technology. Even in Japan the Honda Stream minivan is the only vehicle they have with DI.

Like I said, the good news is they got on board with DI. It's a lot easier to just grind a shorter throw crankshaft than develop a DI system from scratch. I'll bet you it would take no more than 3 weeks of development time to put out a 3.0 liter engine based on their 3.6 liter which would then still produce plenty of power while delivering much improved fuel economy.


Maybe GM's customers want more power?

Michael G. Richard

"Maybe GM's customers want more power?"

People want lots of things that GM isn't giving them... Which could explain how well they're doing these days.

fyi CO2

GM customers who want more power, stand up and be counted!
OK, done. This article echoes GM's epitaph, they're grasping at straws.

Joe Rocker

They won't care about power when gas goes to $5 a gallon.

Mark A

I knew someone would bash GM.

GM should be commended for introducing small incremential improvements, such as this and cylinder deactivation. Other carmakers are going for home runs, while GM is getting base hits and walks, to use a baseball analogy.

GM actually has quite a few fuel efficient models and engines out, which should put a damper on recent GM bashings. Dont complain about GM's lineup, because they are delivering what "Joe consumer" wants (or wanted). Chrysler should be the group receiving the most criticism, especially in this so called inappropriate horsepower race. They introduce a new vehicle, and, as long as there is a "Hemi" reference in there somewhere, they get a free pass. They could be in for hard times soon. Chevrolet's Corvette offer stunning performance, but if driven sensibly, delivers up to 28-29 mpg. Now thats performance, in an age when performance figures should start including mpg numbers and maximum miles per tankful.

Michael G. Richard

This is a post about GM, so of course the comments (positive or negative) are going to be about GM.

There are very few posts about Chrysler here (probably because they don't do much that fits on GCC), but if there was, I'm sure you'd see the same kind of thing.

I'm glad GM is improving things, but it's not much of an improvement - as I said - if almost all the efficiency gains are going to power and not fuel economy. I mean, would we be better off if all cars had 50% more power or 50% better fuel economy? We already have "boring" cars that have more horsepower than the Trans Ams and other sports cars of not so long ago...

fyi CO2

To follow up with another baseball analogy, the only way GM can get on base is when they don't move and are hit by the pitch (the Corvette excluded).

"delivering what "Joe consumer" wants (or wanted)"
definitely what "Joe consumer" wanted (past tense).

Joseph Willemssen

Chevrolet's Corvette offer stunning performance, but if driven sensibly, delivers up to 28-29 mpg

OK, I like the Vette and its performance is impressive, but NO ONE buys that vehicle to "drive sensibly". The numbers you're giving are for someone loafing on the highway under perfect conditions - if they're lucky. Real-world MPG for that car is below 20 MPG on average, probably well below.

Chrysler should be the group receiving the most criticism, especially in this so called inappropriate horsepower race.

Strange you would say that, since the 300C with AWD has the same fuel economy rating as the Vette. It's because they're using DoD tech on that engine. But again, in the real world, people are not going to be driving these cars "sensibly".

fyi CO2

How can I get one of those (free) E85 yellow Tshirts?


This is a step in the right direction, but yet again, GM is still doing it the "old way". By that I mean that they must not be using the latest DI technology. If they were, the fuel efficiency gains would be closer to 10% without downsizing. That is primarily accomplished through running a lean mixture. I know that presents new emissions issues, so maybe GM can't figure that out. Yet again, must be using the technology of 5 years ago!

GM actually has quite a few fuel efficient models and engines out, which should put a damper on recent GM bashings.

Name one GM car that gets over 40mpg. Just one. (Hint: There aren't any.)

GM is trying like mad to make their cash cows, body-on-frame SUVs, get "best in class" fuel economy. But when gas gets over $4/gallon, they're going to find out that consumers don't want to choose between 12mpg and 20mpg. They want to choose between 30mpg and 40mpg.

If GM was serious about fuel economy, they'd find a way for their only subcompact, the Aveo, to get more than 34mpg. If they were really serious about fuel economy, they'd push for increased CAFE standards that include SUVs. They'd throw their hat over the wall.

Mark A

Can someone verify whether a 50% (or 3% or whatever)increase in power could somhow directly correlate into a 50% (or 3%)increase in better fuel economy? I have searched, but could find no reference to that. They do report a 3% or 5.5% decrease in fuel consumption.

Its also interesting that this direct injection technolgy achieves a 25% reduction in cold start hydrocarbon emissions. Taylor made for a hybrid. Does the Prius gas engine have direct injection?


"I knew someone would bash GM"
Someone! One? Where have you been living....let me guess, Detroit.


GM deserves all the bashing it gets.

Not much sense having fuel injection without a supercharger. Then it takes an engine redesign.

I'm not holding my breath.

Sid Hoffman

The Prius is not direct injection, nor is the Civic Hybrid. The only DI Toyota has implemented that I know of are in the Lexus engines. Again, Toyota only pretends to be environmentally friendly. They implemented DI in the Lexus IS350 so they could keep up with the Infiniti G35 in the horsepower war.

Sid Hoffman

Lucas, we're talking about DIRECT injection, not fuel injection, of which there are three kinds:

Throttlebody Fuel Injection
Port Fuel Injection
Direct Injection

None of which have anything to do with turbo or supercharging, but thanks for letting us know how ignorant you are so we can ignore the rest of your comments.

Bob Tasa

Would be nice if GM woke up but that very sadly wont happen. When they cut staff they did so at the wrong end. They need all the labor they can get to change. What they dont need is OLD ideas from OLD salemen managers that should have been fired a couple of years ago. Bob Lutz said at the Auto Show Hybrids are loosers. In Feb or Jan of this year he said I think SUV's will stil be big winners for GM. Gas was already at 2.60 gal and climbing.
That is the insane things going on at GM.
If Iran keeps up with the threats we are going to see 5.00 gallon gas or MORE.

gerald earl

Anyone see the stackable commuter car being developed by MIT? Apparently it was financed by GM.

IBM was a dinosaur that reinvented itself and now is performing quite well.Any possibillity that Gm has gotten the message and is in the process of turning around a bloated hidebound corporation that can answer to twenty first century challenges?

Nah,Gm raped mother earth and is now killing her children.

Mark A

"This is a post about GM...............There are very few posts about Chrysler here (probably because they dont do much that fits on GCC), but if there was, I'm sure you'd see the same kind of thing..............

That should be a very telling statement, that GM has many articles on this website, with this website being GCC, or GREEN---CAR---CONGRESS Maybe they are closer to being green than they are yellow?

Also on the Vette "....Real-world MPG for that car is below 20MPG on average, probably well below....."
Is this what you get on YOUR 2006 Vette? According to, the Vette delivers up to 28 MPG highway. Several auto magazine articles I have read recently have also reported 27-30+ MPG, amazing themselves. But I disagree that people who buy Vettes do not drive sensibly.

Lou Grinzo

One bright spot for GM is that a recent addition to their board is Jerry York, the guy who played a major role in turning IBM around. I used to work at IBM, so I can tell you how wrenching the cultural change was. GM needs at least as large a personality transplant, and so far I see no evidence of it happening. It could simply be too early in the process for the change to be publically visible, but I'm doubtful that explains it.

GM has painted itself into a very tight and nasty corner. The only way it will save itself from a horrible trip through the bankruptcy process is to give up this bizarre notion that it can build the kinds of vehicles it likes and is reasonably good at (big SUV's) and survive in an era of rising and volatile gasoline prices. They have to get serious about going head-to-head in the US market with the Civic, Fit, Corolla, Yaris, xA, xB tC, and Versa. That market segment is the new battleground, and until they can compete there they'll be consigned to a niche provider of light trucks and some mid- and full-size cars.

Joseph Willemssen

Is this what you get on YOUR 2006 Vette? According to, the Vette delivers up to 28 MPG highway.

Operative words "up to" and "highway". Its combined rating is between 20 and 21, and as I said, people don't buy cars like that to drive "sensibly". I know this from personal experience. Back in the day I had a Z28, which could do reasonably well for fuel economy on long road trips back from school. However, I rarely drove the vehicle that way.

Several auto magazine articles I have read recently have also reported 27-30+ MPG, amazing themselves.

It amazes them that putting a car on cruise control at legal speeds would get near the EPA rating? Maybe they should try doing that with all the cars they test and see what happens.

But I disagree that people who buy Vettes do not drive sensibly.

You don't buy a car that has 500 horsepower, can go 190 mph, and 0-60 in under 4 seconds just to drive 55 in the right lane.

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