For Release: Oct. 28, 2003, 8 a.m. ET
GM INTRODUCES GEN IV SMALL-BLOCK V-8 FOR TRUCKS

NEW VORTEC 5300 FEATURES FUEL-SAVING DISPLACEMENT ON DEMAND TECHNOLOGY FOR ’05 TRAILBLAZER EXT, ENVOY XL AND ENVOY XUV
PONTIAC, Mich. – GM is writing a new chapter in the history of the small-block V-8 with the Gen IV engine, which, when equipped with its innovative Displacement on Demand (DOD) technology in trucks, has the capability to operate more efficiently on fewer cylinders.

DOD technology enables fuel economy gains of 6 percent to 8 percent in certain light-load driving conditions by reducing the number of cylinders engaged in the combustion process. The Vortec 5300 small-block with DOD debuts on V-8-equipped versions of the 2005 Chevrolet TrailBlazer EXT, GMC Envoy XL and Envoy XUV. A version of the Vortec 5300 V-8 without DOD is available in the 2005 Buick Rainier.

An automotive application of the Gen IV small-block without DOD also debuts later in the 2005 Corvette.

“The versatility, strength and performance of the legendary small-block V-8 continue to grow,” said Sam Winegarden, chief engineer of small-block engines. “In trucks we’ve maintained the broad, usable torque customers depend on for countless tasks, while in the Corvette, we’ve upped the ante with the largest, most powerful small-block ever offered as standard equipment. You’ll have to wait until the 2004 North American International Auto Show to get the details, but believe me, it’s worth the wait.”

Virtually imperceptible
The Vortec 5300 all-aluminum truck engine with DOD is rated at an estimated 290 horsepower and 325 lb.-ft. of torque in V-8 mode, and supports tow capacities comparable to the previous 5.3-liter small-block. A sophisticated, next-generation engine controller determines when to deactivate cylinders, allowing the engine to maintain vehicle speed in lighter-load conditions such as highway cruising. The process is seamless and virtually imperceptible.

When the cylinders are deactivated the engine effectively operates as a V-4, with alternate cylinders on each cylinder bank disabled. The engine returns to V-8 mode the instant the controller determines the vehicle speed or load requires additional power.

“Displacement on Demand is a win-win for drivers who rely on the power of the small-block V-8 and are conscious about fuel economy,” said Chris Meagher, assistant chief engineer of small-blocks for trucks. “The implications of this technology are tremendous.”

Factors including oil temperature, rpm, coolant temperature and throttle position help determine the operating mode of the engine. The engine controller automatically shifts between operating modes as these factors and driving conditions dictate.

“From behind the wheel, there’s no indication or sensation that the operating mode of the engine has changed,” said Meagher. “DOD operates only in conditions when the load on the engine doesn’t require all eight cylinders – the torque to climb a hill, to pass or tow is never compromised.”

Two-stage lifters
The key to DOD’s efficiency and virtually imperceptible operation is a set of special two-stage hydraulic valve lifters, which allows 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.

Solenoids in the engine lifter valley 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 vibration and acoustic dynamics of the V-8 and V-4 modes are different, engineers tuned the exhaust system of DOD-equipped vehicles to compensate for the changes. A pressure-activated valve in the muffler automatically switches when the engine mode changes, adjusting the exhaust path to deliver the appropriate noise reduction. Additionally, tuned exhaust and engine mounts were designed for the multiphase engine operation.

The engine’s electronic throttle control (ETC) also is used to increase manifold pressure in V-4 mode so that the engine can maintain a V-8 torque load.

Gen IV features
Based on the architecture of the Gen III small-block introduced in GM trucks in 1999, the Gen IV engine incorporates several significant design changes:

New casting for iron and aluminum blocks with redesigned oil galleries to support DOD oiling requirements
Knock sensor locations moved out of lifter valley to provide room for DOD lifter oiling solenoids
Camshaft sensor relocated from the rear of the block to the front of the block provides room for new oil galleries
Higher capacity oil pump accommodates increased oil circulation requirements of DOD
Coil-near-plug ignition has larger, more efficient coils that require less energy to produce a comparable spark
Returnless fuel system for improved evaporative emissions
Larger throttle body angled upward for improved water drainage
Electronic throttle control (ETC) on all models for improved throttle response and DOD signaling
Next-generation engine controller operates DOD, ETC and other engine functions
Separate controller for transmission
Additionally, the Vortec 5300 benefits from continual improvements incorporated into later versions of the Gen III engine, including iridium-tip long-life spark plugs; pistons with floating wrist pins; a redesigned water pump that significantly reduces the probability of a leak; and a stronger, long-life timing chain. It also is compatible with E-85 fuel.

Gen IV engines share the deep skirt engine block design of previous GM truck engines. Extending below the crankshaft centerline, the rigid block contributes to world-class smoothness and strength. It also allows cross-bolted main bearing caps for additional strength and dimensional accuracy.

The engines’ similarities also include the balanced cylinder head design, which promotes optimal performance and efficiency with identical airflow and energy direction to each cylinder. A tall intake manifold plenum helps draw a longer, tuned path for incoming air to build low-rpm torque, allowing the engine to make torque at low rpm and sustain it over a broad rpm band.

“The Gen IV’s new features and proven architecture ensure the vitality of the small-block V-8 into the foreseeable future,” said Meagher.

More than 2 million DOD-equipped vehicles will be on the road by 2008.

GM Powertrain is a global producer of engines, transmissions, castings and components for GM vehicles and other automotive, marine, and industrial OEMs. Headquartered in Pontiac, GM Powertrain has operating and coordinating responsibility for General Motors powertrain manufacturing plants and engineering centers in North America, South America, Europe, and the Asia-Pacific region.

 

The Gen III silverado 5.3L puts out 295HP, that is disappointing to see that the Gen IV puts out less HP than the same size Gen III V8

 

First off, it's 5 freakin' HP.
2nd, the 5.3 in the 2004 Rainier, Envoy XUV, and trailblazer EXT are all rated @ 290hp. . . and those are the vehicles mentioned in the article.

The 5.3 in the trucks is rated at 295. . .

Fact is, have those 2 different engines in the same exact vehicle and the difference would depend on which one is the better built from the factory , or "Factory freak".

 

i think its still disappointing there's no power boost whatsoever. of course there's enough stuff in the GEN 4 to still be happy about and i suspect the power rating will go up in another year or two if the current trend is to continue. I mean its not like the 5.3 is underpowered or really lacking as it is. GM just probably didn't want to show all its cards at once. that's all...

 

THe jump from the Gen II 5.7L to the Gen III 5.7L went from 300HP to 350HP. I was hoping the Gen IV V8s would at least get a 10% boost. I guess we will have to wait for the 3 valve heads.

 

The 1996 LT4 (Gen II) was rated at 330 HP; the 1997 LS1 (Gen III) was rated at 345 HP. So the jump was only 15 HP.

I agree that GM is probably just leaving a bit of room for future improvement. And peak HP values say nothing about the power generated throughout the rpm range.

 

I'd say that the LT1 is the gen II equivalent of the LS1 and LT4 the equivalent of the LS6.

Also the 5.7L silverado Gen II put out 255HP, The original Gen III 5.3L put out 275HP. 20HP more and 400cc less displacement.

I was hoping the Gen IV 5.3L would out perform the new 3v 5.4L Ford. Hopefully the 3v 5.3L Chevy V8 won't be too far down the road.

 

I wouldn't worry about that. The Ford weighs a ton more and the smallblock still has a better throttle responce.

 

Forget Ford---I don't think much of their new 3 valve 5.4L--- (plus the truck is 500lbs heavier) Nissans the one to worry about.

Despite their modest claims of power the Titan runs to 60mph in the very low 7 second range.

Gm should put the 6.0L in the half-tons.

No variable valve timing yet for the Gen IV?

 

Nissan has set the new benchmark for mainstream power and torque. Toyota is pulling dead last in this arena and Fords are hampered by way too much weight. At least Dodge seems to be trying with the Hemi. However, GM should be embarassed to have let their market leadership slip away.

If GM was really concerned about fuel economy, they should have made steps that would have impacted economy and performance as well. How about using Isuzu's world class direct injection technology? What happened to variable valve timing? Variable valve timing should have been part of any cylinder deactivation system. It's not only possible with a pushrod motor, but fairly cheap to do - far cheaper than in a DOHC motor.

 

For the love of Pete, why are we wringing our hands about this?

When has GM failed the truck market in power? I agree that the 6.0 whould be available in ALL half-tons (it IS available in the SD half-tons), but golly gee, they're doing just fine.

Ford is in a world of hurt if their truck doesn't set the world on fire, and Nissan WILL NOT be serious competition - especially in the heavier trucks.

Direct injection is coming, but there has to be the benefit to justify it financially, and that benefit is just starting to crystallize.

In the end, GM is yet again taking a lighter and simpler engine design and pounding the snot out of everyone in the game with it. Remember, GM underrates EVERYTHING, by a LOT. Unlike some of the competition....

 

Considering that GM now has the oldest range of fullsized trucks in the industry, they sure have some reason to worry. Maybe they picked the wrong time to start resting on their light truck laurels. Take a look at a Chevy or GMC lot, and the products look about as hip as a buzz cut.

Now, take a look at Nissan. The Pathfinder Armada is a real blast - and yes, I drove one - and the Titan looks equally aggressive. These vehicles won't have the volume to soak up all those old-school domestic buyers, but they will take the cream off the top. Crystal ball: more rebates for GM trucks.

GM had better start uprating their powerplants, and freshening their truckline right now. No more goofy restylings like 2003. All of the fuel economy ain't gonna cut it.

 

When is the completely new Silverado due, 2005? The F-150 never had problems maintaining sales the last couple of years even with soft styling and even softer powertrains. At the end of the day, people will still be buying GM trucks by the boatload...just long enough for GM to trump the F-150 (and everyone else) again.

 

Hey I might want to steal this part and reverse it for my Camaro.... Muffled at normal driving, but WOT over 3000 rpm, flips it to straight out..

6 to 8% fuel economy -s ounds good, but 6 to 8% of 15 is 1 mpg..

I wish the new GM trucks will be something like that concept silverado I saw in the magazine.. with an IRS in back. which allowed the floor bed to be alot lower (vs Ford's trick of raising the walls for more space ) If they design them right (tires stay nice and square thruout suspension travel), and make em strong enough, would there be any drawbacks in towing and offroading (besides cost?)

 

The outgoing F-150 sold so well because the pricing was well below GM's. Ford Credit also "bought deeper" than GMAC. Overall, the strategy worked pretty well. It would have worked better if they'd given the F-150 a restyled front clip a couple years ago. That strategy worked with the old, old F-150 - three restyles over the years.

For better or worse, GM had better worry about Nissan just as much as Ford. Both companies are chasing the niche that Silverados and Sierras have carved out. It isn't just about the blue oval vs. the gold bow-tie anymore.