I Bin Therbefor

Although this is pick up specific; I've bolded parts that are more GM general and should apply to the Corvette. I've also deleted a lot of the pick up marketing hype

"Cylinder Switch Off Delivers Advantages to Chevy Silverado
Four cylinders deactivate to save fuel during light-load driving
2012-08-14

General Motors improves the fuel efficiency of its mainstream 5.3-liter V-8 engine by switching off four of the cylinders when they aren’t needed.

“Rather than adding turbochargers or multi-valve cylinder heads to increase the power of smaller engines, we chose to keep the proven capability of our larger V-8 truck engines, and save fuel by switching off half of the cylinders when they aren’t needed,” said Jordan Lee, global chief engineer for small block engines.

A combination of simple hydraulic valves and sophisticated software switch off the cylinders when the driver doesn’t need full power. When more power is needed, the system, called Active Fuel Management, seamlessly reengages the additional cylinders.

“With recent increases in computing power, we can combine sophisticated digital design, powerful control strategies, and simple, robust mechanical systems to bring real benefits with no added cost to our customers,” said Lee. “Think of the difference between a cassette recorder and an iPod MP3 player – more moving parts are not always better.”

By giving customers V-8 power and capability when they need it, with enhanced fuel efficiency when they don’t, Silverado offers the best EPA fuel economy estimates of any V-8 pickup, said Lee. “In fact, our 5.3-liter V-8 delivers EPA fuel economy estimates comparable to some competitors’ V6 engines.”

The mainstream 2013 Silverado 1500 4WD with the available 5.3-liter V-8 has an EPA highway estimate of 21 mpg, matching the estimates for a leading competitor’s 4WD model with a more complex, less-proven boosted V-6.

For customers looking for even better fuel economy, the 2013 Silverado XFE model with the 5.3-liter V-8 has an EPA highway estimate of 22 mpg, retaining all the capability and dependability of other Chevy V-8s.

“For each vehicle program, our task is to choose the best technology for each vehicle and its customers,” said Lee. “For millions of people who depend on their trucks and expect them to last, we believe our V-8 engines with Active Fuel Management are an excellent solution.

“As GM develops future vehicles . . . we will continue to draw on our company’s unsurpassed global powertrain portfolio, which includes direct injection, clean diesels, vehicle electrification, turbocharging, supercharging, and other technologies,” said Lee.

“But as with our current V-8 engines with Active Fuel Management, the starting point is always what’s the right solution for the customer and the way they use the vehicle.”

Apparently this is a response to the GM government appointed leaders' comments about GM's power train technology lacks. More important to the C7 is "For each vehicle program, our task is to choose the best technology for each vehicle and its customers". If we knew what Lee believes is important to the Corvette owner, we'd have a better idea of what the Gen V holds for the Corvette. GM has announced DI and a new combustion process for all Gen Vs. What else for the Corvette?

Dudeurgettnavette

I'd hate to hear the exhaust on that engine when it switches from 8 to 4 cylinders.

MythMaker

True, but combine it with a system like NPP it might not be so bad. Under WOT you would be on all 8 cylinders anyways. And they could make it so under idle it always uses 8 to keep the exhaust sound.

I honestly wouldn't mind if they just made the cylinder de-activation an option. an ECO option if you will. Would be great for long road trips or just cruising down the highway.

I wouldn't even mind the "engine" auto-stop-start feature they have on BMWs if it was optional. Sitting in bad traffic it would be great to not just watch the fuel $$$ disappear.

427-Z06

Go try one of the current trucks, think you will be surprised. I have a Tahoe and an Avalanche with this feature and you cant tell when it switches and its very smooth. Basically its only on 4 cylinders when you are cruising. Start and stop and acelleration its in 8 cyl mode. Works really well, and when you put your foot into the throttle all 8 are always there.

Larry/car

It is the latest and greatest, if it works well and is reliable I am all for it. If you worry about sound, they can install an optional electronic sound generating system. Then all would have the best of both worlds.

Bandit's C4

Ask anyone who remembers the Cadillac version during the '80's... the mighty 4-6-8 configuration.

Didn't last long.

Jinx

They quoted highway mileage, but not city mileage or combined mileage.

If the news was good they wouldn't have omitted it, so it's reasonable to assume that the AFM Silverado doesn't match or beat the city mileage of the EcoBoost F150.

chaase

That didn't last long because they didn't have the technology to make it work correctly. There are lots of cars on the market with cylinder deactivation.

McGirk94LT1

Um... this has been on the 5.3 and certain 6.0's for years now... I confused...

235265283...

I Bin, thanks for finding and posting.

Of course the real question is: Will the Gen V engine version in the C7 have cylinder deactivation?

Many of us have speculated on this in other C7 threads. I would prefer that it doesn't have cylinder deactivation (and pay the price of a slightly lower fuel economy rating), but I give it about a 50/50 at this point.

Three thing for sure, IMHO:

1. CAFE compliance will have a substantial effect on the C7.

2. Most of us would prefer cylinder deactivation to automatic stop-start (not likely for C7, IMHO).

3. If the C7 has either of these features, they will not be options and the will not be easy to "disconnect".

BuckyThreadkiller

I've had Displacement on Demand or Active Fuel Management or what ever they call it on my 2007 Yukon. I've never noticed when the transition happens. If it weren't for the DIC readout saying V4 or V8, I'd never know.

My bigger complaint is that the system on my Yukie doesn't switch to 4 cylinders often enough. It's a V8 idling at stop lights, sitting in traffic, doing 20 mph stoplight to stoplight in town. Totally unnecessary times to have a V8.

Buick actually shuts theirs completely off, the AFM ought to be able to do the same thing on the truck.

It's interesting they are touting this on the 2013s rather than making it a big deal on the new trucks coming for 2014. But I guess they are seeing some hits from Ford's EcoBoost marketing.

As for CAFE compliance. They build fewer than 20,000 Vettes a year. The impact on CAFE is nil compared to the 500,000 pickups GM will build.

RussM05

There is not a single part of the engine or engineer involved in the current program that had anything to do with the Caddy 4-6-8 program so I don't worry about it.

235265283...

If by this statement you mean to imply that GM has no concern about the C7's EPA fuel economy test scores, then I respectfully disagree with you. Is it also your belief that recent manual-transmission Corvettes have skip-shift because GM thinks that most buyers desire that feature?

Without question GM sells way more pickups than Corvettes. But I think GM judges all models on an incremental effect basis, e.g., a model with incrementally negative CAFE impact would need to be justified by a higher than corporate average profit contribution.

96ss#80

I have a 2009 Silverado with a 5.3 i cant tell when it switches at all! and as for power… I just hauled a 2008 Altima from Columbus Oh to Dayton Oh (about 75 miles or so) I estimate the load (trailer and car) to be approximately 4500 lb give or take a hundred or two… I could barely tell it was there as I cruised at 75 mph.

BMWDAD

After owning my twin turbo 6 cylinder BMW for 5 years (no problems), when the time comes I WILL not pass it on to my adult son. I am for simple tech, that will last me a long time for the C7.

CPhelps

I believe CAGS skip shift was more to ensure that the Corvette was not hit with gas guzzler tax, something beneficial to GM and owners alike. Obviously they will strive for the best fuel mileage possible, and everything helps, but I tend to agree that from a CAFE fleet average perspective the C7s volume is so low that it has fairly low impact on GM's fleet total average.

I can't recall off the top of my head if it is the VVT or the AFM on the current Gen IV engines that limit camshaft lift (Part of why L99 in the automatic Camaro SS is rated at ~20 hp less than the LS3 in the manuals), but hopefully the Gen V implementation will not be too difficult to disable if it is necessary for higher lift cams.

Joe_Planet

I had a 2007 tahoe with this feature, what are these guys smoking?????

McGirk94LT1

Ya know, that's a brilliant idea actually. A button to disable 4 cylinders for as long as its selected(Que the ITS A SPORTS CAR THAT SHOULD GET 10MPG crowd). Yeah it would result in less then spectacular acceleration, but if you have control over it, you'd know that from the start. I get that idea from you and from the old zr-1 with its normal/full power key. It would be pricey today considering it ran on 16 injectors, but if you're simply disabling 4 out of 8 injectors indefinitely, then that's no extra cost right there. On a multi state cruise doing 70 for 2 hours straight its gotta make the mpg sky rocket. If all I'm doing is going from toll booth to toll booth, might as well keep 4 of em off right?

jackhall99

Why are you bashing at what BuckyThreadkiller posted about low volume Corvette production having minimal impact on CAFE? He's right and you are fairly brassy to twist his words.

I've posted to you and others on the Corvette's almost non-existent impact on GM's CAFE results, but some don't grasp that fact.

jackhall99

You get it; some still don't.