How VVT Helped GM Get Best-In-Class MPG In Light-Duty Pickups

How VVT Helped GM Get Best-In-Class MPG In Light-Duty Pickups

When it comes to eight-cylinder gas engines, GM has some twisted engineers who are hard at work in its labs. No, they're not crazy, unless you consider the almost fanatical obsession they have with improving the fuel economy and performance of GM's workhorse motors — two seemingly conflicting goals that are the automotive equivalent of having your cake and eating it, too.

In that case, yep, they're twisted because one of the biggest underhood improvements for 2010 is the availability of variable valve timing across the entire V-8 engine lineup in GM's full-size pickup trucks, that's helped GM grab the title for best-in-class fuel economy.

When it comes to VVT, it's all about the twist. Here's why.

VVT isn't new technology. It's been common in cars since the 1990s. Until then, engineers walked a fine line trying to balance an engine's personality between high performance and daily drivability because one of the most important powertrain components that determined whether an engine would be a pussycat or a tiger was its camshaft.

A camshaft manages the timing of the opening and closing of the intake and exhaust ports in a cylinder. It determines how well an engine breathes and makes power. It's driven by an engine's crankshaft, via a timing belt or chain.

6.2-liter V-8 Engine Cutaway Diagram

Before VVT, camshafts were locked in a single position. The opening and closing of an engine's valves was predetermined by the cam's profile, its lobe lift (measured in thousandths of an inch) and the duration its intake and exhaust valves remained opened and closed. An engine's behavior was fixed from the moment it rolled off the assembly line.

VVT technology changed engine behavior forever by enabling the camshaft to be rotated slightly based on driving conditions instead of being lock-synched to the rotation of the engine's crankshaft. Using a component called a cam phaser, an engine could adapt on the fly to offer a dynamic mix of power as needed or refinement in low-speed situations. Twisting the camshaft forward (advancing) or backward (retarding) was all it took to change that behavior by changing the opening and closing duration of the valves.

VVT brought other benefits, too, including improved emissions due to better control of airflow through the cylinder and combustion temperatures.

Getting VVT into trucks took a bit longer than cars because of the widely varying applications that trucks are used for, from towing to hauling to running errands. Ford was the first to implement VVT in a full-size pickup, when it was introduced in the Ford F-150's three-valve 5.4-liter overhead cam V-8 in 2004. The first GM full-size truck to receive VVT was the 2007 GMC Sierra Denali with the 6.2-liter overhead valve V-8.

VVT Camshaft with Cam Phaser

VVT is a technology that ties many recent advances together to achieve improved power and refinement as well as fuel economy, says Jordan Lee, assistant chief engineer for Chevy and GMC V-8 truck engines.

"Variable timing gives us a lot of flexibility," Lee said. "With fixed cam timing, you're always trying to balance low-speed torque with high-speed power, and then fuel economy and idle stability have to balance in accordance with where the cam timing is fixed. With variable cam timing, we're able to optimize the cam timing for low speeds, and in our truck applications it improves idle stability.

“Alone, it also improves fuel economy by about 2 percent, but at higher speeds and peak torque, we couple VVT with Active Fuel Management [which shuts off half the engines during stead-state driving conditions to save fuel]. It's synergistic. It allows us to run in four-cylinder mode longer and achieve a 5 percent improvement in fuel economy in the 5.3-liter V-8 for 2010 over the 2009 5.3-liter V-8."

In practical terms, the 5.3-liter V-8 has seen its EPA mileage ratings improve from 15/21 mpg city/highway in 2009 to 15/22 mpg in 2010, in the XFE model. That's given GM some new ammo to use against its competitors for bragging rights in the ultra-competitive half-ton truck segment.

"We used to really sweat over horsepower," Lee said. "Horsepower was king for a long time, and a lot of energy went into improving horsepower and torque. Now, fuel economy is the new horsepower war. A tremendous amount of engineering effort by GM is going after fuel economy. It's much more difficult than going after power."

Cam Phaser Assembly

GM's entry-level small block 2010 4.8-liter V-8 with VVT keeps the same gas mileage ratings as 2009's. The Chevy Silverado and GMC Sierra Heavy Duty three-quarter-ton and one-ton pickup trucks also use VVT in the 6.0-liter gas V-8, according to GM powertrain spokesman Tom Read, but trucks in that segment aren't required to rate their fuel economy.

GM is also trying to eke out engine-specific fuel economy improvements beyond VVT by using lower friction elements in the valvetrain, optimizing bearing sizes so they're not bigger than they have to be and using new lubricants and thinner weight oils. "The biggest gains that we're looking at achieving will be by optimizing our combustion system and reducing friction," said Yoon Lee, design system engineer for GM small block truck engines. "Friction is the biggest enemy of fuel economy."

Jordan Lee and Yoon Lee are also using supercomputers to model airflow within the cylinder, following the combustion process molecule by molecule in the fuel/air charge to get the maximum benefit without compromising the engine's idle stability or combustion performance.

"We want the world's smoothest engines as well as crowd-pleasing fuel economy," Jordan Lee said. "That's where a lot of the optimization work is focused right now."

GM’s engineers are intently studying other engine technologies that are just around the corner for use in truck engines, too.

"I think direct injection is one of the most exciting new technologies," Jordan Lee said. "We're getting into it in a big way. It's not on the small block V-8s (yet), but it's technology that we'd consider for the future. It has lots of advantages. Using direct injection, we're injecting fuel directly into the cylinder instead of through a port. It helps cool the charge, so we can run at a higher compression ratio without having to worry about spark detonation. Anytime you raise the compression ratio of an engine, that's the one parameter that gives you an improvement in fuel economy and in power. It's a great technology that goes hand-in-hand with VVT and Active Fuel Management."

Comments

"There are many people out there who are concerned about fuel economy. It is something I am looking at. It isn't my number one priority. It is something one needs to look at when it comes to operational costs. I can't see the need for more horsepower/torque than what is becoming available. Ford's Ecoboost 3.5L is an example of HP with fuel economy. GMC is doing a good job of combining decent power with good fuel economy."


@ Lou's comment- completely agree with Lou. Fuel Economy is the new horsepower war. If it wasn't we wouldn't have car makers mas producing hybrid vehicles. I don't care what you guys say, GM is doing a good job.

I agree with Beth, a one MPG improvement may not sound like much but on a 15 MPG truck thats huge, especially if your doing a lot of driving. I do think the numbers that these companies throw out are a bit decieveing. Dodge, GM, and Ford have comercials out saying they get 20-22 MPG, sure in prestine conditions at a slow set speed on the highway with 2wd only, truth is these trucks average closer to 13-14 MPG.

I wonder what kind of mileage these trucks would get if they cut back on 50hp or so? There is no need for 300-400hp engines.Everyone lived with 140hp back in the 1970s....how did anything get done at that low level?????????
The 1970s GM 350/400,Ford 351/400 and Chrysler 318/360 were paper tigers (unless it was the cop version 360),yet those vehicles still towed,plowed and carried without any major tragedy.Why are people so power hungry?

MPG will be the next brand "battlefield". You can not get much more HP/Torque out of these engines without decreasing long term engine and driveline reliability. Fuel economy would decrease as well. If a guy needs more than 400 hp/400lb/ft (gas) or 300hp/600 lb/ft (diesel) they are "racer boys" or fooling themselves. Ever notice that commercial engines have way less HP than pleasure vehicles? Fuel prices will rise again. I want a truck I can afford to drive. Hybrid pickups are out of the question. A return on investment is 10 - 14 years depending on the price of fuel. Batteries have a 10 yr. warranty but cost $6,000 dollars US (please correct me if I'm wrong!). The Chev hybrid with 6L can only pull 5,900 lb. My GM van with a 4.3 V6 can pull 5,000lb. The price premium for a hybrid puts it into diesel pickup range.
The challenge with diesels is to regain the fuel economy lost with the current emission systems. It doesn't make sense to me to reduce greenhouse gases by decreasing fuel economy from 30 - 60%.
I can see pickups being made with lighter materials to save weight. Aerodynamics are another area to look at. I doubt much can be done in that area because most truck guys like the big, beefy, rig look.

Who cares about a 2wd "truck" anyway that supposedly "saves fuel" , they are useless at best. A real truck has 4x4. A REAL TRUCK war should be based off of the facts if it's dependable, and gets what YOU want to be done. Saving 1mpg here and there shouldn't matter, you'll blow away your saved fuel in a heated drag race against your buddy in his Ford/Chevy/Dodge anyway . And if you are buying a truck, you shouldn't be worried about paying for fuel. Just drive it. IF you can't afford it, well thats just too bad, you shouldn't be getting one in the first place. These SFE trucks are a hoax, more like grocery getters, and destined for the highway.

Bill,

First off,how do you know the Dodge is racing you,people do this to me all the time,they floor it and I dont and they are like you ,and think I was racing. Also I owned a 2002 Dodge with a 4.7 and people like you assumed I had a Hemi,so in other words if I raced them and they won or we were side by side they thought they are tougher than a Hemi,but it wasnt a Hemi..Also if you race light to light ,you dont know what gears the other truck has ,3.23,3.55,3.92 ..

A 390 hp Hemi out runs a 5.4 F-150 ,as proven in performance tests..And some anecdotal evidence, I own a 2010 Dodge 390 hp and my brother in law has a 2010 F-150 and I smoke him light to light ,passing power,and on the highway.We are equal as we can get gear ratio's cab configuration ect..And the hemi out runs a Ford 5.4 !!

Also a Dodge Ram SRT-10 will crap over any Ford F -150..add a supercharger on a SRT and 700+ H.P !! Beats a Ford 5.4 supercharged anyday !! Yes,I know the SRT is no longer made,but it is the fastest production truck ever !!!!

Bill,also compare a 2003 Dodge 345 hp to a 2003 Chevy 5.3 with 285 hp. A 2003 Dodge will and does run all over a 2003 Chevy 5.3..as the Chevy runs high 16's-17's in the 1/4 its equal or close to a 2003 Dodge with a 4.7 not the Hemi..As the 2003 345 hp Hemi is a solid 15 second truck in the quad cab configutration.

Bill,a 390 hp Dodge runs all over a Ford 5.4....obviously if you beat a Dodge he was not racing you or he had a 4.7..You are full of it..

I disagree with Tyler, a truck doesn't have to have 4x4 to be a truck, I buy my trucks for towing my camper and ski boat, not for offroading, if I want to go offroading I'll get a Jeep, not Pickup. Are you saying that Semi's are trucks since they don't have a drivin front axle?

If people have rams here where i live it has a hemi and i drove the 345 hp hemi before and it was nothing special i have a supercharged truck my brother in law works at a ford dealer he does all the work on my truck end of story !! i read on trucktrend.com that the hemi ram 390 hp is at 0-60 mph at 7.0 sec the new rt ram is at 5.9 sec the foose f150 is at 5.6 sec i have 20 more hp than that foose so ya i think i can win lol david shift kit the hemi is not god almighty thats all i have to say if it was the 2010 camaro ss would not beat the challenger srt8 then would it.

The arguing is ridiculous, and really shows lack of understanding of the functioning of engines let alone US fuel rating system; understanding how the FTP works in the US, understanding of VVT and emissions, understanding of hp and tq first in NA applications and second in Charged. Or understanding of technology level effects on emissions and power peak, specific and curves. This makes 2 valve cam in block motors achieving same ratings as 4 valve dual independent cam phased motors, look even better.

High hp means nothing for towing and no NA will have a flat torque curve period. SORRY and a twin turbo motor achieving 100 hp per liter is not impressive either.... 2.0L ecotec 260 hp... released years earlier.

Don't even start on dodge there is a reason Fiat is now in trouble. Dodge's aren't worth using as a paperweight, hundreds of problems. Way behind.

Hey Blob you should do everyone a favor and go find one of your GM propaganda web sites to post your B.S. on! No one here really cares about your inflated numbers!! FORD sells more trucks world wide than anyone else. F Series has been the number 1 selling truck on the PLANET for the last 32 YEARS!! PERIOD!!! I work in the auto industry and am privy to information that you could only dream of seeing. More municipalities buy Ford products than GM. And don't give me the price is cheaper because it isn't. If that was the case the wealthy communities would buy a GM if money was no object. Guess what? They buy Ford because it is a PROVEN and RELIABLE fire truck, ambulance, DPW vehicle, Police Vehicle etc. So get over your B.S. Gm crap the real number speak for themselves. I hope you enjoy paying higher taxes to bail out a company that is such a winner!!!! Ford didn't need any money and they are gaining market share. GM and Dodge continue to lose it! So if they are so well off why are they still so broke????????

GM & Ford often cite their vehicles as having the best fuel economy, yet strangely, their models with good fuel economy have low power and displacement, and their models with good power and some displacement, have poor fuel economy. It wouldn`t even be fair to call this type of advertising a half truth, because it`s really truly misleading.


@Scott - I agree with you about the deceptive advertising. It's why salesmen, lawyers, and politicians rate at the bottom of the list when it comes to trusted professions.
Spin Doctor's would refer to it as " selective dissemination of information". Legally, they are not lying to you, they just aren't telling you the whole story!
Pathetic, isn't it!

You guys are forgettin one thing here Silverado 5.3 15/22 Dodge Ram 5.7 14/20 Ford 4.6 15/21... Now Ford hittin on all 8 cylinders, Chevy and Dodge you hittin 4 cylinders to get that extra mileage...Its ashame to to hear all the whinnin of whose the best. My goodness Fellas grow up!!! I'll stay with the V-8 that hit on all cylindes. I'm not judging anyone, just givin my side of story... Have a nice day!!!

Oh 1 more thing any V-8 you drive we will not get good mileages, because we all have lead Foot!!! LOL

Sure are a lot of angry people posting comments on this website. Seems like every article is followed by a GM vs Ford vs Dodge pissing match. I am a mechanic and have worked for a dealership of each of these brands. I can honestly say that regardless of the brand you buy you will probably get a very good truck. People always say certain brands are crap because some friends step brothers mothers kid bought one and something broke. These stories are usually B.S. and dont reflect the experience that the other hundreds of thousands of customers have had. If all the vehicles produced by these companies where as bad as the ones in the stories none of these companies would be in buisiness anymore. End of story.

It would be nice to read the opinions of people regarding the story for once, not reading GM sucks, FOrd sucks, Dodge sucks over and over and over and ........

Further to my comments posted above, I would think Mike Levine was living in 2007. You know, GM is using variable valve timing, FINALLY, while Toyota is using DUAL VARIABLE VALVE TIMING to put out a truck with big HP and big TQ, with slightly less displacement, with pretty damn good mileage for it's displacement, with better real world ratings than a GM model that cuts to 4 cylinders with more displacement, and more power & torque then that same model, all on regular gas unlike the bigger 6.2 Liter GM is now pushing which requires premium and is only available in lmited models & trims, and this 5.7 L Toyota engine & tranny are available throughout the entire Tundra line up. Oh, and that 6.2 liter is just matching the Tundra's performance with more HP and TQ - Maybe they have a drive train problem?

Mike when are you going to write an article on some real engine technology that could change trucks. You know, encouraging them to utilize dual variable valve timing, the benefits of dual overhead cams which Toyota has been using in their trucks since 1995 (wow, Ford came out with a 3 valve in 2004, wow, that's such big news when Toyota had a 4 valve out in their Tundra in 2000 and their T100 in 95, and the Tacoma in 95). Wow, they came out with variable valve timing in the Ford F-150 in 2004, while the Toyota 4runner in 2003 had variable valve timing on it's 4.0 V6, and subsequently the Tundra in 2005 (4.7 L V8, 4.0 V6), and the TAcoma in 2005 (4.0 V6).

Dual variable valve timing is the reason why the Toyota Tundra has engines are as potent as they are yet with acceptable fuel mileage for the power and torque they churn out for a given displacement.

Maybe you should have written this article in 2004 about the Ford? But it's 2010.

@Scott: I think we did exactly that in our deep dive review of the new Toyota dual VVT 4.6-liter V-8. Perhaps you missed that story?

http://special-reports.pickuptrucks.com/2009/02/toyota-debuts-new-46liter-v8-for-tundra-with-exclusive-video.html

Yes, we also covered VVT in the F-150 in 2004. But neither made 22 mpg out of a NA ICE motor. That's pretty cool.

As for GM, I personally expect to see their VVT for OHV engines continue to develop. My speculations is cam-in-cam VVT. Well see.

Unfortunately, Scott, every day can't be future powertrain day at PickupTrucks.com.

If your obsessed over mpg get a prius. Ford, Ram, and GM make good trucks and it all boils down to preference. I know many who drive all makes and though they might be set in their beliefs the truth is they all break and there is something to be said about how the owner treats it. If you thrash on it or neglect maintenance then you will have problems.

Its good to see the big 3 focusing not just on mpg but delievering perfomance and fuel economy. Who would have though 10 years ago that today 400hp is the new standard for pickups and getting 20 mpg.

Wait didn't we just cover this in the other post about sales numbers? Going off the top ten list Ford sold more pickups F series and Rangers vs. Chevy, GMC, and Colorado combined? Almost 10,000 more. Keyword there being PICKUPS not CUV's and SUV's that GM likes to include in its numbers just so they can say "We sell more trucks than Ford"... Trust me I don't blame GM, its a good sales tactic on their part but the numbers don't add up when you actually add just pickups and not everything else.

As far as their new motor design, I'm happy all my (and your) money is going somewhere to help them out... on technology thats already at least 10 years old. I might not have a say what the government does with the money I give them but I do have a say with the money in my wallet and it will be spent on a FORD!!!

Oh and one more thing. All the truck makers make a good product. IF you like a Ford then drive one. IF you like Chevy/GM then drive one. IF you like a Dodge or Toyota then drive one. You can come on here moaning and complaining but the bottom line is everyone on here already has a chosen favorite so they just need to stick with what they like! Trust me I have done my fair share of complaining and it don't get you nowhere. Everyone makes some valid points but all this bickering just get old...

Wow.. Chevy is still using their overhead valve design they came out with in 1900. Thats epic.

Who gives a s**t bout gas milage ,you want that buy a car .We buy trucks for power and the technology with the new motors came along way. I have a 2010 gmc crew cab 4x4 slt with a 6.2 and i have yet to be beat in race or out pulled by another gas motor.My brother has an 08 duramax with an 80 hp tuner and i still beat him by two truck lenghts. bring on any ford,dodge,or a p.o.s tundra.

ford may be best selling truck for over 30yrs. but if you put the two gm truck brands together chev/gmc they sell close to what ford and dodge together do!!!

if any of you knew anything, you would know that the hemi is a beast, and gm and chrysler are on top with truck V8s
sure, ford gets a lot out of ecoboost, but hemi and vortec still dominate at the line with power and dependability, and Cummins is always going to be the diesel king-that 5.4 ford would be blown away by a gm 4.8 vortec or dodge hemi-that 5.4 is a joke, so bill is blowing himself

You can talk your face off about i blow the doors off this and i am faster then that i didn't buy my truck to go faster then anything other then a moped. If it goes 100 km an hour I am fine with that. What i care about is how much it can pull. It's a truck I want power not speed.



The comments to this entry are closed.