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

In the market for a new truck this spring.

Gas milage isn't even in the top-ten on my list.

This is a joke a 2010 Hemi in a 1500 that makes 390HP is rated at 20MPG with a 5 speed tranny and the little 5.3 that makes 315hp with a 6speed tranny gets 21 Wooohoo very imprssive GM!!!

The hemi lol dodge is a joke i remember when they first put that hemi in like 2003 model year 345 hp its a insane engine there dealers said all the time and that little 5.3 took it everytime in drag races where i lived hemi is overated i will be sticking with ford for life my 2008 harley davidson mops the floor with that crappy 390 hp hemi and i got 5.4L lol i love takeing the doors off of dodges at the lights

@ Bill

I would take that bet anytime!!!

lol somebody want there rusty old dodge doors blowen off ha

Quote - "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."

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. Fuel prices will rise again. No one really knows what the maximum price people will be willing to pay for gasoline/diesel. I think we were close to that point a few years ago. I saw a large number of 6L and 6.2L engined pickups collecting dust on car lots when the fuel price shot up.

Well the 5.4L no matter what people try to spread, is a good motor. It has the lowest HP, yet the trucks seem to keep up in towing and acceleration. If you want to race though, get a car.... If you want to compare trucks, try using them for what they are intended for.

Ive always had a bit of heart burn with the VVT technology since the 90's. While it is the next logical step it is not a true variable timing since everything still runs off the camshaft. The goal should be for all valves to operate independently based on programing, conditional inputs, feedback and mode.

Although i have to admit it looks like the new 5.0 ford is getting a lot out of the current setup judging by the HP peaking at High RPM. This is indicative of a flat torque curve.

Just to add fuel to the fire. Chevy gets 22mpg highway running on 4 cylinders, with a tonneau cover, a super low front valance, 6-speed tranny, High 3.08:1 gear ratio with derated towing 7,000lb, Low-rolling-resistance tires ,and VVT. Everyone else gets 20-21mpg highway running 8 or 4 cylinders with 5 or 6 speeds and much higher towing capacities.
Not all that impressive when you compare alternatives.

this is for the tone i live in alberta canada no way a car can go where i need to go i use my truck to haul my arctic cat mountain sled but everyone here has some pretty hot trucks got to stay in the click i got the money i can do anything i want with my truck even race free country

@Bill,, There is no way your 5.4L ford can blow away a dodge hemi. Hemi would blow your ford easily. My brother has a 5.4L ford and it can't keep up with my sisters 5.3L GM. I drive a 08 Ford super Duty 6.4L diesel and can't keep up to either of them cause it's always in the shop for repairs. If i were to get a gas pot i would definatly but a dodge with the hemi, solid engine in a solid truck.

supercharged dude 470 hp lol i get 14.7L per 100 km hemi so sick last 70000 km and dead along side the road only ppl on budgets bye dodge cant even give them away here in oil country my brother in law dad bought a new diesel cummins and the tranny went after 7000 km pulled a camper 1200 km from a wedding back to his place ya thats something i would want to buy ugly crap!!!!

Bill you must be drunk or got to much exaust fumes from youre engine. I have o9 himi with 3.90 its a great truck to drive , you could never keep up with hemi stop spreading lies just shut up when you dont know facts ....

yeah whatever dude lol thats what u keep telling yourself o ya and its a roush supercharger under the hood ya they do make them for the 5.4L

@bill, you have no idea what you are talking about. quit making up stories. I know way to many guys with hemi and cummins and they don't have any of the troubles you have made up. Loggers here use lots of cummins trucks because they are heavy duty and get the job done, and they are far from ugly trucks. Next to my 07 duramax they look pretty darn good and can pull anything i can. Go smoke another joint and make up more b.s stories punk.

Take this Ford!!! Fords are like a FAT girlfriend because you need to constantly feed them food and or fuel.



Flex-fuel Vehicle Flex-fuel Vehicle
Estimated New EPA MPG
New MPG tests are more realistic
E85
11
City 13
Combined 16
Hwy

Gasoline
15
City 17
Combined 21
Hwy

E85
10
City 11
Combined 13
Hwy

Gasoline
14
City 15
Combined 18
Hwy



MPG Estimates from

bs stories well i work up in fort mac in the oilsands and all flint energy, pacer, suncor ,cnrl ,ensign drilling drive ford they are not crap !!! and u can think its bs storys i really dont care lol i love battleing with dodge fans hemi is almighty god and all have to be scared of it it makes the best mpg and can beat anything in its path well if that was the case ford would be in number 10 on the list of best selling cars and truck for 2009 not dodge

Well Lou i have to say i agree with your comments on trucks having enough power and fuel economy is a major concern with consumers now. 300 plus hp and 600 plus ft/lb torque is plent enouph to get your load from a to b. Designing a combustion that uses all the fuel injected and achieving low heat to keep NOx low is way more difficult than making more power.

22 mpg in an "XFE" truck with a 6 speed and granny gears is pathetic. Way to go, GM engineers, finally putting 20 year old technology into your trucks (better late than never, huh?)

Lou is right, if there is one thing that is certain, it's that fuel prices will go up again and stay up. Hopefully GM will come up with better stuff that recycling old technology under new acronyms by then.

@bill there you go with more B.S. , I work for Suncor as a mechanic and drive Duramax field truck . Get it right next time. Yes lots of company's use Ford but as of late they are not happy with them and buy them because of good fleet discounts. My personal truck is also a duramax because i have to pay the repair bills out of my own pocket and don't want to waste my hard earned money on ford repair bills. My brother in law Pat also was just given a Dodge HD for service truck because his sector has had enough of ford problems, also from Fort Mac.

I am with bill on this one i have a foose f150 and there is no hemi that can take it dodges are fat and slow hemi is a big joke

lol well i am pretty sure i saw alot of harley and all ford trucks at wapasu camp lol are u at firebag frick dude bs storys wow if u are u must be out of work right now that place is closed lol are they starting stage 3 soon i worked at the sru and vru plant building it in 2008 at stage 1 and 2 for ft services ya i think i am not telling bs storys thanks chas southern alberta is ford country!!

Any GM news is appreciated, but we would really like to see information on the 2011 HD front suspension and the 7.0L gas engine!

quite arguing like little children!!!!! screw gas engines!!!!! CUMMINS DIESELS FOR LIFE!!!!!!!!!!!!!!!!!!!!!!

Apparently snowman speaks for everybody in the field. Thats odd nobody told me he was my union rep. Was it in the last newsletter?

If you are going to buy a truck are you really concerned about gas mileage? For that matter do we really need a motor bigger than a 6.2L? I mean its nice for bragging rights but if you need that much power all the time and if you are doing actual work with said truck then you might as well get a truck with a diesel in it.

There is no 5.4L that is going to beat a Hemi unless its been tuned up or supercharged. Hate to tell you that but thats a fact. Now if you had a Foose or Roush F150 then yea you probably could take on a Hemi any day of the week.

Lastly although I didn't agree with most of what he said but Bill has a point. Every one I know that has a Dodge Ram that has had problems with them its either been two things, the rear or the tranny. I know of 4 or 5 guys now that had to have this fixed on their Rams, one is on his 3rd tranny. Maybe its to much power from that Hemi? But one thing I will never do is call a Ram ugly. Its the best looking truck out right now.

With the current state of things with GM and Dodge its going to be real interesting when the 2011 trucks come out. Ford having the new 5.0L and 6.2L in their trucks will finally put to rest all the complaints about the current motors and push theirs sales further up.

@Bill a 5.4l are u serious blow off doors ill take u with my heavy duty dodge cummins

u can supercharge any ford truck it dont have to be a foose or roush f150 they sell the superchargers at any roush ford dealers it cost me 7500 bucks for the roush supercharger headers and daul exhaust system i know a stock 5.4 L cant beat a hemi thats why i put alot of xtras in it i dont care about gas milage its 95.9 cents a liter here i have a 125 l tank and the tranny story is true he bought a 2009 2500 cummins and drove his camper to my sisters wedding and he had no 2 or 4 gear the dodge dealer here fixed it after alot of battle and he is a big dodge guy

jason lol maybe in your head

I think jason needs his rusty dodge doors blowen off the foose is always here to take on any takers

@chas and bill, if you guys know anything about power you would know that you can't get near the power from a gas pot as you can a pumped diesel. Jason could easily blow you guys away with a modified cummins. you guys will never see 900 hp and 1500 ft/lb of torque that you could get out of a diesel. Dream on chas/bill (same person) and get some real balls with a diesel. Bill , the way you type you must have quit school in grade 3. Gas engine blow away a diesel, ya right. What name are you going to use next chas or bill or......????

@snowman, I know what you mean by how some companies only buy Ford b/c of the cheap fleet discounts. Hell, at one time, my relatives who are in the construction business, drove nothing but Ford 3/4 ton diesels. But when the new Duramax's came out in the Chevy/GMC HDs in 2001, they changed over to GMC. And since then, that's all my relatives drive is GMC.

Considering that Ford has been using the VVT technology since 2004 with the 5.4L engine quite an accomplishment GM!!!! It only took you 6 years to try to catch up to the truck leader!! Any for those of you guys with a Dodge Ram the whole truck is a big load. Reliability? Something Dodge has never been known for or known anything about. Why do you think they always get piss-poor ratings from all the car magazines?? It can be summed up in 2 words: "THEY SUCK". The should have gone out of business a year or so ago when they went begging to Washington for TARP money that they have no intention of repaying by the way! The only 2 American companies the challenge each other year after year is Ford and GM. That is how Ford determines on how NOT to build a vehicle. Keep up the good work GM, maybe in 20-30 years you might be able to catch up to Ford.

I think GM is full of crap with there MPG ratings! and HP ratings. My company owns 2008 chevy 2500HD's with a 6.0 gas motor. 3.73 gears and a 6 speed trans. It is the biggest peice of crap!!!! Unloaded highway MPG was 11.0 MPG. I won't even talk about trying to tow a 10,000# trailer with it beacuse it's pathetic! I have also own a 2007 F150 with the 5.4 It also had trouble pulling a trailer that weighs about 9300# the MPG with that truck was about 13 MPG.
If you want good MPG Buy a deisel they are made to Haul and get great MPG unloaded OR Loaded!
Variable timing, Just more stuff to break and have a truck be in the shop for repairs Regaurdless of Make!

Yup so spend and extra $10-$15K and then get........... 13 mpg Yahoo new diesel!!!!

Is is NOT VVT, it is VCT.
http://www.mechadyne-int.com/vva-media/display-media/dual-equal-cam-phasing.gif/400/400/dual-equal-is-always-a-compromise
GM's Atlas engines have variable valve timing, on the exhaust valves only.
If GM & Chrysler spend more money [and Ford with the 4.6/5.4] for a more sophisticated phaser, and concentric camshafts, then they will have VVT.
http://www.mechadyne-int.com/vva-media/display-media/dual-independent-cam-phasing.gif/400/400/dual-independent-cam-phasing-gives-total-flexibility
http://www.mechadyne-int.com/vva-products/concentric-camshafts

Hay Ford lovers, go to the www.fueleconomy.gov and you will see the 5.3 liter is rated at 21 miles per gallon on the highway vs Fords 5.4 liter that is rated at 18 miles per gallon on the highway. And for the idiot that said GM puts these ratings on their trucks is completely false! The enviormental protection agency, aka EPA puts the ratings on all makes.

Don't believe me, look it up yourself on fueleconomy.gov.

GM sells the most trucks and they get the best gas milage period! These are the facts and only the facts. So let it be written, so let it be done!

Bob, Don't be calling people idiots. The Chevy Silverado 5.3 that gets 21 mpg right now is the XFE model . Ford's 5.4 SFE model also gets 21 mpg. You can read it on the Silverado website.....15/21 for the Ford F-150 they are comparing it to. Now, Chevy Silverado is one 1 mpg better at 22 mpg. Wow. Big deal.

Hay Dave, YOUR WRONG! The XFE model is ratted at 22 miles per gallon. I said the person that said GM rates their trucks on fuel economy is a idiot! The EPA is responible for the ratings. Now stop trying to correct me and look it up your self on fueleconomy.gov, the Silverado is 21 miles per gallon with their 5.3 liter six speed transmission and the Ford's 5.4 liter with Six speed transmission is 18!

The Chey Silverado is 3 miles per gallon on the highway and 2 miles per gallon better on combined city and highway driving! These are the facts and they are posted on the Fueleconomy.gov and Yes, Dave that is a BIG DEAL!!!!

The 2009 was 21, like I said, it is now 22.

F-150 5.4 15/21
Silverado 5.3 15/22

Big deal

F-150 15/21
Silverado 15/22

This is all a bunch of BS. So they produce one version that does 22, that no one will buy... big deal. Get the std models getting over 20 w/everyday driving w/o adding $5,000 to cost, and 'll be impressed.

BTW who would buy a XFE? With that gearing, just hook up a utility trailer to your saturn! Or put a electric motor on yoru wheelbarrow.

For the record Dave, it's not the 5.4 liter engine that is rated at 21, it's their 4.6 liter and only their fuel economy model like Chevy's XFE model that is 22 mpg. The 5.4 liter is 14 city and 18 highway and this is posted on fueleconomy.gov!

Take off your Ford colored glasses Dave and look it up yourself. The chevy beats the Ford and The Dodge in fuel economy by 3 miles per gallon on the highway and 2 miles per gallon on combined fuel economy. So chew on those facts Dave!

Hay Dave, The Chevy's 5.3 liter engine on their XFE 2wdr is rated at 15 city, 22 highway vs Ford's 2wdr 4.6 liter that is rated at 15 city and 21 highway. Once again the Chevy BEATS THE FORD!!!!!!! You can't stand it can you Dave? A Chevrolet Sivlerado with a 5.3 liter engine beats a Ford with a 4.6 liter engine!

Chew on those facts Dave!!!!!!!!!

@Bob Yeah you Government Motors boys are all alike. Wow you know how to look you EPA ratings. Don't forget my ignorant friend those ratings are based on IDEAL driving conditions and DO NOT reflect actual real world traffic conditions. You sound so angry why the hate towards us Ford guys? Sounds like you need anger management classes and stop preaching that EPA ratings are Gospel because they aren't even close!! Or is it because you like an inferior product that makes you hate. You are probably one of those idiots that rubs one out everytime Howie comes on the TV and says you left your man step down. Sounds like you are jeolous that Ford is #1 and will always be #1. Don't start that crap they seel more trucks than Ford because THEY DON'T!! You are one of those guys that has to include GMC numbers in the mix to make yourself feel good. Get a clue pal!

You guys are right it is not the 5.4. I corrected it in the second post.

Silverado XFE 5.3 15/22
F-150 SFE 4.6 15/21

Silverado LTZ 15/22
Silverado LT, LS, WT 14/19 2wd 13/18 4wd

So the Silverado is a little bit better in some and not in others, and it appears you have to go with the LTZ or the SFE to get the 15/22.

I got all of these numbers from Chevy's site.

The one thing I hate about the Silverado is that you can not get the Chevy crewcab with a 6.5' bed. You can only get it in a short 5' bed which is not good for hauling. I'd rather stick with the longer bed and get less mileage.

Have a nice day.

No me and chas are not the same person i guess anyone that thinks dodge sucks is the same person lol ford trucks77 is right on alot of stuff ford will always be number 1

Hi Bob,
I only drive 4x4 trucks so the extra mpg of the 2wd is pretty much useless for me with any manufacturer.

Yes, GM does sell more trucks than anyone including Ford! The GMC Sierra and the Chevy Silverado may have different looks and design but dimensions, drivetrain and powertrain are identical! They even build them in the same plants!! So don't give me this crap that there not both GM TRUCKS!!!

Some of us here can't accept the fact that GM sells the most trucks and gets the best fuel economy period! end of story!

So take that Ford and Dodge lovers! and for the record the EPA did change the fuel economy ratings in 2008 to make them more real world. So quit saying their not even close.

GM #1 IN SALES AND FUEL ECONOMY and everyone else is sucking hind titty!!!!!!

GM sells the most trucks at a loss, is losing market share, and their XFE 2wd Silverado went from 21 mpg to 22 mpg. Wow!!!!!!!!!!!!!!!!!!!!! It's party time in GM land.



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