2014 GMC Sierra Testing Proves Tailgate Up Is More Efficient

Gmc-sierra-wind-composite

GMC says the 2014 Sierra spent more time in the wind tunnel than any before it as fuel efficiency becomes an increasingly important piece of any successful new vehicle.

The engine can be tuned, the truck can go on a diet, but tweaking the shape of a vehicle so air flows most efficiently is one way a relatively traditional shape like the pickup can gain mpgs.

The 2014 Sierra has a new air dam up front and ducts between the grille and radiator to improve air flow. But it was the testing of the bed that revealed one interesting piece of data that could stop truck arguments cold.

According to GMC's Diane Bloch, an aerodynamic engineer, leaving the tailgate up is more efficient than leaving it in a lowered position.

It seems that with the tailgate up, the air flowing over the cab falls downward and then pushes forward against the truck. With the tailgate lowered that air escapes and doesn’t add any benefit.

Bloch also advised against nets covering the back of the truck. "Replacing the tailgate with an aftermarket net is worse than having no tailgate at all," Bloch said in a statement. "Imagine dragging a solid object and a fishing net through water. The net is going to require more muscle."

Comments

Old news.
Jeep found this out in the 80's.
There used to be a road race series that raced compact trucks.
The Jeeps were the only ones using tailgates.
They were very competive.
I also thought Myth Busters put this to rest.

GM is just know learning this, Wow.
Just shows how up to date they are with AERO.

But one look at the new Chevy grille.............

Ford said this same thing in some of their videos years ago too. That's why GM screwed a plastic spoiler on their tailgates after that, since they didn't design it into the truck earlier. Now the GMs have the spoiler incorporated into the tailgate design like most others.

Here's a Ford video from 5 years ago.
http://www.youtube.com/watch?v=1YL423MHtLc

Wow quality truck is hard to accept for some people..??nice job gm,,

Looks like a FORD in the front but man the rest of that thing is BUTT UGLY!!

Any additional specs released along with the regular cab?

I really want to see the EPA figures on the V6

Nice truck but talk about stinkbug posture. Ass up and nose down.
I am surprised that companies don't offer a bed cover as standard equipment to gain 3-5% mpg.

@ lou

Ram's high MPG model does have a cover :)

I think Ford did the same thing back on 2008-10

Let me ask y'all a silly question: For all that you know 'tailgate up' is more efficient, how many pickups do you see on the road with the gate down and/or a net across the back?

Yes, Mythbusters proved this several years ago using both hydrodynamic experiments and a simple one-on-one truck experiment using two identical trucks and fully-topped-off tanks and driving 'til they stalled.

@ devo340

Yeah, MythBusters did put it to rest.
Some people hold onto their idiotic notions despite the scientific evidence placed in front of them.
I've got a friend who is convinced he can get 30mpg from his four banger in his Frontier by taking the tailgate off and adding a cold air intake.

The cold-air intake might work--but because he's eliminating the tailgate entirely, his numbers will remain stable at best and probably go backwards.

Who would drive with the tailgate open if your not carrying a long load? I mean it would flop up and down when you hit bumps not to mention it will get pelted with rocks thrown up by the rear tires.

Diane is just learning this huh? Wow. As others have already said, this is old news. I saw the Mythbusters thing too a long time ago. Between them rebadging Nissan vans for the Chevy dealer across the street and this news today, I'm starting to wonder why we gave them all that cash as well. I don't like the rake of the truck either. Everybody does it but I notice GM tends to over do it. Most guys have to get a leveling kit installed then. This truck's ok, I think the Silverado looks better now though. Just not big on the GMC's.

Can someone point out where does it say that GM has just learned about this?
FordTrucks1, I will use you as an example. One day you write some really interesting stuff, the next your just the second biggest troll on this site (Frank will always be #1)

PUTC is in fault here as well for not reporting everything that was said.

Here is what GM was actually trying to point out:
"In regards to the aero tuning of the 2014 Sierra, these images show just how far GM has gone in maximizing the truck's fuel efficiency and reducing its noise, vibration and harshness (NVH) levels. Interestingly, the press release shows visual evidence that keeping the tailgate up is best for aero – there's always been some Mythbusters-level contention about such things –but GM also says that adding tonneau covers (preferably soft) and running boards can also help improve the overall aerodynamics"

Nice little truck by the way, but I would like to see a Silverado version of it.

Wow Ohio people sue ford because problems whit ecoboost v6????check detroit news.....

I still swear by the pro net tailgates. I've used the same one on all of my FORDs since '92. Guess I never end up putting enough miles on 'em to wear the net out since I spend a lot of time in the shop.

Son of a Gun that things ugly!! Silverado can't be much better. Sorry folks but ugly is the word here.

The grille screams 2005 F-250. SMH!!

"Bloch also advised against nets covering the back of the truck. "Replacing the tailgate with an aftermarket net is worse than having no tailgate at all," Bloch said in a statement. "Imagine dragging a solid object and a fishing net through water. The net is going to require more muscle.""

According to Myth Busters the mesh was the most fuel efficient.

@Miath

Wow and a guy in Texas sued Cummins and Dodge because of faulty engines... WOW

I just wish rear bumper step wasnt standart. That kind of ugly.

Nice truck but talk about stinkbug posture. Ass up and nose down.
I am surprised that companies don't offer a bed cover as standard equipment to gain 3-5% mpg.

Posted by: Lou | May 16, 2013 5:32:13 PM

That is a 2wd TRUCK LOU!! MOST EVERY 2WD TRUCK THAT I HAVE SEEN IS LOWER IN THE FRONT AND HIGHER IN THE REAR. That is why MOST ALL FORD TRUCKS SQUAT TO THE GROUND WHEN YOU PUT 200 LBS IN THE BED OF THEM!!!! They look like A DOG DRAGGING ITS BUTT ON THE CARPET. That's pretty fitting when you really think about it. Pretty much all Fords that I know ARE DOGS!

Actually, Goodyear ran tests back in the 70's with a Ford F150 and found with the tailgate up it got better gas mileage.

@Vulpine. A cold air intake? Really?

If cold air intakes really worked to save fuel, don't you think Detroit would have used them starting many years ago?

More power? Maybe. Better FE? Not.

Same with mufflers. A muffler costs almost nothing to make. Don't you think car makers would put the most efficient mufflers possible on these cars/trucks? They spend MILLIONS every year trying to squeeze better economy out of these systems. Cold air?

GM also gave some advice in there press release, as far as using a tonneau cover and running boards. Saying that a soft bed cover will help smooth the air traveling over the truck and running boards help lower the coefficient of drag.

http://www.chevysilveradoblog.com/chevrolet/gm-proves-that-tailgate-up-is-more-efficient/

@michiganboob, yeah this truck is what fell of FORDS as#$ when they got done dragging there butt on the carpet, called it a DINGLEBERRY!!

@papajim

Actually intake and exhaust work can and usually does make a car more fuel efficient. Engines are big air pumps, when you can get more air through it easier and smoothly efficiency gains are usually found.

Pat Goss just did a short show on that and how intakes and exhaust work can help increase fuel mileage.

The big reason manufacturers don't/can't is noise/emissions. Look at a stock car intake, see all the baffles splitting off the intake pipe? Those are to make it quieter and it disrupts the air flow. Ditto with the exhaust, look at how many times and what the exhaust gasses have to pass through on the way out of a stock heavy muffler. If they could manufacturers would use a straight through muffler like a magnaflow for power and economy, but the sound is why they can't, not to mention emissions even though most mufflers are emissions legal. On my GTO the magnaflow was almost stock quiet at cruise but being straight through at WOT it had growl. Smooth air in and out is best, stock cars have the air going through all these crazy paths.

No on a different note, to take advantage of the new smooth air in and out a tune would be beneficial, but then that usually requires more fuel for power and to make use of new mods. On a stock car with just the I/E you aren't getting much if any mroe fuel and your economy usually does go up. Now if you do it for the sound you might drive with a heavier foot and negate those gains you should get because you are hot footing it around more, that happens to many people with their new mods...

I always laughed at these dolts with no tailgate,tailgate down or those aweful looking nets ,all thinking they get better mpg !

@Lou,

I actually like the looks of trucks with the back up higher..Every truck with a levelling kit looks aweful,and when they add a load,the back end is down,and laughable.RAM 1500's sit so nice ,the back up a few inches,really makes the truck look mean,not to mention they handle corners better with a lower front,higher the front you go off in the weeds...

Yep,like my classic cars (mopars torsion bar is great 5 minutes you can raise or lower the front suspension to any height no taking parts off,no spring cutting easy 5 minute job to do both sides )front end is lowered few inches from the back,top of front tire even with the front fender/lip opening (back not jacked up) a nice 2-3" rake makes a rwd car and any truck look alot better.

Level trucks look bad and over time,back end is lower than the front when they ad a levelling kit,I see it all the time,any brand of truck front end is higher than the back,and they have an empty load ! I drive past a mid 90's GMC everyday like that and a 05 or so F-150 with nothing in the box,I see everyday out my office window the front is 3 inches higher than the back,that my friend looks extremely bad !

A truck with no gate is like a person with no underwear. IT'S GOING COMMANDO!

@tyler Intake and exhaust improvements on race cars are completely irrelevant to a discussion of street machines except to discuss theory. A NASCAR Cup racing engine is running at over 8000 rpms. In that world, resistance in the air stream is a huge negative factor. In a half ton pickup, the drivetrain is designed to deliver performance at engine speeds between 1500 to 3500 rpms. At those speeds the size of the exhaust pipe or the internals of the intake manifold have been precisely calibrated by automotive engineers to optimize results.

If you drive your average pickup at engine speeds over 5000 rpms for very long it's gonna be toast, but your mileage may vary.

@Tyler: I've discovered with many different vehicles over the years that a high-flow air filter alone can add up to 10% to the fuel economy--that's from 2-3mpg that I've seen on a '96 Camaro, an '02 Saturn Vue and a 1990 Ford F-150 5.0L. That's not even changing intake path.

However, in the extreme heat of summer that Camaro was sluggish at best. My Vue and other cars showed the same characteristics. Sure, it still carried somewhere around that 200+ horsepower the 3.8L V6 offered, but only on open highway with only limited traffic around. Same roads when the outside air was cooler brought in noticeably better performance. So I fully believe--simply through personal experience--that cold-air injection does benefit performance and economy.

@Vulpine, Tyler - IIRC, there was a test done in one of the truck mags a few years ago with a Ford F150 and 5.4. They put a cold air intake kit on it. As Tyler pointed out, the vehicle sounded louder as the cold air intake made more noise, especially on hard acceleration. Vulpine is also right as they showed a modest 3-5% gain. They figured that it would take 5 years to break even on the cost of the mod by saving gas. The truck showed a modest hp gain.
I can't recall if they said it affected the warranty. Sandman4x4 did have a negative experience with a CAI on his EB F150 and had to fight to get warranty coverage.
I'd say buyer beware.

@CanadianRamowner - some people like the ass in the air look, I don't.
I don't get those leveling kits either. Goes to show that most people buy trucks for show as opposed to work.

Which engine do you have in your new air ride Ram? My local dealer only has a few 3.6 V6 trucks in stock with air ride or 8 speed. I have yet to see a 5.7/8sp with or without air ride.
Sounds like you have some cool rides.

@Bitchagainbob - did I say that I hated the truck? I like the new GMC's. They fixed the areas that I had concerns about. Odd, if the GMT900 was such a great truck (as you used to argue), then why did they change almost everything?

Doesn't your wife get upset with you for dragging your butt on the carpet?

It might be the photo angle since the truck looks lower from the front than from the rear.

I agree about the level look, they always look nose high to me, People measure the distance from the fender to the tire and think if its the same front and back then it's level, wrong the wheel wells not the same front to back and the sheet metal is put on the truck to fit a slightly lower front end.

Dear staff of pickuptrucks.com,

have you guys started monitoring and removing posts? I recall a post earlier this year or late last year that stated you guys would start moderating, but I don't notice much change so far.

Thank you for reading this, in advance!

@ Kemo: Yeah, I remember that, too, but it seems to have gone the way of a typical New Year's resolution. Prove me wrong, PUTC. Please.

Regarding the actual subject matter at hand, all I can say is, it must have been a slow news day (I've been away from the computer most days this past week, so I haven't been checking PUTC religiously) if what counts as news is something the MythBusters reaffirmed several years ago and Goodyear discovered decades ago.

As far as the "stinkbug" posture of that Sierra, a few things to consider:
1. The photos were taken at a lower angle in an attempt to give it a more aggressive look.
2. This particular model is a 4x2; stock 4x2's will always sit higher because of the lack of a front transfer case.
3. Those of us who use the bed of our pickup for something besides groceries appreciate a higher rear stance; our '08 F-350 doesn't even squat with 1200 lbs. of seed, but levels out real nice when you put a gooseneck on it. Now if Ford would only do something about the F-150's ludicrously high bed sides...

"FordTrucks1, I will use you as an example. One day you write some really interesting stuff, the next your just the second biggest troll on this site"


Interesting comment from the Greg's,Tyler,Sierra's,Bvonscott,Bob's,Jim's etc goof. Just another GMI locker room towel boy. Troll? Hardly. Everyone knows this is a GMC fluff piece and has nothing of substance. It must really bother you that a Ford guy like myself happens to like quite a bit of Chevrolet stuff. That doesn't mean I'll give a thumbs up to everything GM does.

Trucks have had a rake in them for quite some time. For those of us that use our trucks to haul, it means the rear levels out with a load... rather than sagging the rear end lower than the front with miniscule loads.

Cold Air Intakes are very simple, as the engine is an air pump, it just stands to reason more air in, and more air out, means the engine will be more efficient, and the only reason the manuf. do not use them is the noise standards from the EPA, and what Tyler said is true, he said on a stock car, what he meant was a car or truck that is stock, not a Stock Car as in racing car! even if you use a K&N air filter, in your stock air box, you will get a small benefit, I have used Cold Air Intakes on all my vehicles, cars, trucks, and motorcycles, all of them got better MPG and on one of my bikes, I get an 12% INCREASE in HP and 10% in tq, on a dyno! and when you are talking about 118 hp to start, that is a big jump! that is proof enough for me, PAPA.

GMC = GovtMoCo. WASTE of AMERICAN TAXPAYER MONEY! PERIOD. Oh how Sierra drivers LOVE their Leader!!! Oh how the OBAMA GIRLS Love their ENVOYS and ACADIAS! GovtMotors does NOT NEED 2 Lines of AMERICAN TAXPAYER FINANCED TRUCKS! Disgusting company. Get a REAL Truck!

DODGE! Ford, Chevrolet, Toyota or even Nissan.

@sandman4X4, Lou, Tyler, Vulpine Please get help before it's too late. Sandman: your so-called statistics about getting 10 percent increases are total rubbish, unless you replaced a totally clogged up filter with a new K&N, that is.

You and Tyler and Vulpine and Lou are all missing a key point. The resistance to the intake only becomes an issue for the engine for two critical measurements:

1. Throttle response
2. Air flow at max rpm

these are critical, just not for a pickup truck.

If you are talking about a top fuel dragster or a NASCAR motor, or a Continental aircraft engine, for example, you must have a very low restriction to the intake or you'll suffer a loss in peak power. For a dragster that means losing the race. For an aircraft engine it means the difference between clearing the treeline at the end of the runway (or not).

The difference in throttle response on a F150 or a Silverado comparing a stock OEM air filter and a K&N is un-measurable without very accurate test gear.

It makes zero difference if you're using a truck to haul the boat down the lake.

K&N makes great products and their own tests show that the biggest differences come at either full throttle or when transitioning from idle or part throttle to full throttle.

If your current OEM paper air filter is clogged, just get a new one. They're cheap and they last. After you have a few thousand miles on your K&N it flows no better than a paper filter until you service it.

Don't f**k with Superman. I know more about V8 engine technology than you guys all put together. I have built engines. I've studied and worked with this stuff since the 1960s. When you guys grow up, get back in touch.

Nobody's growing up here PapaJ. Skipping over the Manchild and political posts makes for a quick read here when I do return to catch up on the news. Don't bother screaming at me MoPaMa, I wont see it.

To add some substance:
I thought when I read the title, this was about the Easy-up Tailgate being improved. As a GMC owner, I am not impressed with the previous version, but I am rooting for this to be a useful, real world feature on all brands someday. I don't care if it makes the tailgate harder to remove. I never take mine off.

@stevador How about responding to the substance of my point instead of the way I made it.

I'm too old and too smart to be taking any advice from you about style. Tell me something smart about the science or the engineering of Otto-Cycle engines and I'll respect your point of view even if I disagree with it.

@papa jim - what is up your #ss?

I cited a test I read where they found that on a new 5.4 F150, they gained something like 3-5% improvement in MPG. I don't recall the exact number hence 3-5%. I think it was 3%. They also found intake noise was louder.

That was an actual 3rd party test not some sales brochure data.

A tonneau cover is supposed to yield similar results.

@Papa Jim: "Please get help before it's too late. Sandman: your so-called statistics about getting 10 percent increases are total rubbish, unless you replaced a totally clogged up filter with a new K&N, that is.

You and Tyler and Vulpine and Lou are all missing a key point. The resistance to the intake only becomes an issue for the engine for two critical measurements"

I would agree with you except for one specific problem: I have personally experienced both performance improvements AND gas mileage improvements by simply changing to a high-flow air filter--on multiple brand-new vehicles.

Starting with my 1996 3.8L V6 Chevy Camaro, I averaged right at 30mpg on the highway on a 750-mile road trip using the factory stock air filter. Shortly thereafter I replaced it with a K&N filter built for the stock air box and repeated the trip, averaging just over 32mpg.
In 2002 I purchased an I4 Saturn Vue and made a similar trip almost immediately after, averaging about 28.5 mpg. On replacing the stock filter with a K&N the trip averaged just shy of 31mpg. These are real-world examples.
In 2007 I purchased a 3.8 Jeep Wrangler Unlimited and guess what? I immediately took it on a 750-mile road trip--averaging just under 20mpg. Replacing the stock filter yet again with a K&N in the stock air box now as me averaging 21.5 and on some occasions (when I bother to hold my speed to 60 or less) as high as 23mpg.

Don't try to tell me it won't have any effect on everyday mileage--I know better through simple experience.

@vulpine You are a believer, so, nothing (including real world facts) will get in the way of your opinion.

Your reply did not address the key points I made about throttle response and full throttle performance. You also described what statisticians would dismiss as purely anecdotal. Your mileage may vary. Did you compare a new-in-the-box OEM filter to a K&N? You don't say.

If gauze-element filters really made dramatic improvements in fuel economy, over Stock OEM filters, don't you think the government would require every car to be equipped that way?

@papajim - sandman4x4 has never given me the impression of being an exaggerator. Motorcycles often respond to modifications better than cars/trucks. Emissions testing used to be done on bikes at a fairly narrow RPM. Bike makers would often tune the bikes to run the leanest at testing speeds. It was easy to tweak the air intake and carb settings to tune out this "flat spot".
Even more recently, offroad dirt bikes trying to meet California CARB rules would come from the factory choked off. Yamaha even went so far as to have a throttle stop in the carb that would prevent full throttle openings. Everyone would buy the bike, take it home and file off the throttle stop, remove the airbox top or snorkel, take a baffle out of the exhaust and voila, performance.
Harley Davidson tried to get a patent on the sound of their V-twins but were turned down because the only way to get that characteristic "potato.... potato" sound was to run accessory pipes. The airboxes also tended to be restrictive to meet noise rules.



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