Skid plate/belly pan

[Billett]

Fitz, I've seen those grille covers before and because they are more for aesthetics like you said, I wanted to try something a little different. Not to mention that's quite a bit of cash for a piece of sheet metal with one bend...

[Fitz]

Originally Posted by Keith Seymore

This might be of some interest:

http://media.gm.com/content/media/us...ckup-aero.html

(I worked with Diane Bloch extensively in the past; Nina Tortosa was credited with most of the work on the Volt program).

K

What the article says about the 2014 sierra is most certainly true in as far as it goes. It also points out the problems with making generalizations about scientific measurement. On that truck the cab roof was lowered, the bedside height was raised 4 inches, the gap between the cab and bed on that truck was reduced from 2 inches to less than 1/2 inch. These things all change the flow of air over the back of the cab and at some speed, the "bubble" behind the cab of this truck extends past the tailgate making the tailgate down position worse than tailgate up. What the article does not say is below that speed, the bubble formed is shorter than the bed length and turbulent flow off the truck roof strikes the tailgate and builds a high pressure area there contributing to increased drag just as it does in the older design and their conclusion about gate up/gate down and bed covers present or absent are no longer valid.

Our 67-72 trucks, as I have said before, have the aero design of a brick; which makes their behavior at low and high speeds quite different but there are two phenomena that remain unchanged:
1. Drag is dominated by frontal cross-sectional area
2. At some speed that I do not now know, the turbulent flow bubble is shorter than bed length making the tailgate a significant contributor to drag for both trucks. At some higher speed that region to grows beyond the length of the bed the tailgate is no longer a contributor to drag for both trucks. That speed is also different for both trucks.

So, back to determining if a belly pan makes a measurable improvement in fuel economy. The answer you get in field testing will differ depending on the speed you choose to run. To get a valid and repeatable result that focuses on Belly pan or no belly pan effects requires a means of testing that avoids the changing influences of the tailgate. The only way to do that is cover the bed. Doing so might increase the drag or decrease the drag but that drag will at least be related to speed by a smooth square law characteristic without the discontinuity caused by flow transition beyond the length of the bed.

[Billett]

Well thankfully I've already got a bed cover.



I live in south jersey, but drive to Philly everyday for work. It's about a 100 mile round trip, and I would say a solid 75 miles is highway. I plan on filling the tank myself to avoid variation there, drive to work, drive back, fill it up again and record mileage.

[Keith Seymore]

Saw this in the GM Tech Center news today; leaving it here in case there is anything of interest -

2014 Chevrolet Camaro Z/28 is Designed for Downforce

Racing-inspired design elements enhance high-speed stability for faster laps

11/26/2013

DETROIT – When it comes to keeping its tail on the track, the 2014 Camaro Z/28 manages airflow like few other production vehicles, generating downforce like a race car to press the tires against the track for high-speed stability and greater cornering capability.

Numerous modifications were made to the exterior, compared to the Camaro SS, with new and revised content developed to improve aerodynamics, powertrain cooling and brake-system cooling. They help the Z/28 produce 440 pounds more downforce at 150 mph, relative to the SS, which generates slight lift at that speed.

In fact, the aerodynamically optimized design helped the Camaro Z/28 log a lap on Germany’s legendary Nürburgring road course that was four seconds faster than the Camaro ZL1’s, and beat published times for the Porsche 911 Carrera S and the Lamborghini Murcielago LP640.

“Most production cars are designed with some lift at speed in order to slip through the air for greater fuel economy, but the all-new Camaro Z/28’s track-oriented purpose dictated an entirely different take on airflow management,” said Tom Froling, lead development engineer – aerodynamics. “Its carefully tailored aerodynamics package generates downforce for greater handling stability at speed, and the grilles are optimized to meet stringent cooling flow and brake-cooling requirements.”

The new Camaro Z/28 is the fastest factory-produced Camaro ever on a track, with improved speed coming from three areas:

• Increased grip: The Z/28 is capable of 1.08 g in cornering acceleration, due to comprehensive chassis revisions
• Increased stopping power: The Z/28 features Brembo carbon ceramic brakes capable of 1.5 g in deceleration, and consistent brake feel, lap after lap
• Reduced curb weight: The naturally aspirated Z/28 weighs 300 pounds less than the supercharged Camaro ZL1, with changes ranging from lightweight wheels to thinner rear-window glass.

Power comes from the 7.0L LS7 engine, rated at an SAE-certified 505 horsepower (376 kW) and 481 lb-ft of torque (652 Nm). A close-ratio six-speed manual transmission is the only transmission offered and power is distributed to the rear wheels via a limited-slip differential featuring a helical gear set, rather than traditional clutch packs, for optimal traction.

“It’s a track-proven, uncompromising collection of hardware that generates the Z/28’s power and channels it to the ground, but it’s the way the Z/28 manages airflow that truly helps it stick to the track to make it fast and stable at speed,” said Froling. “None of the car’s unique exterior elements is without a performance-enhancing purpose. In fact, it shares several racing-inspired aero features from various Camaro and Corvette race cars.”

Computational fluid dynamics, reduced-scale rolling wind-tunnel testing, full-scale clay models and full-size prototypes were tested in several wind tunnels, including General Motors’ wind tunnel in Warren, Mich., resulting in five primary contributors to the Z/28’s aero supremacy:
1. Front splitter
The Z/28’s front splitter is a large aero panel that provides downforce at the front of the car, enhancing cornering capability and high-speed stability. It is designed to withstand 250 pounds of downforce at its tip and is matched with an aero closeout panel under the front of the engine compartment that also enhances aero characteristics – along with molded-in aero features forward of the front wheels.
2. Rear spoiler with ‘wickerbill’
At the outset of development, the aerodynamic coefficient of drag goal was achieved with original Camaro SS content and an accessory rear spoiler, but to meet the downforce requirements for Z/28, the rear spoiler was modified with a “wickerbill” – a small, vertical tab at the edge of the spoiler. Although an aesthetically minor change, it adds approximately 28 counts of drag, improving rear lift performance by 70 counts. That allows the Z/28 to handle turns at higher speeds and delivers greater overall high-speed stability.
3. Hood extractor vent
A functional carbon fiber hood extractor provides increased engine cooling by allowing hot air an exit route, but also plays an important in the car’s aero performance. It provides a path for air channeled through the grille to exit out the hood and over the car. Without the vent, the air would be pushed out the bottom of the engine compartment, which could generate lift. The design is similar to the extractor featured on the Camaro ZL1.
4. Rockers, wheel house extensions and front tire deflectors
Specific rocker moldings provide aggressive styling and improved aerodynamic performance, while unique wheel house extensions cover the Z/28’s wide tires to push air past the tires. Deflectors at the bottom-front corners of the front wheel flares also contribute to the car’s downforce-producing aerodynamics, taking the place of a conventional air dam.
5. Belly pan
The Z/28 underbody incorporates a belly pan that helps reduce front lift. It was developed using computational fluid dynamics and wind-tunnel testing. Along with the aero benefit, it also contributes to drivetrain cooling, with modified NACA duct profiles designed to draw air into the underbody tunnel area, where the highly energized air provides extra cooling for underbody components affected by the exhaust thermal energy of the LS7 engine. Unique wheelhouse liners with closeouts work with the vehicle underbody for optimal airflow, too.

Additionally, the Z/28’s unique front fascia plays an important role in airflow management. It is based on the Camaro SS, but the fog lamps, air dam and the upper-base grille are replaced with covers for deleted fog lamps (to reduce weight), an air duct support bracket, an airflow-optimized upper grille for enhanced cooling and a modified fascia lower inlet that incorporates provisions for the brake cooling ducts. They funnel air from the splitter/lower grille through the ducts to the brake rotors and calipers.

The 2014 Camaro Z/28 arrives in dealerships next spring, ready for the 2014 racing season.

[In The Ten Ring]

Originally Posted by Keith Seymore

Given the benefit of further thought: you want the biggest bang for your buck?

Slow the H.E.L.L down!

(lol)

The aerodynamic drag increases with the square of the speed.

No other physical dimension or attribute has that much power by comparison.

K

Slowing down works so well, I don't understand why more people refuse to do it.

In 2006, I was driving back to WV from Mt. Airy, NC, and I decided to see if dropping from my normal 70 mph to 55 mph would have much effect.

In that 2003, 4 banger Honda Civic (gasoline engine, automatic), if I did 70 mph on the interstate I saw 38 miles per gallon. When I began to drive 55 mph, I SAW 50 MPG. After I had the factory spoiler attached (looked killer!), my mpg dropped and stayed at 46 to 48.

In my current "lead sled," 2002 Honda Accord, 4 banger auto, if I do my standard 55 mph on the interstate, I see 34 mpg. Speeding up to 70 mph drops that to 24 mpg. Now a lot of people simply say, "I can't drive that slow" but I feel they are very immature. The fuel savings will add up and I have to tell you, it's much more relaxing to drive 55. There is more reaction time, much more. I'd like to see a return to the 70's and 80's national speed limit of 55 mph.

[BrianG]

I wouldn't say immature, but instead intelligent. Driving 55mph is dangerous when most everyone else is going 70mph. I helped my brother move back to Michigan from Kentucky this spring. My dad was in front of me hauling the UHaul trailer. We didn't have it loaded as best as it should have been and about 55 was all we could do. I was in my brother's Impalla taking up the rear. I HATED it. Not that it was too slow, but watching those big trucks come up in the rear view mirror was horrifying. Can you say pucker facter!!!

The fuel savings may not outweight the risk of getting run over, and those numbers may work out for a small Honda but not every vehicle. My Envoy seems to do best at around 65 or so, although I usually just stick with the flow of traffic. I feel it is the safest way to drive. I'd rather get there in one piece then worry about saving a few bucks.

[Spartan]

I don't know much about aerodynamics but I can hit a golf ball pretty far. Dimples gotta be for a better reason than just making me feel like I'm killing it.
Didn't Mercedes make a dImpled car?
Cheers!

[JointTech]

I think the dimples are for stability not distance.

[Spartan]

Originally Posted by JointTech

I think the dimples are for stability not distance.

Ahhh... so I AM killing it! lol

So would dimples help bellypan stability? I'm only kinda serious since I really don't have a clue or really care... I mean my Honda fit is pretty much shaped like a tear drop and gets incredible mileage.

I could swear Mercedes made a car with dimples so it would slip through the air...

Another suggestion I would have would be to chop it and angle the windshield back further... Thats what they did to jeeps. Just look at the cherokee and see what they did to the brick to make it resist a little less.

[69CSTranger]

Interesting conversation. I'm interested in improving the aerodynamics for high speed stability and cornering, which seems to be:

Lower truck as much as possible with increased rake
Install front air dam
Belly pan.
Rear Diffuser
Soft bed cover
Rear spoiler/wing

Shave door handles/mirrors
Chop top.

I personally think its great to look to look for aerodynamic advantages with our trucks. Every little bit helps.

[seattle gmc]

Originally Posted by Spartan

Ahhh... so I AM killing it! lol

So would dimples help bellypan stability? I'm only kinda serious since I really don't have a clue or really care... I mean my Honda fit is pretty much shaped like a tear drop and gets incredible mileage.

I could swear Mercedes made a car with dimples so it would slip through the air...

Another suggestion I would have would be to chop it and angle the windshield back further... Thats what they did to jeeps. Just look at the cherokee and see what they did to the brick to make it resist a little less.

I think the the mythbusters created a dimpled to car test some mpg claims, cant remeber if it worked or not.

[69CSTranger]

Another possible addition would be vortex generators. I'm in aviation and aircraft use these all the time to reduce drag. Not sure how well they would work on our truck but it seems like the cab would be a good place to start.

http://www.airtab.com/gallery/jetcar.html

[Billett]

Haven't done anything besides get a few baselines for mpg. So far it looks to be right around 14 mpg, but that seems a bit low to me. Fairly consistent though so I guess I'll take it. Although I'm not doing anything to the truck besides drive it until it gets a little warmer out haha. Once it warms up I'll actually start recording some temperatures and mileage and really go from there