Autoblog

At highway speeds, your vehicle is fighting an invisible foe trying to hold it back. The nemesis is wind resistance, and it is an automobile's worst enemy. Overcoming the resistance of the air is the key to increasing acceleration, top speed, and improving fuel economy.

Wind resistance is often measured with sophisticated computers in multi-million dollar wind tunnels. The result is usually expressed as a number called the "drag coefficient" (Cd). While having a low drag coefficient is important, the size of the vehicle (expressed as "frontal area") is also important. In general, as drag coefficient and frontal areas decrease, a vehicle becomes easier to push through the wind. Automakers are well aware of this, so they go to great lengths to ensure a low Cd on vehicles designed for high efficiency. Some approximate Cd values for well-known vehicles.

• .25 Honda Insight
• .26 Toyota Prius
• .27 Nissan GT-R
• .34 GMC Acadia
• .36 Bugatti Veyron (spoiler retracted)
• .36 Chevrolet Suburban
• .48 Classic VW Beetle
• .65 Tractor Trailer (with fairings)
• .75 Formula 1 Car (downforce = high drag)

There are a couple of ways to determine the Cd of your vehicle. If your vehicle is stock, simply look it up on the Internet. If you have modified your car with wider tires, spoilers, roof rack, or changed the ride height, then your Cd has changed. To determine whether your mods are hurting or helping you at the pump (or the track), why not calculate it yourself with a few household items and an Excel spreadsheet? Of course, this requires a bit more effort... but, if you have any geek in your bloodstream, this will really get your juices flowing. The process is too long to detail here, but check out the simple instructions, grab your household items, and let us know what your results are. Thanks for the tip, Farris!

[Source: Instructables]

Arden, the German tuning firm that's been tweaking Jaguars for decades, is teasing us with this concept shot of its new Jaguar XF AJ 21. We just drove the 2009 Jaguar XF and felt the sheetmetal was lacking some excitement. In a good manner, it appears that Adren has addressed some of our concerns with its aerodynamic sport package including new front and rear bumpers, new side skirts, and a more aggressive wheel package. Look closely and you'll notice the cat is back on the hood (maybe too much redundancy, considering the badge is just below it as well?). Expect more photographs, specifications and pricing in the near future.

[Source: CoolBrit]

Some thought it was tasteful, some thought it was bland. One way or another, the 456 GT was a refreshingly understated touring machine from Maranello when its contemporaries were dominated by enormous ducts and wings. Compared to its successor, the 612 Scaglietti, the 456 was an exercise in good proportions and tasteful lines. Then some nutcase went and ruined it.

Like drawing a moustache on the Mona Lisa, this GT had an oversized rear wing grafted onto its boot-lid. The flip-up headlights – the last of its kind for Ferrari – were replaced with clear lenses mimicking the 550 Maranello. And the elegant five-spoke wheels were swapped out for multi-spoke racing rims.

It's bad enough when some tuning house rips up an F430 or 575 and mods it beyond recognition, but this example makes us wish Ferrari retained the right to repossess any of its creations that are being mistreated. Where's the SPCF when you need them?

[Source: Carscoop]

JE Design has gone and messed with the Audi TT. The changes are subtle, which is good, because it's hard to improve upon the TT's form. The JE kit will surely draw mixed reviews, though we like that their kit still lets what's good about the car shine. There's new pieces for the chin spoiler in front, adding strange little vents at the leading edge of the wheel opening. We can't imagine that they actually serve any purpose – perhaps they vent heat from the foglamps? We're sure that's a common problem. The requisite overly-large, overly-low-profile tires are there, but the benefit of the bigger rolling stock is left unrealized. We see puny (puny's such a relative term) brakes hiding out behind the wheels. The only functional point behind ultra-low profile rubber and rims beyond 17" is to fit as much brake rotor diameter as possible under there, and what we're seeing is plenty of extra clearance around everything. And apparently twin exhaust outlets do not a fast car make; they've been superceded by quad tips. The smooth rear decklid has had a lip spoiler applied to add some downforce. What the spoiler really does is add a pimple to the ass of an otherwise smooth form. The stock pop-up spoiler gets in the game to add downforce, and when it's retracted, you're not going fast enough to need any extra drag. It'll look real racy in traffic at an average speed of 15mph, though.

[Source: JE Design]