Giving the New Beetle Wings
By Bill Moore
This week the EPA came out with its annual rankings of the best and the worst fuel efficient cars and trucks in America. As you might expect, the Honda Insight and Toyota Prius were at the top, but next came Volkswagen's New Beetle, the diesel version with a manual transmission officially rated at 37 city/44 highway, along with the Golf model.
This should help bolster flagging sales for the German company whose origins go back to the Hitler-era and engineering genius of Ferdinand Porsche.
Now another engineer/scientist -- this one retired from the American aerospace industry -- by the name of Ernie Rogers has taken it upon himself to improve the venerable "Beetle" by giving it 'wings'.
Seeing the handwriting on the wall earlier than most, Rogers bought a 2003 VW TDI New Beetle with the specific goal in mind of taking advantage of its fuel-efficient diesel engine. But he also knew that the retro-designed Beetle had a serious design flaw, one that he figured could be fairly easily and cheaply fixed. All the car needed was wings... well, actually a (one) wing mounted on the slopping rear deck of the arch-shaped car.
Besides working for Thiokol, the folks who make the solid rocket motors for the Space Shuttle, Rogers also designed wind turbine blades and it was that experience that got him to thinking about improving the aerodynamics of the New Beetle.
Arches Are Strong, But Not Aerodynamic
Now you would think that the distinctive curved profile of the reincarnated "Bug" would be one of the most efficient, low-drag designs around, but it's not, according to the Utah rocket scientist.
"The Beetle is just a really unfortunate shape in terms of its aerodynamics", he asserts.
What happens, he explained to me, is the air flowing over the top of the car responds much as it does on an aircraft wing, creating negative air pressure that on a plane translates into lift but on the Beetle creates a eddy of performance-robbing drag just above and behind the car.
He told me that the Beetle is a very special case, unlike most other cars where millions of dollars are spent on wind tunnel testing to help smooth the flow of the air up and over the car. He asserted that the trunk (boot) on most modern cars are carefully sculpted to help channel air flow so as not to create the same type of eddy found on the Beetle.
"The drag of a Beetle as it comes from the factory is 0.38. After I got done, it's something less than 0.30. A little better maybe than the Jetta".
Rogers' Beetle is a 2003 model year. It came standard with a 1.9 liter turbocharged diesel engine that produced 90 horsepower at just 3,750 RPM and a powerful 155lb-ft of torque at a mere 1,900 RPM. The newer model years had their engines up-rated to 100 hp, promising 38 mpg city and 46 mpg on the highway. But it's Rogers' opinion that the earlier version of the 1.9 liter is more fuel thrifty.
He knew when he bought the car that while it's engine was one of the most energy efficient available anywhere in the world, it's aerodynamics needed refining. That's where his home-made "wing" came in.
"Adding [the] wing on the back corrects the design fault", he told EV World.
With or without Rogers' wing, the TDI has suddenly become very popular of late because of its excellent fuel economy. Anecdotally, he said that a dealership in Michigan is purported to have stockpiled some 100 TDIs for a special event, only have them almost immediately sold out as fuel prices skyrocketed. He has also heard that dealerships in California have agents scouring other states looking for used diesels for their customers.
Besides adding the rear spoiler/wing, Rogers has implemented other modifications, though none as unusual as the wing. He's replaced the stock tread with larger diameter, low-rolling resistance tires and switched to synthetic lubricants.
Before modifying the car, he determined from his own tests that on the highway at a steady 65 mph, the car would get about 52 mpg (4.5L/100km), three miles better than what the window stick said. What he also discovered in his testing on a stretch of straight level highway west of the Great Salt Lake, is that for every 5 mph you reduce your speed, you gain a 10 percent improvement in fuel economy.
"If you speed up, you'll lose ten percent". He explained that its also additive. If you slow down by 10 mph, your fuel economy will improve by 20 percent. The rule, he said, works between 60 and 80 mph.
After adding the wing, he saw the car's fuel economy improve to 58 mpg (4.0L/100km). With the addition of the low-rolling resistance tires and low-friction lubricant, this improved to 65 mpg (3.6L/100km) in the summer at a steady 65 mph.
Roger's drove the car back to a VW TDI convention in Wisconsin this summer, traveling along busy I-80, which goes right through Omaha where EV World is located, at a steady 55 mph. Just as his fuel economy vs. miles per hour rule suggested, he got a remarkable 78 mpg (3.0L/100km)… on B5 biodiesel, a blend of 95% petroleum diesel and 5% biodiesel. While he admits you have to be a bit crazy to drive that slow on an Interstate where semis and SUV come roaring around you at 80 mph or faster (the legal speed limit is 70 mph), he only got honked at twice.
The wing itself is of very simple construction: foam, plywood, paper mache and fiberglass. It's attached to the car by special brackets designed and fabricated by his son so as to not mar the exterior of the car. The trunk (boot) of the car is still accessible.
He pointed out that there is nothing overly sophisticated in the design of the wing or its airfoil, saying a flat piece of board would be 99% as effective. He is also not a big fan of "racing" spoilers some people put on their trunk decks since they really do little to enhance the efficiency of the car and, in fact, can increase the car's drag.
"If they are designed correctly, they will get the down force without creating any additional drag, or may actually get a reduction in drag like I did".
He commented that his wing performs essentially the same role as the truck of a modern car, helping to reduce build up of the negative pressure flowing over the top of the vehicle.
"The (VW) Jetta has a drag (co-efficient) of 0.30 compared to the 0.38 of the Beetle.
I asked Rogers how the wing influenced the handling of the car. He replied that it improved it by increasing the loading on the rear wheels, which are under-loaded on the conventional, front-engine powered New Beetle. (The original VW Beetle had its engine in the rear of the car). The additional negative air pressure on the unmodified version only aggravates this, he stated.
"I've made the car safer by cleaning that up. The factory should be copying me", he said with tongue-in-check. "So far they're not".
Building a similar wing for the family SUV would do nothing to improve its fuel economy, he agreed, but slowing down and using low-fiction synthetic oil will help, regardless of the size of the vehicle. Low rolling resistance tires could, however, be problematic for an SUV, so proceed cautiously here. Rogers suggests seeing what manufacturers are using on their newest vehicles, which are likely to offer the lowest rolling resistance for that class of vehicle. He warns though, that your local auto retailer is not likely to be the best source of information on this issue. He recommended checking out the reviews done periodically by Consumer Reports magazine.
Despite the obvious advantage of adding the wing to the rear of the car, Rogers has had little luck getting commercial automotive spoiler manufacturers to take any serious interest in the idea. He's talk to some dozen companies who have shown no interest, whatsoever. He told EV World that he'd be happy to turn over the concept to anyone interested in commercializing it since he's got other projects that he wants to pursue.
Roger's didn't know, off-hand, how many New Beetles have been sold to date, but the year VW introduced the car with the 1998 model year, it sold 55,842 units in North America, 83,434 worldwide. Sales have steadily slumped since then. The company sold just over 42,000 in 2004.
Now that he's proven to his satisfaction the merits of giving the New Beetle a wing, he's moving on to a new project: a completely clean diesel engine.
"The diesel engine is inherently far superior to the gasoline engine in terms of the amount of fuel that doesn't get burned. Diesels burn very, very cleanly. Unfortunately, the small amount that doesn't burn stinks terribly.
"So, I've gone back to the basic theory of operation of the engine and found ways to revise it to make it make it a virtually non-polluting engine".
On the topic of biodiesel, Rogers is very much a proponent of renewable fuels. He explained that because the energy content of petroleum diesel is higher than biodiesel, he chose to use B5 on his trip to Wisconsin to get the improved lubication from biodiesel, but the greater fuel economy from diesel.
"The wonderful thing about a diesel is that it will burn almost anything you put in it".
Be sure to listen to the complete interview in MP3 format.