by Robert Patton, Editor TDR
ADDITIONAL FUEL ECONOMY TIPS
As an enthusiast group the TDR members are well aware of the tried-and-true tips for better fuel economy. In this issue we can add to our collection the fuel economy insights from an Automotive News report and from TDR writer John Martin. First up, text from Automotive News.
No doubt the automotive engineers have devoted many resources to gain a competitive advantage in the quest for greater miles-pergallon. In the 9/22/08 issue of Automotive News, there was an article with General Motors’ design Vice President Ed Welburn that discussed fuel economy titled, “It is Difficult to Design Fuel Efficiency into Big Pickups.” Selected text follows:
"When we looked at very aero trucks that sat lower, customers were not interested in them,’ says Ed Welburn, General Motors’ design vice president. ‘They just weren’t."
"A pickup’s V-8 engine, tall silhouette, and heavy-duty components and mass eat away at fuel economy. Another culprit is the open cargo box, an aerodynamics nightmare when the pickup is rolling at highway speed."
"The air comes over the cab and loses its attachment,’ Welburn says. ‘I’m thinking about some of the computer images I have seen of airflow over a cab. It gets into that box, and it just tumbles wildly, it just rolls, creating a drag that hurts fuel economy."
What causes that problem?
"It’s the shape of the rear glass, Welburn says. It is the shape of the upper portion of the cab. It is a real challenge. The cab is just chopped off. Once the air gets past there, it just goes crazy."
"The key, Welburn says, is developing design techniques to keep the air attached."
"How do you keep that air attached? It is all about aero."
"Part of the solution might be vortex generators — essentially, aerodynamic shapes that could be molded into the roof or body panels. That technique is used on airplane wings."
"They are just there to just clean up the air, to get the air to flow, Welburn says."
“Studies of aerodynamics have struck down a popular belief about pickups: A lowered tailgate results in better fuel economy."
"It doesn’t. It is better when the gate is up. That trailing edge helps to some degree."
"A covered cargo box does provide better airflow, But, Welburn says, ‘The question is, with a closed box, what height works best — and it
depends on the shape of the cab, the tail of the vehicle, things that happen forward of the cab."
"A covered pickup box is one of numerous modifications GM made to boost fuel economy on two models introduced for 2009. The two wheel-
drive trucks — the 2009 Chevrolet Silverado XFE and GMC Sierra SFE — are both equipped with a 5.3-liter V-8 and six-speed automatic transmission."
“The result: 15 mpg city and 21 highway. Non-SFE models get 14 mpg city and 20 highway."
Among the changes to create the SFE models:
• Vehicle height was lowered 18 millimeters.
• A soft tonneau cover was placed over the cargo box.
• The front lower air dam was extended 10 millimeters.
• Low-rolling-resistance tires were added.
• Narrower tires were used.
• Vehicle weight was reduced by about 150 pounds.
"Considering the degree of modifications, the small bump in mpg might be interpreted as minuscule."
"Welburn’s response: ‘One-mile per gallon is a big deal in this company."
"In the future, pickups may feature aerodynamic techniques once considered unthinkable."
"But compared with the cost of other technology to improve fuel economy, now all of a sudden, things like an adjustable air dam or adjustable wing—well, maybe they aren’t so expensive after all."
Next up is text from TDR oil guru (Issue’s 54 was the start of his correspondence), John Martin.
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