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slowmover · 12-28-2010, 05:01 AM

Came across this story recently:

An Expediter and his Air tabs

" . . I had the rare opportunity to get my Sprinter into the wind tunnel at a local college to observe what happens before and after the Airtabs, as well as with and without the bug shield and rain guards. What we observed was rather dramatic.

Turns out, the bug shield and rain guard added a combined 7% increase in wind resistance, which translates to about a 3 ½% to 4% hit on fuel economy. At 22 MPG that’s about .8 MPG, which is a lot.

After a day of the students gathering the “before” data, Airtabs were mounted as close to the trailing edge of the Sprinter as you can get and still have them on a flat surface. With the Airtabs installed, the drag was dramatically reduced and showed a wind resistance reduction of more than 10%, which translates into a fuel economy savings of about 5% or 6%, which coincides with my own actual calculations.

Without the bug shield I could expect at least a 3% to 4% gain in fuel economy, so the wind tunnel math and the 2% to 4% claims made by Airtab are the same. With the Airtabs and no bug shield, I'd be getting 22-23 MPG instead of the 21-22 that I currently get. (I need to dump a couple hundred pounds of junk that have accumulated inside the van, too). . . . "

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12-28-2010, 05:01 AM	#35 (permalink)
slowmover Banned Join Date: Oct 2009 Location: Fort Worth, Texas Posts: 2,442 2004 CTD - '04 DODGE RAM 2500 SLT Team Cummins 90 day: 19.36 mpg (US) Thanks: 1,422 Thanked 737 Times in 557 Posts	Came across this story recently: An Expediter and his Air tabs " . . I had the rare opportunity to get my Sprinter into the wind tunnel at a local college to observe what happens before and after the Airtabs, as well as with and without the bug shield and rain guards. What we observed was rather dramatic. Turns out, the bug shield and rain guard added a combined 7% increase in wind resistance, which translates to about a 3 ½% to 4% hit on fuel economy. At 22 MPG that’s about .8 MPG, which is a lot. After a day of the students gathering the “before” data, Airtabs were mounted as close to the trailing edge of the Sprinter as you can get and still have them on a flat surface. With the Airtabs installed, the drag was dramatically reduced and showed a wind resistance reduction of more than 10%, which translates into a fuel economy savings of about 5% or 6%, which coincides with my own actual calculations. Without the bug shield I could expect at least a 3% to 4% gain in fuel economy, so the wind tunnel math and the 2% to 4% claims made by Airtab are the same. With the Airtabs and no bug shield, I'd be getting 22-23 MPG instead of the 21-22 that I currently get. (I need to dump a couple hundred pounds of junk that have accumulated inside the van, too). . . . " .