Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - A failed modification (partial rear undertray)

pjbgravely · 03-29-2012, 10:45 AM

A few years ago I did a mod to keep dirt and salt from getting kicked up on top of my gas tank from the rear wheels. I wondered why they left this open at the factory. I found out, I lost 5 MPG closing off the rear fender wheels at the back. The pumping action of the tires makes the fender wells a high pressure area.

When I put in my rear bumper mod (mine has to cover the gas tank) I left a tunnel on both sides to let the wheel wells vent. I saw a slight increase, and dirt doesn't pile up on the gas tank.

This summer I will try to dial in the rear angle by raising or lowering the rear springs.

03-29-2012, 10:45 AM	#6 (permalink)
pjbgravely EcoModding Lurker Join Date: May 2011 Location: Sidney NY USA Posts: 64 Horse with no name - '00 Ford Mustang Base Team Mustang 90 day: 20.53 mpg (US) Orange peel - '00 Ford Focus SE 90 day: 26.83 mpg (US) Thanks: 3 Thanked 11 Times in 7 Posts	A few years ago I did a mod to keep dirt and salt from getting kicked up on top of my gas tank from the rear wheels. I wondered why they left this open at the factory. I found out, I lost 5 MPG closing off the rear fender wheels at the back. The pumping action of the tires makes the fender wells a high pressure area. When I put in my rear bumper mod (mine has to cover the gas tank) I left a tunnel on both sides to let the wheel wells vent. I saw a slight increase, and dirt doesn't pile up on the gas tank. This summer I will try to dial in the rear angle by raising or lowering the rear springs. Last edited by pjbgravely; 03-29-2012 at 11:09 AM..