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Old 05-25-2011, 10:33 AM   #18 (permalink)
redyaris
Master EcoModder
 
Join Date: Jan 2010
Location: Alberta Canada
Posts: 744

redyaris - '07 Toyota Yaris
Team Toyota
90 day: 45.54 mpg (US)

Gray - '07 Suzuki GS500 F
Motorcycle
90 day: 70.4 mpg (US)

streamliner1 - '83 Honda VT500 streamliner
Motorcycle
90 day: 75.63 mpg (US)

White Whale - '12 Sprinter 2500 Cargo Van
90 day: 22.01 mpg (US)
Thanks: 81
Thanked 75 Times in 67 Posts
Quote:
Originally Posted by vtec-e View Post
Redyaris, i would like to know how you attached the undertray to the car. I was thinking of rivnuts but they entail drilling the chassis, something i am not keen on. Also, how did you finish the front end of the rear undertray, where it meets the rear axle. I see you didn't use the tow hook anchor points to fit the rear undertray as i see the tow hooks sticking out a little through the undertray. Did you simply screw it to the bumper? Mine is the mk1 yaris and the lowerpart of the bumper is metal and not straight. But it does have two m6 holes to attach the bumper.
I had an attempt at an undertray before but it didn't deliver any mpg gains. Mind you, my tanks at the time were lasting 4 weeks and the weather changes a lot here. So i wouldn't see under 5 mpg and attribute it to a mod with confidence. But i like your workmanship. More pics please!!
Where ever possible I used existing holes and did minimal drilling into the unibody frame. when I did have to drill into the frame I primed and painted the hole and then use silicon on the screw and hole to minimize rust potential. The front end of the rear undertray is attached to a bracket that is attached to some existing holes in the body at the bottom of the spare tire compartment. The back end of the rear undertray is tucked in above the leading edge of the plastic bumper on my Yaris and retained by some screws into the aluminium sheet through existing holes in the bottom of the bumper. I never bothered to test each modification I did because what I was Looking for was a trend in my fuel log. I accepted as fact all of the reading I have done on the matter of aerodynamic drag. My dream is to get into the 3.?L/100km zone some day... boat tail...
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vtec-e (05-25-2011)