I have only been a member on here for a few months, but I think my project Del Sol is moving along nicely. Today I was in Lowes for a plumbing repair and I stumbled across some coroplast in the area where they sell "For Sale by Owner" signs and "Yard Sale" signs. I actually found one that was blank, 20x26" for $5.98. I cut two identical pieces mirrored around the center of my grill, spray painted them black, and attached them with zip ties and screws. Here's how it looks:
Just filled up the tank 15 miles ago, so the next fillup should tell a little about if it works or not. I didn't completely close off the grill because I don't know how the car will react yet and I am still using the a/c. I will keep my gas log updated with the progress.
last 5 fillups = 1271.4 mi 32.451 gal = 39.18mpg average
fillup after the grill block (made sure to repeat the same pump) 41.69mpg
thats a little over 6% improvement. lets see if the average stays there for the next fillup.
a side note: I don't feel that all of the benefit of my particular grill block was aerodynamic. I recently swapped out my small broken stock radiator for a larger aluminum aftermarket unit, and since then my coolant temps never got over 1/4 of the gauge even in the summer traffic. with the grill block installed, my temps get up to a little over 1/3 fairly quick and hold steady. I think this increase in underhood temp is helping my WAI and even expansion of my engine internals for a boost in apparent efficiency.
I used the OEM VX grill block for my Sol but I am thinking I am going to make one that sits flush with the bumper out of coroplast...I also made a rear bumper diffuser for the Sol, I have some more pics in my build thread...since my VSS took a crap I can't give any gains but the car felt more stable on the highway...