the MCA S13 nissan Time Attack car is one of the wildest designs that still looks like a normal car that as been modified:
look at that diffuser!
this car was extremely competitive in 2012-14, taking some of the fastest laps for a RWD and overall time attack cars.
here is a build article showing some of the construction:
Nerd's Eye View: The MCA Suspensions "Hammerhead" Silvia S13
there is no reason why much of this sort of construction couldn't be replicated with low cost materials, but aimed at ECO rather than Downforce
V2 looks like this:
the NEMO evo is one of the fastest as well.
in 2012 I think(?) the MCA s13 only had about 500 horsepower to the wheels. a far cry from some of the monsters that are out now with 800-1000+ and All Wheel Drive like the NEMO evo.
only about 8 ago the cyber evo was nearly unstoppable and considered insanely crazy:
speedhunters referred to this as extensive bodywork and huge lips and canards hah!
little did they know that people were going to create low flying bi-planes with 4 wheel drive in the near future.
Time attack racing is crazy, and it shows us a lot about how crazy we can go in the search of specific goals. Many of us don't have the tools or money to build crazy stuff. But I hope that we do try to think hard and be bold in our quest to achieve better efficiency in our cars because it does make a difference.
Talk to your friends and neighbors about your projects, share and spread the word. Many of the mods you do are easy and simple and the gains are easy to see.