After 250+ posts, I think it's time to let my "3rd Gen Prius Aeromodding" thread rest. I thought I would start a catch-all thread not just for my car, but anyone else who has competed or plans to compete in the Green Grand Prix and wants a place to discuss modifications specifically for that and other fuel economy events.
The reason I'm starting a new thread for this: One thing I was not prepared for was the amount of elevation change in the Watkins Glen short course profile, something I had not researched before the GGP.
From Turn Two through the back straight, the course rises 124' at an average grade of nearly 2.5%, although it is steeper through Turns 3 and 4 than on the straight itself. Laboring the car up that grade every lap, I got to thinking--a significant aeromod (like the cargo box tail), which adds a fair amount of mass to the car, doesn't really pay for itself in an event where I have to maintain an average speed of 45mph and am speed-limited to 60mph; in other words, having more momentum or improved aerodynamic efficiency on the front straight doesn't pay off as much as it could since I can only take advantage of that up to a certain speed, for which I'm penalized anyway if I go too fast and overshoot that 45mph average. Also, while slowing down on the uphill is an option, there is a minimum 35mph speed requirement for the event. So, I can't crawl up the grade to minimize the impact of having to carry all that weight up, and I can't coast past 60mph on the front straight to recoup some of that energy expenditure by taking advantage of the increased momentum.
So, I'm re-thinking my approach for the GGP. In the next few days here, I'll be removing the tail, cargo carrier, and hitch receiver assembly (which together weigh nearly 150 lbs), and starting to gut the car to get rid of as much mass as possible. I plan on a new tail design, with light weight as a design goal; most of the aeromods on the car will stay in place (since most of them don't weigh much). Even without the tail, the Prius is sitting at Cd .21, so it's not like I'm giving up something major in that area. This is a new direction for the car; I dabbled with removing some weight a few years ago, but was never very serious about it and ended up adding a lot in the tail, sound insulation and, for a while, a big subwoofer box. I'll now be focusing more on mass reduction than new aerodynamic devices, hence this new thread, in Ecomodding Central rather than Aerodynamics.
I'm not entirely crazy, as most of my driving these days is in-town and low-speed, grocery store runs and the like. So, a drastic reduction in mass should benefit me more than it would have 4 years ago, when I was doing mostly highway miles. This is very experimental--I'm not sure what it will be like to live with a daily driver with no sound insulation, gutted interior, etc. But I'll find out! And I guess I'll find out how far I'm willing to go in the name of science, and how long before my partner refuses to ride in my car.
As of now, here's what I have taken out:
-Hatch panels: 5.2 lbs (21.6 lbs with added insulation)
-Rear door panels: 10.6 lbs (20.0 lbs with added insulation)
-Hatch door panels: 5.4 lbs (10.4 lbs with added insulation)
-Wheel covers/pizza pans: 2.5 lbs (9.4 lbs with pizza pans)
-Front swaybar and endlinks: 8.4 lbs
-Trunk mat: 5.4 lbs
-Rear speakers, miscellaneous hardware: 5.3 lbs
-External mirrors: 4.2 lbs
-Tonneau cover: 4.2 lbs
-A-pillar trim and dash speaker grills: 3.0 lbs (4.2 lbs with added insulation)
-Passenger wiper: 2.8 lbs
-Rear wiper and motor: 2.4 lbs
-Intake resonator: 2.0 lbs
-Hood insulation: 1.2 lbs
-Plastic engine cover: 1.0 lb
For a total of 102.5 lbs gone, or 63.6 lbs from OEM curb weight, and I haven't even gotten to the tail/hitch receiver or spare tire. I'll update this list as I take things out and see if I can get some pictures as I go along. I also plan on weighing the car at a truck scale later this summer (we have a CAT scale at the stop just outside town) to get an accurate weight.
Some things I've thought through already--I'll be removing the headliner and sun visors, so I've ordered a vinyl strip to go across the top of my windshield (because racecar). The pizza pan wheel covers will be replaced by light plastic or acrylic annular discs, so I have access to the lug nuts without removing them (I found this was a pain with the full covers). All safety equipment will remain in place--I won't be taking out airbags, drilling holes in bumpers, removing crash bars in the doors or anything like that. The only rule for the modified class at the GGP is that the vehicle must be street legal, so anything that violates that criterion is out.
Other than that, game on.