I've been lurking here on ecomodder for several months now, reading up on HFE driving techniques and aero mods, I'll begin with a brief introduction: I started hypermiling about a year ago when I was delivering pizzas, and got myself up to about 43 MPG combined driving slow and coasting. Since then I switched jobs, logging most of my miles on a 10-mile city commute. I've been getting about 39 MPG with 80-85% city miles, mostly in heavier traffic. I'm still trying to learn how to tweak P&G for my car and driving conditions, but that's another subforum. However, once or twice a month I make a 240-mile round trip on I-5 during off hours, which is perfect for working on hwy FE and aero mods.
My 1st mod, which I don't have pictures of, was installing some front tire deflectors like those seen on most new cars--just a flat piece of plastic placed to cover the inner half of the tire profile and a few inches inboard of that. Based on observation and reading, it seems that this is usually the optimum placement as much of the drag in this area comes from the wheel wells and their interaction with the inner sides of the spinning tires. I didn't get any solid comparison testing with this mod.
My 2nd mod was a grille block:
The radiator is tiny, and covers only the passenger side of the grill opening, so the grill block leaves about 30% exposed. I have not measured any significant improvement with this, which is frustrating and confusing, especially since the whole driver's half of the grill was just letting air straight into the engine bay where it slowed down and exited underneath. I know my temps are fine and the fan almost never comes on. Eventually I will optimize this mod by moving the opening to the center of the radiator area and sealing the zone between the grill opening and the radiator face.
My 3rd mod was an front undertray made of coroplast:
The stock front underbody was very uneven, but I finally managed to get a smooth shape and screw it down. I haven't really tested this mod on its own, but in my judgment the airflow will have to be smoothed farther back and the engine bay venting will have to be optimized in order for this mod to reap any overall drag reduction benefits.
I've recently tweaked the undertray, adding some coverage to the wheel wells and adding pieces further back:
I'm not really happy with how it turned out, as there is just too much void aft of the front undertray piece, especially in the middle exhaust tunnel. I was going conservative because I wanted to make sure there was enough opening to extract the air going through the radiator. I've actually already got a coroplast piece measured and cut for replacing the section from the front wheels to the rear of the engine bay, but I didn't have enough time to install it.
Along with the undertray revision I made these larger curved front tire deflectors:
Sorry for the blurry pics, daylight was gone. I need to reshape these to cover more of the wheel well opening, and to extend the aft edge farther back closer to the front tire.
Up next will be the revised tire deflectors, extended undertray, and rear undertray.
So, comments, suggestions, comparisons?