Long post warning.
Went ahead and installed a coroplast lower grille block on the Insight. Used two zipties on either end. Size of coroplast sheet was 4" x 32" for reference. Due to 4" being slightly too tall to fit flush, there are small half-inch gaps on either side of the grille block where air can come in, but I'm fine with that.
I removed the upper grille block for now. Will reinstall it when it gets cold enough to run a full grille block.
Considering painting and gluing in a red coroplast disc over that gaping tow hook hole. Already will be getting the red paint to touch up the bumper. According to Insight Central there's a certain kind of paint (Rustoleum brand I think?) that very closely matches the Insight's Formula Red, so I'll be getting that soon. The OEM part is ~$25 to replace including shipping (
) unless my dad can get a parts discount from the Honda dealership he works at. Seems a bit much for such a tiny bit.
Brakes developed some "lot rot" from sitting for about 3 weeks, so I drove fast and used the mechanical brakes to loosen them up. They're about 80%-90% better now. Got just under 50 MPG driving like that plus almost completely depleted the battery from using it hard and doing almost no regen braking. Very inefficient driving but necessary to loosen up the brakes and get good mileage from here on out.
Had a CEL pop up - P0420, catalytic converter issue. Cleared it and it never returned despite driving about 30-40 more miles. Will see if I can take out the cat, clean it, and spray it with heatproof paint at some point.
Drove it at 80 MPH on the highway towards the end of my brake clearing run to clear up the last bits of lot rot, and was pulling 50 MPG at 80 MPH. Very impressive I'd say.
Correct me if I'm wrong, but the Insight's most efficient speed seems to be 47-52 MPH, where I can consistently get at least 105 MPG on flat, windless cruising, and 45-55 MPH where I can consistently get at least 95 MPG on flat, windless cruising. That's with the lower grille block, but missing aero panels (will be ordering Scott's belly pan).
Also got the battery charged up during the last run. As it was when driving my mom's Prius, I need to learn to trust the hybrid battery system more. It seems that the hybrid battery performs better and stays charged better when I just let it do it's thing instead of trying to maximize its efficiency. Could just be me not knowing how to do it yet though.
Upshifting at 2200-2500 RPMs seems to yield better fuel economy than taking longer to accelerate by upshifting at 1800-2100 RPMs. In other words, I got about 25 MPG higher from upshifting at 2200-2500 RPMs and driving at 50 MPH than from upshifting at 1800-2100 RPMs and driving 35-40 MPH. It's also easier to maintain a constant throttle position at 50 MPH than 40 MPH and under. Maybe I don't need cruise control.
Also added a warm air intake. Originally bought 4" dryer ducting, but it was too large (I have AC, so some of the wiring takes up some of the space in the normal WAI routing path). Bought 3" ducting and it worked fine. Had to reshape it in the area where it ran by the side of the engine, but it works. Crushed the end of the ducting against the original intake opening and secured and sealed using Tyvek tape.
The area to the upper left in that picture is one of the only slightly rusty pieces on the car. Several of the bolts are rusty, but other than that it's clean. Hoping to get some of the heatproof black paint and paint the pieces after cleaning the rust off of them sometime.
I took some black mesh and attached it to the other end of the WAI, since that opening just looked to invite debris into the intake. Used Tyvek tape again to secure the mesh along with a couple zip ties. Used a couple more zip ties to attach it to a conveniently located plastic tube of wires and pointed the end at the catalytic converter.
And the final product:
Can't say if it improved anything yet. Installed it more for faster warm up and heat retention when colder weather arrives.
More things checked off the Insight to do list. Got almost 4 more weeks to perfect this thing before returning with it to college.