In preparation for the Green Grand Prix, I installed a front belly pan on my VX this weekend. It is made out of aluminum sheet metal and a welded conduit frame. I followed pretty closely the one they made on the import tuner project sipper website.
1992 Honda Civic VX - Import Tuner Magazine
Mine has a lower front skirt though. It lowers the front bumper edge by about 3" and goes back to the firewall. I also installed another deep cycle battery to go with the alternator delete. Pics will follow and here is the testing I did.
I can't do an ABA test for obvious reasons but I did do an AB test. I don't have cruise control either so I had to hold 55mph manually. I drove at 55 on a stretch of highway that is as flat as it gets around here, which is to say that it has rolling hills. So I tested multiple times in both directions over a 2 mile stretch without the belly pan in the morning and with it in the evening, temp difference was +5 degrees in the evening.
South North
A 53 67
A 57 69
B 65 73
B 67 76
Average for the A(without mod) was 61.5mpg
Average for the B(with mod) was 70.25mpg
Northbound is a bit downhill and Southbound is a bit uphill.
Looking like a 14% increase. Part of that will be due to the temp increase, not sure how to compensate for that. It was 47 in the morning and 52 in the evening. It should also be noted that both sets show increasing numbers indicating that my transmission was probably still warming up, the engine was fully up to temp before starting both runs, but I did not drive around much after the engine got up to temp and I use a block heater also.