The MPG improvements on my Civic hatch were so impressive that I did the same treatment to me wife 02 Honda Odyssey minivan. I installed underbody panelling and a 50% grill block. It was getting 24MPG in local driving and about 20MPG on the interstate (low 70's MPH). After the mod, my wife said she got 24MPG after a 75-80 MPH run down the interstate.
I haven't been able to log onto this board since it went to the new layout from my home computer, so I am having to do this from work. The board shows when my last visit was and shows me on the list of members currently online, but it won't let me log on. When I try to log on, it keeps kicking me back to the log on screen.
The Odyssey didn't have any underbody panelling, but did have some plastic fairings under the front of the engine. I haven't done any controlled testing yet. When working under the Odyssey, it was obvious that different committees with different priorities designed different parts of the underside. The aerodynamics of the engine compartment was done fairly well, with wheel spoilers in front of the front wheel housings that had slots on their backsides that exhausted air from the intake air cooler (left side) or from the radiator (right side). Most of the radiator air was exhausted under the car in the traditional fashion. But further back on the underside there was a lot of hardware hanging out in the wind. I blocked off the intake to the intake air cooler and rerouted the radiator exhaust out to the front wheel wells through the drive train openings on the sides of the engine compartment like I did on my Civic. I suspect the front tire is acting somewhat like a squirrel cage blower to help suck the air out of the engine compartment.
Basjoos, you have almost identical vehicles as I. I have a 1992 Civic Hatch, and the wife has a 2002 Honda Odyssey! I've often wondered if there was anyone out there that had quantified any mpg modifications to the Ody. Looks like you are on the track already.
Hopefully, I'll be able to replicate your efforts and provide more data points to base conclusions on. I've just got to call a local sign shop (which I've neglected to do yet).
Thanks for reporting all your work - it's an inspiration and great data generator. :clap:
NEW BOARD NOTE:
For some reason if you edit the message, it messes the html tag stuff up. I noticed this the other day and had a time with it. To fix it - edit the original message and take out all but the link and put [img][/img] before and after, respectively. It should fix it until you try and edit the message again.
Oh and a question: in one of your posts you say
I blocked off the intake to the intake air cooler and rerouted the radiator exhaust out to the front wheel wells through the drive train openings on the sides of the engine compartment like I did on my Civic.