Grille block v2.0 a success! (kinda long)
 

As those who saw my first post (https://www.gassavers.org/showthread.php?t=2708) know, I did some aero mods to my car before coming here and was less than impressed with my initial results. You can see in my vehicles fuel log that I got no real improvement out of my first attempt at a grille block and underpan. My instant MPG was higher at some points of my drive but overall not much changed. I've put some pics up here: https://rides.webshots.com/album/557657592RszklZ

I was even further disappointed when I left the bellypan off after doing an oil change (ran out of time on the weekend). I decided to try an informal A-B test at that point so removed the grille block as well and put the stock air dam back on. On my in-dash MPG readout I noticed no difference except on one stretch of my drive, and my mpg at the pump was the same. :confused:

I'm not entirely sure at this point what I did wrong with the first setup, but I decided to try again with grille block v2.0. Doing this during the week, a grille block was all I had time for. This time I put the grille block on the outside and went for total blockage of the upper grille while leaving the lower open.

After just one day with it on, I am calling this one a tentative success. Even with only the block I have seen FE gains on my dash readout throughout my commute. I was very impressed when I saw gains of several mpg in places where I had not seen a difference between my first mods and stock. So, it seems that the placement of the blocker matters alot more than I first thought.

So, now I am looking for ideas on where to go next.

I still want to work on the underside, but what was wrong with my first bellypan design? The frontal area was no different than with the air dam and I thought for sure that it would be cleaner for the airflow. I do intend to include wheel spoilers on my second bellypan though.
Or would it be just as/nearly as effective to just extend the stock airdam out to the sides and incorporate it into the bottom of the wheel spoilers but leave the engine bay open? (you can see the stock air dam in the photo of the second grille block)

I also want to try sealing in the area between the spare tire well and the rear bumper cover. It's like a big scoop back there and I have noticed dirt and gravel :eek: collects up there, so it's gotta be trapping some air.

Another idea of mine is to add a hood vent (a'la GT-40, but in minature) to let underhood air fill in the low pressure area at the front of the hood and shift a bit more of the airflow to over the car instead of under it.

Of course, there's always wheel skirts. It's a Chrysler sedan, so they're right in character! :cool: Could probably work some kind of gap filler in the front wheelwells.

Awesome post. I would focus on the rear wheelwheels and bumper first and then improve your front underbelly pan. I used a rubber sheet that my uncle had used to line his pond to cover my front bumper scoop on my '97 civc. It is alot easier to use than sheet metal because it forms for you. I can't seem to find the corregated plastic everyone else uses. I would use some of that on underbelly pan and some rubber mat up front on your lower bumper. What type of engine do you have? I am a mopar guy and know quite a bit about other possible engine modifications you could get off of other years...

The hood vents are a great idea. First off, the larger pressure difference allows the air intake for the radiator to be smaller. Secondly, you can pretty much seal up the bottom of the engine compartment without ruining the radiators efficiency!

Well, I did a bit more. Rear fender skirts and rear bumper gap fill.

https://rides.webshots.com/photo/2092...83184085sPVndM

https://rides.webshots.com/photo/2848...83184085NkIMYI

All cardboard and duct tape for now. The paint seems to help the cardboard deal with water better and also keeps the car looking nice (for having cardboard duct-taped to the side)

I've only had one days driving on it (70mi) so I don't have concrete FE numbers from the pump yet, but I can say that I have seen mpg numbers on my dash readout that I never used to see along certain stretches of road that I watch. She also seems to roll easier downhill and I noticed better pull when passing. :D

My avg mpg reads 28.9mpg for todays drive (I reset it after filling up this morning). With just the grille block I have been seeing low 27's on the average readout, and got over 28 at the pump. The average readout is always 1-2mpg below my actual which makes me wonder if my injectors need cleaning a bit or if the programming is just off.

I'm hoping I can break 30mpg soon on my normal drive with a little more aero work.