New 2015 Renegade
 

So, I'm looking at doing a full belly pan out of diamond plate. Besides doing that, what other suggestions would you guys have? I've tried to do the best research I can on here but that's all I can really come up with besides take Inc off the roof rack. Is that going to hurt my mpg that much leaving the stock rack pieces on?

Welcome to Ecomodder.

The longitudinal rails are Okay, but remove the cross-rails if possible.

As for the larger question, what are your parameters? What do you want to achieve and how much pain will you go through to achieve it?

The vehicle can be divided into drivetrain and aerodynamics; the third element being the 'nut behind the wheel'.

It being a late model there isn't a lot of 'low hanging fruit'. For instance it has spats in front of the front wheels already. To exceed the current performance would require radical lowering and lengthening. At least partial fender skirts, at least on the rear. Your belly pan will need to respect engine cooling needs.

It might be fun to extend the existing rear spoiler like a lot of hatchbacks do.

Do a forum search for examples.

Pizza pan wheel covers.

I'm not a fan of grille blocks, one sensor to turn on the fan fails and you could overheat and warp your heads.

I'm wanting to get as close to 40 mpg as possible. I am currently at 26 mpg for my first tank. Not sure what I should do to the belles Pam besides just run a custom sized full sheet of diamond plate under it.

If you "need" diamond plate, do an air dam. Plastic sheeting is what you want for an (aero, not armor) belly pan.

To achieve 40mpg, would require a full boattail, or bellypan/wheelspats/ mirror delete/bellmouth radiator shroud/tall, narrow tires with Moon disks/radical lowering.

It can be done.

40 mpg is not impossible, but as a fellow off-roadish car driver, the biggest ecomod is reducing average speed :D

I'm thinking wheel arch gap covers front and rear since I don't want to lower it. Also, I wanted diamond plate just because it won't melt like corrugated plastic would. Also wouldn't droop over time from the harsh AZ heat. I'm thinking of how to incorporate an air dam into the belly pan as one cohesive unit. Anything wrong with this train of thinking? An suggestions?

Not sure if wheel arch gap covers would work on the front, due to steering clearance. Incorporating the air dam into the belly pan seems to be a good idea.

Generally, the air dam keeps air out from under the car, and the belly pan smooths the flow. They can coexist, but if the air dam is lower than the pan, it decreases the efficiency.

If the belly pan extends forward of the air dam, that's a diverter which adds downforce in front.

Partial skirts won't help as much as lowering because they won't affect frontal area. Hangar door brush is a continuous brush available in 2" increments for length and would make the 'spray guards' you see on big trucks.

The front wheelwell has more drag than the rear but there is opportunity for an air curtain. See the new Ford trucks.

If you want diamond plate, that's what you should have.