Off road friendly aeromodding... My lil beast

[chillsworld]

I guess this can be a place for me to post my ideas/questions... And some day my build/results

Goal: To ecomod an SUV in a manner which maintains it's ground clearance, approach angle, departure angle, cooling system for long slow drives in the mountains, factory v8, and AWD/4WD. But to accomplish gains in FE which can justify the mods/expense

I love seeing all of these awesome cars and trucks getting crazy good FE! BUT, lowering, air dams, side skirts, full boat tails, nose cones, wheel skirts, etc etc, aren't always a good idea for some of us idiots

Vehicle: 1997 Mercury Mountaineer, 5.0 V8, automatic trans, AWD (kind of the exact opposite of what you want to start with hahaha)

Wish list of mechanical upgrades: exhaust/intake, electric rad fan, eventual swap of a true 4wd rather than awd transfercase (allow for RWD operation), and of course an OBDII gauge cluster for monitoring

Now on to the aeromods!

The Front:

Issues are ground clearance, approach angle, under body aero nightmare, big tires to cause turbulence (they are only 30" at the moment, but could be upt to 33" in the future), and frontal area.

This is my initial thought, could one merge a belly pan, offroad/prerunner bashplate, grill blocks, and an aero nose?


If the following two noses got naughty and had a baby... Would it be a good thing or a bad thing? From an FE geared aero standpoint. I know we try to cut flow under the vehicle with airdams and side skirts, but would this allow for a decrease in frontal load and a smoothing of under body airflow? Since dropping the truck, or adding an effective airdam aren't an option.



(Weather spotters Matrix was the first example I came to)



The Middle:
Haven't figure out how yet, but full length and width belly pan... Again, the issue is clearance. Otherwise I would just drop down to the ground and go clear under the rear axle



The Rear:

Issues are ground clearance, departure angle, the wicked bad aero of the body in general.

Idea is to design a boat tailish aero back, that will be mounted to a swing away bumper. Spare tire, recovery gear, jack, axe, etc etc to be stored in the tail section. My initial drawing has used the aero template from these forums, but I can't help but feel like it is shaped wrong when I look at the boat tails I see on this forum . I'm also wondering how far back it would need to go in order to see substantial gains in FE. Again, I know the bottom angle is wrong... But it's the necessary angle for departure. Ideas by Freebeard and Aerohead involve "wings" that drop from the bottom, or even having the lower portion adjustable for hwy vs "rubicon clearance" as aerohead described it haha



Any thoughts on shape or length would be greatly appreciated. The sides would be the same sloping curve as the top, with all seams being rounded as opposed to "creases". A rear pan/diffuser would help assist air along it's path to the underside of the tail, although design of that unit hasn't been considered yet. Nor do I know if any treatment behind the wheels would be worth it?

I have read through many pages of comments and designs here... And I totally get the ideas, just not sure how to apply them to my truck.


Thanks so much in advance to any responses, and the community at large for all the inspiration!

~C

[Cobb]

Does it need to be aero to save fuel or money? How about a samurai or tracker converted to a vw diesel running on recycled veggie oil?

[mcrews]

Get a scangauge. Half of your gain will come from driving smarter! See link in my signature.
Think about upsizing tires to lower rpm if doing a lot of freeway
Raise psi when on road.

[chillsworld]

Originally Posted by Cobb

Does it need to be aero to save fuel or money? How about a samurai or tracker converted to a vw diesel running on recycled veggie oil?

Oh, I love Sammy's with Diesels... Nothing quite like getting 35mpg with giant mud tires on haha. And I'm a huge fan of WVO as well! If I had a diesel, I wouldn't even care about FE cause I'd def be rocking WVO. But I'm stuck working with what I got... So I'm gonna see what I can squeeze out her via aero and simple mechanical upgrades.

-C

[chillsworld]

Originally Posted by mcrews

Get a scangauge. Half of your gain will come from driving smarter! See link in my signature.
Think about upsizing tires to lower rpm if doing a lot of freeway
Raise psi when on road.

I'll be getting a gauge for sure... Saw a minimal increase with current tires, but all it did was get me back to where I was when the truck was healthy. When these wear down I'll be looking for lighter wheels and taller tires (33" if I don't have to trim fenders). I'd love to get a couple hundred rpm lower @ hwy speeds... In the mean time, I'll see if I can play with basic mechanical and aero

-C

[cRiPpLe_rOoStEr]

Originally Posted by chillsworld

This is my initial thought, could one merge a belly pan, offroad/prerunner bashplate, grill blocks, and an aero nose?

Why not? I guess the most challenging part would be making it stout enought to stand to the off-road environments, but still seems manageable.

[2000mc]

Originally Posted by cRiPpLe_rOoStEr

Why not? I guess the most challenging part would be making it stout enought to stand to the off-road environments, but still seems manageable.

Originally Posted by chillsworld

The Middle:
Haven't figure out how yet, but full length and width belly pan... Again, the issue is clearance. Otherwise I would just drop down to the ground and go clear under the rear axle

i dont have experience w/ off road trucks, but with atvs a good glide plate is worth several times the ground clearance that it takes away. so long as it can take the punishment, you can let it scrape, drag, and the obstacle hardly slows you down. hit something you wouldnt have the ground clearance for already, your momentum will carry you over.

[aardvarcus]

I am doing something similar, as I needed a good fuel economy vehicle to get to work and back, but I wanted more capable machine both on-road and off-road. I started with a Chevy 1991Regular Cab K2500LD 5.7L V8 that I already had that always got 10-12 MPG, and was able to get it up to 18 MPG average. That involved (in order of magnitude) a transmission swap (auto->manual), driving style, tire swap, air dam, fluid changes, etcetera. I eventually realized I would be better off starting with something that fit my needs better, so I got a 2005 Toyota Tacoma Access Cab 2.7L 5-Speed 4x4. Right out of the gate I instantly got 26+ MPG. The Tacoma is no slouch in the off-road world either.

I am not trying to dissuade you from “running what you brung” as that is always a good idea, just make sure you are going to be happy with the finished result before you put lots of time and effort into it. I have been there done that and it’s not fun. Also don’t discount the capabilities of your stock vehicle, get some decent recovery gear and a buddy and go see what your vehicle can do before you spend a bunch of money and time improving its off-road abilities. If you don’t already, look on expeditionportal, plenty of people on there doing incredible things with almost stock vehicles. Too many sites telling you to never even leave the pavement unless you are locked, lifted, 37s, and one tons.

I have had many of the same ideas you have had with regards to underbody armor, but the trick is to make it strong enough to take the abuse, but light enough not to kill FE and acceleration. No point in the V8 if you have so much weight bogging it down that it drives like an I4. My idea is to use selective steel reinforcements in key areas, and to span the majority using aluminum and HDPE. Look up what many of the tube buggys have done, weight is a big deal to them and there are lessons to be learned on design and construction. Use your armor sparingly, as a protection, not as a first resort to just power through an obstacle.

Mounting is always going to be an issue. Also, don’t create an oven, you need to realize the exhaust is like a giant heating element and if you trap the exhaust up inside a belly pan it turns into an oven. (An oven with your gas tank inside.) Plus the heat generated by your V8 exhaust is orders of magnitude more than generated by a hypermiled Honda Civic. I don’t suggest running the belly pan under your exhaust, it is possible but it takes some serious head scratching.

For the approach angle/air dam dilemma, one method is to use something flexible, like conveyor belt, as the dam so that it can take some abuse. Another method is to use something that is quickly removable. Also, you could do both, which is my preferred solution.

Tires are going to be a compromise. Either get all terrains, or run two sets one on-road only and one off-road only. At least that way you don’t wear out your offroad tires pounding the pavement. Also, I have found siped road tires do much better on slick roads and in light snow than deeply lugged off-road tires with minimal or no sipes.

The top part of your boat tail looks good, but I think you have the sides and bottom too steep. Consider making a small solidly mounted boat tail (that doesn’t come out past the bumper) which can’t affect offroad abilities and would have room for your spare, and then making a removable tail extension.

The burning question in the room: What fuel economy are you getting right now? If you don’t have one, get a ultragauge or other gauge and start learning your car’s patterns and rhythms. Miles from pavement, you need to know when something is wrong well before the car throws an check engine light at you.

[elhigh]

You might need to get this fabbed up custom, but a stout aluminum skid plate for your nose can serve on-road duty as a partial belly pan.

I wonder how hard it would be to make an air dam that was easily demounted for off-road duty.

Cheap smoothie discs for your wheels wouldn't affect your offroading at all. If you lose one on the trail, well, I did specify cheap.

[chillsworld]

Originally Posted by cRiPpLe_rOoStEr

Why not? I guess the most challenging part would be making it stout enought to stand to the off-road environments, but still seems manageable.

I think that would be relatively easy to do on the nose, the lower portion would be metal... The upper portion would be foam/fiberglass, but it would be up out of the danger zone for impacts. Truly, even in a fender bender I think it would go undamaged just like they survive hits on rocks. I think weight is the only issue.

Originally Posted by 2000mc

i dont have experience w/ off road trucks, but with atvs a good glide plate is worth several times the ground clearance that it takes away. so long as it can take the punishment, you can let it scrape, drag, and the obstacle hardly slows you down. hit something you wouldnt have the ground clearance for already, your momentum will carry you over.

Rock bouncing, an idea that scares the bejesus out of me hahaha. But I agree, it's one of the reasons I had originally looked into this idea a couple years ago... Lift kits for my particular truck are non-existent And now seeing all the talk of belly pans on here, has made me think about its potential again.