Off road friendly aeromodding... My lil beast

[chillsworld]

Originally Posted by 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.

From 10mpg to 18mpg... NICE! For me though, I don't have the money or skills to swap in a manual tranny. I'm sure if I did a manual and 4wd instead of AWD tcase, I would see upwards of a 30% increase in FE while in RWD. Oh if only I had my own shop and a big bank account! A taco, that was quite the upgrade for you!!

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.

Unfortunately, a car payment isn't a financial reality right now... And finding a 4wd ranger, taco, frontier, etc in a cash and carry price has proved beyond difficult for me (I've been looking!). I know all too well, that I won't be happy with the end result when compared to what I could have. But the end result will be better than what I currently have. And I'm not really trying to improve my performance off the pavement, I'm trying to improve FE that will survive off the pavement. I have recovery straps, axe, shovel, come along, couple wooden blocks for leverage, etc. I know the limitations of my truck pretty well.

I have spent many an hour reading and drooling over at expeditionportal... My dream is to live out of unimog or similar vehicle

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... ...Use your armor sparingly, as a protection, not as a first resort to just power through an obstacle.

Totally agree, my thought was bashplates over the radiator, under the engine, and then the t-case. Then abs for places that don't need "protection". I'd love to do aluminum with HDPE, but that's after I prove to myself the increases in FE... I'll save up and do it right.

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

Yeah, this was a major source of confusion for me... I've tried finding someone that has a full belly pan on a similar vehicle, but all I can find are full on baja style racers and rock crawlers... Neither of which actually "seal" the hot air in because it's not an aero mod.

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.

Would dropping conveyor belt on the font and side really work? Seems like you would need it to be rigid, which would defeat the purpose of using it?

Tires are going to be a compromise.

I run A/T's, I don't play in the mud so no need for anything more considering it's a daily driver.

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.

Bottom is definitely too steep, I'm well aware of that... Why would you think the sides are too steep? They will be the same slope as the top.

I had considered a multi-part or removable unit, but honestly... That's just one more thing to store in the back of the SUV, something I was hoping to move away from. I guess when I get to that point, I'll play with cardboard and see what I can accomplish before deciding.

The burning question in the room: What fuel economy are you getting right now?

My last 180 miles was 14.4 mpg, and actually a little better given the taller tires. It was about a 60/40 split between hwy and 10-30 mph forest service roads/trails. The new EPA combined is 14mpg. Over the course of 5 months last year, summer and winter selections, I averaged right at 14mpg.

~C

[chillsworld]

Originally Posted by 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.

Yeah that was the idea, skid plate/belly pan combo. WIth an upper aero nose that comes out to meet the radiator skid plate.

I'm sure it wouldn't be hard to make it removeable, but how big of an improvement would I be looking at without sideskirts to prevent air from being sucked under and dirtying the air flow?

[BabyDiesel]

Subscribing. I think what you're doing is outstanding and will be worthwhile! This is looking to be an important thread for those of us who have offroad ready vehicles looking to boost our FE. The great thing is that small gains (.5 - 1 mpg) are huge to us Over the course of 10-20 years, a smaller 4wd would cost less overall... though I doubt you'll drive your luxury Exploder that long

Tires - look at 33x10.50R15 BFG AT KO's. My K5 will be getting these for all-purpose driving. A reduced contact patch for less drag, greater psi on the tread when offroad, reduced weight over a 33x12.50 and a greater height for reduced rpm on freeway. You'll be quad-winning

[jeff88]

Originally Posted by BabyDiesel

Subscribing. I think what you're doing is outstanding and will be worthwhile! This is looking to be an important thread for those of us who have offroad ready vehicles looking to boost our FE.

X2

As soon as I get the rebuild on my 4Runner done, I plan on doing some aero upgrades that I've wanted to do for a while as well (among other things ). Definitely interested to see what you come up with.

As far as tires go, you can look at the Goodyear Wranglers. According to Consumer Reports it has the best rating for LRR among the A/T and offroading tires. I've personally used them and I like the ride on them too!

[aerohead]

I think Hucho would tell you to just skip the nose.The Mountaineer's nose would shame some passenger cars.A little lower with the airdam would be good.
The tail is good,just as you've rendered it .A good compromise.
As to the wheel fairings,unless everything was really 'clean' up to them,and around them,they might just be embedded within turbulence.

[chillsworld]

Originally Posted by BabyDiesel

Subscribing. I think what you're doing is outstanding and will be worthwhile! This is looking to be an important thread for those of us who have offroad ready vehicles looking to boost our FE. The great thing is that small gains (.5 - 1 mpg) are huge to us Over the course of 10-20 years, a smaller 4wd would cost less overall... though I doubt you'll drive your luxury Exploder that long

Tires - look at 33x10.50R15 BFG AT KO's. My K5 will be getting these for all-purpose driving. A reduced contact patch for less drag, greater psi on the tread when offroad, reduced weight over a 33x12.50 and a greater height for reduced rpm on freeway. You'll be quad-winning

Well thank you very much for the encouragement! And yes, little gains for us can be epic haha... 5mpg is a 33+% increase

As far as my luxury exploder goes, I've had her long enough to rack up more miles than most people will ever do on a single vehicle... Perhaps more than they will do on multiple combined hahaha. So unless another vehicle falls into my lap or this one suffers a fatal injury, I'll have her long enough to see savings and pay off the cost if I keep it on the cheap! See below for tire talk...

Originally Posted by jeff88

X2

As far as tires go, you can look at the Goodyear Wranglers. According to Consumer Reports it has the best rating for LRR among the A/T and offroading tires. I've personally used them and I like the ride on them too!

Thanks to you as well for the encouragement!

My current tires have been upgraded to 31x10.5R15LT Wild Trac's, the tread's as aggresive as some AT's out there but WAY cheaper. And I'm getting great wear out of them. Of course, great wear means it will be a long time before I try to stuff 33's under there Unless of course I do some calculatin on RPM's and FE, and follow that up with some penny pinchin

Either way... I hope that my thoughts/ideas/questions, and hopefully follow through on some of them can help you guys (and others) in your search for better FE with your off roadin trucks.

~C

[oil pan 4]

You could do something like a conveyer belt air dam. Just hold it on with like 4 or 6 bolts and pull them off and throw the air dam in the back.
The 2/3 air dam on my suburban was good for nearly 1mpg.

Why would you want mud tires?
They are expensive, lower your fuel mileage, wear out quickly and need to be replaced well before they are worn out if you want them to be useable off road.

I say run highway tires or A/Ts with bad ass snow chains off road.
Or get a spare set of mud tires.
You can throw nasty set of snow and ice chains on a bald high way tire and do things the most radically aggressive, expensive mud tire with full complement of tread can barely do.
Another thing is most mud tires kind of suck in the snow and ice, I would rather have A/T tires. Ideally anything with chains.
Chains protect the side wall and shoulder to some degree too, plus if you do cut the side wall on a highway tire, who cares, its a cheap high way tire. If you cut the side wall on the most radically aggressive, expensive mud tire that still has full complement of tread, well sucks to be you.

[chillsworld]

Originally Posted by aerohead

I think Hucho would tell you to just skip the nose.The Mountaineer's nose would shame some passenger cars.A little lower with the airdam would be good.
The tail is good,just as you've rendered it .A good compromise.
As to the wheel fairings,unless everything was really 'clean' up to them,and around them,they might just be embedded within turbulence.

Ya don't say, putting cars to shame eh

In regards to the airdam, That's really all you think would be necessary? That in conjunction with a belly pan? Does the belly pan need to be as low as the air dam in order to prevent an eddie or swirling pressure zone behind the air dam?

~C

[chillsworld]

Originally Posted by oil pan 4

You could do something like a conveyer belt air dam. Just hold it on with like 4 or 6 bolts and pull them off and throw the air dam in the back.
The 2/3 air dam on my suburban was good for nearly 1mpg.

2/3 airdam? Like 2/3 of the way to the ground? Do you have any frame or structure to keep it firm at hwy speeds?

Why would you want mud tires?
They are expensive, lower your fuel mileage, wear out quickly and need to be replaced well before they are worn out if you want them to be useable off road.

I don't want mud tires, I said I don't play in the mud so I have no need for anything other than A/T's... Unless of course you consider A/T's to be mud tires, in which case I would say you need a redneck education on truck tires

[freebeard]

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This Commanderwagen has a field modification that is a roller for the front valance. Something like this could establish a low stagnation point.



Or maybe a high stagnation point and prow like a boat?

My current car is as low as I can practically get it, but for the next one I'm leaning toward a high ride height and heavily skirted and spatted wheels. A big problem for you will be the wheelwells.

For the belly pan, consider Grimco - Substrates: Max-Metal, MAX-metal HD. It's like Polymetal or OmegaLite, but the aluminum skins are .30mm, about twice as thick. It's available in 4x8 and 6x10 sheets.