'97 Jeep Cherokee XJ 4x4 overland rig

[mannydantyla]

Originally Posted by freebeard

The relief you show requires major surgery, extend the wheelbase or re-hinge [suicide] the door. Less radical is the Honda Insight and others with a rolled lip.

Ok, let me make something clear...

That's not going to happen.

I'm not going to do anything too radical! I'm not going to have a NASCAR air dam that scrapes the ground. I'm not going to build a giant boat tail that another driver will drive into.

First and foremost, this is an off-road rig. Period. I really do appreciate your advice but please stop promoting silly ideas, this isn't aerocivic. (I really hope that doesn't come across as too rude)

As for the fender indentation to promote airflow reattachment, I'm just going to smooth the transition behind the front tires by bending the sheet metal a little, maybe a little welding, but it will stop at the door. It wouldn't be as sculped as the older Honda Insight's.

Basically, I would just flatten and smooth this section here, pulling the lower corner to the inside.



And for the rear wheels, I'm still thinking. Right now the plastic bumper end caps are still on, but the ends facing the rear wheels were cut open when trimming the fender flairs so now they're like big air scoops. They should probably be removed, and the sheet metal behind it "cut and folded." What do you think?





Just for fun, check out how I drove ~1,500 miles on an overland trip last year:



I think this year I'll figure out a better way to store the spare tire, lol

[freebeard]

I really do appreciate your advice but please stop promoting silly ideas, this isn't aerocivic. (I really hope that doesn't come across as too rude)

Come at me, bro.

Silly? It was intended as Reductio ad absurdum. I guess it worked?

[mannydantyla]

Originally Posted by freebeard

Come at me, bro.

Silly? It was intended as Reductio ad absurdum. I guess it worked?

I guess it did work. And yes I had to look up Reductio ad absurdum.

This is my daily driver, it can't be a concept vehicle, I'm just trying to get reasonable fuel economy

[mannydantyla]

It's not going to get me better MPG, because I've already disabled the A/C (still need to pull the compressor and replace it with an idler pully), but I've decided to paint the roof white to keep summer temps down inside the cabin.

[oldtamiyaphile]

Originally Posted by mannydantyla

but I've decided to paint the roof white to keep summer temps down inside the cabin.

http://ecomodder.com/forum/showthrea...oof-35655.html

[mannydantyla]

Originally Posted by oldtamiyaphile

http://ecomodder.com/forum/showthrea...oof-35655.html

Hmm, maybe in the very center, like between the roof rack rails

[elhigh]

You could look at the movement of your tires as they rise into the wheel wells. If you can close any of that gap without interfering with the movement of the tires, it's worth doing. Otherwise those wheelwells are just big pockets full of turbulence, making noise and eating energy that could otherwise keep you moving down the road. In your flexed photos, it didn't look like there would be too much interference if you brought the lips of the rear wheel wells down a couple of inches.

The rear spoiler above the liftgate could help, but experiment with the angles. So long as airflow stays attached it's helping.

An option for aero would be a hitch mounted tailgater with an aerobox built onto it. Build it right so it's collapsible when you get to the trails, move it inside the truck for wheeling.

An air dam would probably yield quick, cheap results, but since you want to keep this thing good for the trails you'll need to do some fabbing to make it easy to remove and stow inside the vehicle.

Like others said, instrumentation. You can't know what works if you don't know how it's working. Having instant feedback also makes it a lot easier to adjust your own driving style. A Scanguage 2 should plug right in to your OBDII port and allow you real-time info on your fuel burn rate, engine temperature (important to know if you're experimenting with grille blocks), etc.

[mannydantyla]

Originally Posted by elhigh

You could look at the movement of your tires as they rise into the wheel wells. If you can close any of that gap without interfering with the movement of the tires, it's worth doing. Otherwise those wheelwells are just big pockets full of turbulence, making noise and eating energy that could otherwise keep you moving down the road. In your flexed photos, it didn't look like there would be too much interference if you brought the lips of the rear wheel wells down a couple of inches.

The rear spoiler above the liftgate could help, but experiment with the angles. So long as airflow stays attached it's helping.

An option for aero would be a hitch mounted tailgater with an aerobox built onto it. Build it right so it's collapsible when you get to the trails, move it inside the truck for wheeling.

An air dam would probably yield quick, cheap results, but since you want to keep this thing good for the trails you'll need to do some fabbing to make it easy to remove and stow inside the vehicle.

Like others said, instrumentation. You can't know what works if you don't know how it's working. Having instant feedback also makes it a lot easier to adjust your own driving style. A Scanguage 2 should plug right in to your OBDII port and allow you real-time info on your fuel burn rate, engine temperature (important to know if you're experimenting with grille blocks), etc.

Aerobox? I do plan on fabing a hitch and/or rear bumper mounted spare-tire carrier. So if it could carry the spare tire then win win. I still need to see out the rear window though as my side mirrors are not very good for that.

I already have an air dam. Keeping the factory air dam is kinda like a mod since 99% of cherokee owners who offroad them will take the air dam off first day they buy it. Maybe I could extend it but it would have be be with a softer material then plastic so it can hit rocks and sticks and stuff and bounce back.

Would you recommend the ScaneGauge^e if I wanted to save a little money? It's like $50 cheaper.

[elhigh]

If the E says it'll talk to your XJ then it should be 95% of everything you could ask for. It'll leave a few features off that you might use if you were a serious ecomodder, but you sound more like a serious weekend wheeler. The E should suit you. It'll provide:
- water temp (you want that for grille blocks),
- avg and instant MPG,
- MAP,
- Intake Air Temp (very useful if you want to try a WAI for highway pseudo-lean burn cruising),
- TPS (also useful for WAI)

I think an E would do you pretty well.

For a softer but durable air dam, conveyor belt material if you have an easy source. If you don't have an easy source, find your nearest Rural King or Tractor Supply and pick up some baler belting. You may need to double it up to make it stiff enough to hold up against the wind of driving down the highway, but sturdy? Shoot yeah: it's designed to work inside a hay baler. It's tough enough. And if you have some left over you could extend sides down from your rockers, side skirts that, like the air dam, will give when you bump into something, but bounce back from it.

The hitch carrier can come right up to under the window and stop. All it has to do is fill as much of the wake behind your rig as you can make it, while tapering in from the sides (and up from the bottom) gradually enough to prevent turbulence from forming. Look up the Aero Template to see what an "idealized" aerodynamic profile looks like. You don't have to apply the entire template to your entire car, improvements can be made just be tweaking here and there. It's what the automakers have been doing this whole time anyway.

Also read up on what Aerohead has done, I think the guy is a literal rocket scientist. Even if he isn't, he's done what looks like Basjoos-level aero work on an otherwise stock T-100.

[freebeard]

If you can lure aerohead into the conversation, great. I'd point to the NASA van and Mair



Something the size of the spare tire in the middle of the back is the opposite of what you want, a box cavity. Consider the Trailer Tails on the back of big rig trucks. They are flat and collapsible because reasons, but something that is curved to follow Mair on the top and side, and flat on the bottom would outperform a half-height boat tail.

Could you put the spare tire on the front bumper?