Jeep Cherokee Aeromods

[achang1]

NICE! im gonna have to get on this, whered you get stainless or gavelized sheet metal?

[FastPlastic]

It's galvanized sheet metal I found in the Home heating and cooling section at Lowes. It's a little weak so you have to reinforce it in places (still need to add a cross brace behind my skid plate, has more play then I like). But it's cheap, lightweight and easy to find (about $7 a sheet).

[FastPlastic]

So I decided I wanted to run five of the grill blocks but after testing I found it was getting a little warmer then I wanted. After look at the grill and the openings I had left. I found that it wasn't getting a whole lot of air through the radiator. Most of it was traveling around it. So I used a little galvanized steel to redirect some of the air. I went ahead and painted it because it's behind the grill and harder to get to then the others.

Sadly in the process of putting the grill back in I managed to crack one of my grill blocks, Oops. A little 2000 pound epoxy should hold it till I cut a new one.

[Red]

Weird, I would have a figured a 98 XJ would have had the factory radiator air deflector things stock. My TJ has two heavy plastic/rubber flaps that flank the evaporator forcing air into the rad and not around.

[achang1]

weird, why didnt you do the deflector all the way up?

[FastPlastic]

Originally Posted by achang1

weird, why didnt you do the deflector all the way up?

I didn't do it all the way up because I couldn't find a good way to secure it. I looped the piece around the pipe leading to the radiator and have it bent like a spring so it stays in place.

[FastPlastic]

The next part of the under body work. I noticed a large hole on the driver side axle under the spring. From the looks of it the air flows over the axle and in to the hole, then has no place to go. The lower section had a lip I could wrap around so I'm not worried about that staying in place. But the upper section didn't, so all I did to secure it was cut the metal wider then the opening, then bend the sides a bit, giving me a decent pressure fit. It takes a screw driver and a lot of prying to get it out. So I'm guessing I won't have any problems with it. I also covered up the passenger side while I was at it.

[nascarnation]

Looks nice, great work!

[Smoove]

You are very thorough - nice work! Have you seen any improvement yet?

Also, would your axle deflectors be of any benefit to the rear axle or maybe even the trans cross-member? Or are you just systematically working your way back?

[MazdaMatt]

I just used those same galv'd HVAC sheets to build rad ducting into my race car. Very easy to work with, light weight and reasonably stiff when you've added some seams. If you had one of those rollers used to reinforce floor boards on the "custom garage" shows, then it would be pretty stiff, i think.

[FastPlastic]

Originally Posted by Smoove

You are very thorough - nice work! Have you seen any improvement yet?

I haven't had time to take it out on the highway yet. But I have noticed it rolls a little farther in town then it use too.

Originally Posted by Smoove

Also, would your axle deflectors be of any benefit to the rear axle or maybe even the trans cross-member? Or are you just systematically working your way back?

I'm working my way back. So far I think I've covered most of the bases from the front axle forward. Been looking farther down and haven't decided how it's going to go (not a fan of drilling holes, Haven't so far). I plan on doing similar setups for the rear axle and cross member. And if I can I would like to do a full pan across the middle (Haven't decided how I'm going to mount it yet).

[FastPlastic]

Ok so I took the Jeep down to Des Moines the other day (about 100miles round trip). I felt like something was holding it back a bit. The trip down doing 55mph I just barely hit 25mpg. I was looking at the setup for the mechanical fan which is located in the middle. I recently added the center grill block again. Could I be limiting the air flow to the fan enough that it's working harder then normal? I also noticed the gas mileage was slightly better a few MPH faster (more air flow?). I plan on doing some testing this weekend.

Am I crazy thinking this could be the problem?

[achang1]

i dont see how a grill block will cause the mechanical fan to work harder. it's tied into the belt system, so as the engine revs faster, the fan turns faster. if you dont mind a very involved modding, what you can do is replace the mechanical fan with an electric one from a Taurus/Sable. there's a post on that somewhere here. it wont be automatic, so you have to turn it on manually, or have settings which you will self adjust.

to your drag issue, could it be that your aero mods are causing more drag?

its kinda odd, ive been feeling alot of struggle on the highway on my windstar. i dont know why but it seems i get worse mileage then i do in the city. also my cars have multiple drivers and i am the more hypermiller of the rest.

[FastPlastic]

I guess the reason I'm wondering if it's the problem is when you block a fans intake doesn't the fan have to work harder to move the same amount of air? I tried placing a piece of card board behind a box fan and it sounds like the fan slows down/works harder. I heard somewhere that you can burn out a box fan if it tips over and can't get the air flow it needs. Would that not mean that the extra energy needed would be directly transfered to the engine?

[aerohead]

Originally Posted by FastPlastic

I guess the reason I'm wondering if it's the problem is when you block a fans intake doesn't the fan have to work harder to move the same amount of air? I tried placing a piece of card board behind a box fan and it sounds like the fan slows down/works harder. I heard somewhere that you can burn out a box fan if it tips over and can't get the air flow it needs. Would that not mean that the extra energy needed would be directly transfered to the engine?

With the T-100,I was very careful with the grille block with respect to the fan clutch.I actually drilled and saber sawed away the section of bumper directly in front of the fan/drive,so I would guarantee air flow over that clutch.If she gets hot,she'll lock up.and you'll have all that extra fan drag the clutch was supposed to eliminate! That cost the Pinto a full mpg at 70-mph.

[FastPlastic]

Ok I'm starting to look at the under body past the front axle. I'm looking for some opinions from those that know more about aerodynamic drag forces. Just past the axle there are several pieces hanging down. The exhaust takes a quick turn towards the passenger side. Plus the front drive shaft hangs down on the driver side. I can clear the exhaust if I start at the level of the cross brace around the middle of the jeep. But the suspension prevents me from getting closer then about 1 to 1-1/2feet from the front axle. If I just do a strait panel the air would flow over the panel rather then under. Would it create too much drag if I curved the panel up in front of the exhaust? I would still need to cut an opening for the drive shaft to clear.

The goal would be to continue the panel all the way back to the rear axle so it would cover over a lot of stuff sticking out.

I appreciate all the help I can get!
Phil

[aerohead]

Your illustration looks real good! With the upswept radiused leading edge,the flow should transition right onto the new panel just like the flow illustrator depicts.I'd go for it.If the driveshaft requires a lot of vertical articulation that might strike the panel,you could break it into two separate pans without losing much to drag.Your work looks great,look forward to your next installment!

[FastPlastic]

Originally Posted by aerohead

Your illustration looks real good! With the upswept radiused leading edge,the flow should transition right onto the new panel just like the flow illustrator depicts.I'd go for it.If the driveshaft requires a lot of vertical articulation that might strike the panel,you could break it into two separate pans without losing much to drag.Your work looks great,look forward to your next installment!

Just the man I was looking for. Thanks for the help!

I jacked the car up a ways and the drive shaft won't give me problems with the height I'm looking at. Just have to cut out a U for the shaft to bounce in. Plus my design is going to mount with hooks on the back and two bolts on the front. So it should take 2min to take off for repairs. All without drilling any holes!

Phil

[aerohead]

That's the best news,'cause you pick up a fraction more efficiency not having the split pan.Easy on/off a big plus also.Look forward to new pics as progress develops.I think you're teaching a lot of the members clean fabrication techniques,and will probably never realize how many will benefit from your careful work.

[achang1]

yea i was gonna say, jack the body all the way so the shaft and axles are at the max
im curious, how strong can velcro get? because im wondering if i can make body panels that attach with velcro.