Aerodynamics

[mmc757]

We all know our gas mileage *****...thats the price we pay for a bullet proof drivetrain, a frame beefy enough to support two ***** elephants gettin it on, and aerodynamic qualities similar to those of a brick.

Of those three primary problems, I'm wondering if we can get some gains by working on the aerodynamics issue...

My hobby vehicle is a sport compact, and Ive been reading up a lot lately about undercar aerodynamics...depending on the model, there are lots of cars that can pick up 3-6 mpg with a smooth underbody and properly designed rear diffuser and front splitter.
Obviously our ground clearance will cause different airflow characteristics than a car thats lowdown, but the principles should still apply I think.
For a Jeep, I dont see why it wouldnt be possible to kill two birds with one stone here, and build a full underbody pan that serves as both an aerodynamics aid and as protection on the trail...
Obviously it would be desirable to minimize the impact on ground clearance, but I dont think that would be too difficult.

So the question is a three-parter:
1. Has anyone with guards underneath noticed an improvement in mileage after installation?
2. Any other thoughts on the subject?
3. What other ideas have you had to improve our aerodynamics?

 

[LibertyTC]

Overall I think tune ups w/clean plugs air filter/throttle body, IAC, & synthetic motor oil a few Lbs more air in tires, will do more than worry about aerodynamics.
Your fuel injectors also should be cleaned out to improve mileage. I use Chevron Techroline.
Lighter foot and reduce KJ weight as well, when possible.

 

[Jeepman56]

For me with full skids underneath I did not notice any increase in mpg. I believe that is attributed to the increased weight and partial underbody coverage, however, in my opinion I do not think that the aerodynamic gains would be worth what a thinner/lighter full underbody system would cost to make. Additionally, since we are unibody I am not sure that a full front-to-back wall-to-wall system would work unless it had some play in it which would most likely negate the aero porpeties anyway. That being said it is always good to think outside the box and see some new ideas bouncing around so maybe give it a shot and see. I am sure others will weigh in on this as well.

 

[mmc757]

Weight is obviously an issue if the intent is to double as skids...maybe an option would be to build two separate sets, one for DD use out of lightweight material such as ABS or thin aluminum, and the other out of something more substantial for offroad use. Assuming the panels would bolt up to a rail system, building a second set would be a breeze once the first set is built.

 

[J-Thompson]

you could build them/it out of UHDPE leaving the skids in place and covering them up with the UHDPE
very slick and very strong

 

[Dave]

you could build them/it out of UHDPE leaving the skids in place and covering them up with the UHDPE
very slick and very strong

Interesting idea.

In reality you just can't compare a 4,200lb Jeep that is shaped like a brick to a car. My car weighs 3,200 lbs and sits low to the road and gets 29-30 mpg without trying. That's 10 mpg better with the same size v-6. Totally different animal and it is aerodynamic, lower to the ground, and weighs 1,000 lbs less than the Jeep. But still I would rather drive the Jeep as it is more fun and will go anywhere. The car, not so much.

Do like TC said and keep it tuned up. Plugs, air filter, PCV, clean intake, etc.

Dave

 

[Ry' N Jen]

Aerodynamics?
In our case I think it would be useless!
Having a ski box, basket, winch, lights, and all other Jeep goodies kill that idea!

 

[J-Thompson]

Interesting idea.

In reality you just can't compare a 4,200lb Jeep that is shaped like a brick to a car. My car weighs 3,200 lbs and sits low to the road and gets 29-30 mpg without trying. That's 10 mpg better with the same size v-6. Totally different animal and it is aerodynamic, lower to the ground, and weighs 1,000 lbs less than the Jeep. But still I would rather drive the Jeep as it is more fun and will go anywhere. The car, not so much.

Do like TC said and keep it tuned up. Plugs, air filter, PCV, clean intake, etc.

Dave

I got the idea when I was looking under the VW and thinking how easily a chunk of blow out could kill so may of the "parts" under there
The next day at work I had to use/fool with UHDPE
and even the 1/2" thick stuff is easy to work with as far as cut and drill
and dont think you can grab it

 

[Ry' N Jen]

I got the idea when I was looking under the VW and thinking how easily a chunk of blow out could kill so may of the "parts" under there
The next day at work I had to use/fool with UHDPE
and even the 1/2" thick stuff is easy to work with as far as cut and drill
and dont think you can grab it

On my Mini, I've been using Teflon over top of my skid plates for years!
Not only does it "Skate" over everything, it extends the life of the actual skid plate!
Not cheap, but less expensive than replacing the engine/transmission sump!

 

[mmc757]

Interesting idea.

In reality you just can't compare a 4,200lb Jeep that is shaped like a brick to a car. My car weighs 3,200 lbs and sits low to the road and gets 29-30 mpg without trying. That's 10 mpg better with the same size v-6. Totally different animal and it is aerodynamic, lower to the ground, and weighs 1,000 lbs less than the Jeep. But still I would rather drive the Jeep as it is more fun and will go anywhere. The car, not so much.

Do like TC said and keep it tuned up. Plugs, air filter, PCV, clean intake, etc.

Dave

Thats true of course. All the things that make this vehicle as great as it is are also the things that cause the bad mileage so its a trade off. My thought process is that if its built properly, the worst case scenario is still going to be an improvement...if nothing else I would have rails to mount serious skid plates onto. Best case scenario, I pick up a couple of MPG's and the project pays for itself in a couple thousand miles.

 

[tjkj2002]

Not going to happen if your lifted,it will only get worse.Plus you want airflow under these things because you have so much under there that is still air cooled,plus that solid rear axle just kills any hope of what you would want and sounds like alot more work then it's worth.

You want better mpg's it's as easy as sell the Jeep and get a econobox,will get you better mpg's but not cost effective then keeping a paid off or nearly paid off vehicle that get's less mpg's.

 

[retmil46]

Ummmm, get the engine and drivetrain out of a wrecked CRD?:hidesbehindsofa:

 

[tjkj2002]

Ummmm, get the engine and drivetrain out of a wrecked CRD?:hidesbehindsofa:

Yeah then spend another $5000+ to make it work,then another $5000+ so it won't self destruct.

 

[Ry' N Jen]

Yeah then spend another $5000+ to make it work,then another $5000+ so it won't self destruct.

Not to mention all the associated "Scheduled Maintenance" Diesels require on an
on going basis!
(Slightly off topic here... My Old man brags about how great his Diesel VW
Jetta wagon is and how he gets 1200+ KM/746 miles per tank, but he doesn't realize that in the last six years he has spent $9500.00 in "Scheduled Maintenance" just to keep his VW in top condition! Well, in the last 5 years, we have spent less than a ⅓ compared to his VW!)
Diesels are Artificial economy!

 

[J-Thompson]

Not going to happen if your lifted,it will only get worse.Plus you want airflow under these things because you have so much under there that is still air cooled,plus that solid rear axle just kills any hope of what you would want and sounds like alot more work then it's worth.

You want better mpg's it's as easy as sell the Jeep and get a econobox,will get you better mpg's but not cost effective then keeping a paid off or nearly paid off vehicle that get's less mpg's.

unless your commute goes from <8 miles a day to over 70

 

[mmc757]

Here we go...thread getting out of control because people are overreacting. If your not interested in a discussion about aerodynamic improvements to the vehicle, feel free to ignore this thread. It should have been clear from my first post that I'm not trying to change the world here. I understand why the mileage ***** and understand that its just the price we pay, but that doesnt stop me from thinking about ways to improve it. I'm actually a little disappointed...usually this forum is above this sort of behaviour.
This is my teenage daughters vehicle and I couldnt think of anything I would feel safer about sending her out into the world in, but at the same time she doesnt have much money so if I can find ways to bump up her MPG's a few than its worth consideration.

Every mod anyone does to any vehicle is nothing more than an effort to improve something they think could be done better...this is no different from that perspective than installing a lift, or a cargo shelf, spotlights, or anything else that is discussed regularly here.
Take a look under the vehicle...theres lots of room for improvement.
Since the title of the thread was left generic, feel free to discuss other areas of possible improvement:
How about replacing the side view mirrors with cameras? How about an air dam in front of the wipers to smooth out the transition between the hood and windshield?

 

[Ry' N Jen]

Here we go...thread getting out of control because people are overreacting. If your not interested in a discussion about aerodynamic improvements to the vehicle, feel free to ignore this thread. It should have been clear from my first post that I'm not trying to change the world here. I understand why the mileage ***** and understand that its just the price we pay, but that doesnt stop me from thinking about ways to improve it. I'm actually a little disappointed...usually this forum is above this sort of behaviour.
This is my teenage daughters vehicle and I couldnt think of anything I would feel safer about sending her out into the world in, but at the same time she doesnt have much money so if I can find ways to bump up her MPG's a few than its worth consideration.

Every mod anyone does to any vehicle is nothing more than an effort to improve something they think could be done better...this is no different from that perspective than installing a lift, or a cargo shelf, spotlights, or anything else that is discussed regularly here.
Take a look under the vehicle...theres lots of room for improvement.
Since the title of the thread was left generic, feel free to discuss other areas of possible improvement:

How about replacing the side view mirrors with cameras?

If your daughter doesn't have much money, then how do you expect here to afford buying camera's and monitors in place of side view mirrors?
Then there is the placement of the monitors within the vehicle. Where would you propose to place those?
More distractions for the driver...
Not to mention a teenage driver who doesn't have allot of driving experience
to start off with!

How about an air dam in front of the wipers to smooth out the transition between the hood and windshield?

Vehicles are designed certain ways for a reason, once you start messing around with an area such as the cowl area, you can create more problems with the air flow and the vehicles aerodynamics!
Not to mention air flow to the HVAC system.

It's a Jeep.

There is no such thing as Aerodynamics with a vehicle shaped like a brick.
Then there is the weight of the KJ. That too effects the mpg...

Buy her a Toyota Prius if you want aerodynamics and better fuel economy.

 

[mmc757]

I thought I made it pretty clear that I'm not looking for a prius...Please try to keep comments constructive.
An underbody setup like I'm thinking about could be done for under a couple hundred dollars. At $4/gallon, a 2 mpg bump would save $8 every tank. At a tank a week thats an extra $32 in the wallet every month, and the project will pay for itself in six months.

The camera system could also be done for a couple hundred dollars, but I'm less confident in the benefit...might need to take a chance on removing the mirrors for a tank to see what effect that has (with me driving it, not her).

Just because its a Jeep doesnt mean it cant be more efficient. We are limited in how much gains can be had, certainly, but there are gains out there.
How many times have people thought about headers for this same reason? How many people use a road-oriented tire with a low rolling resistance? How many people remove the spare tire for weight reduction while driving around town? How about pulling the hood insulation? The "balls" by the rear diff? Has weight ever been a consideration in choosing new wheels? Lower temp t-stat? Aftermarket exhaust?

 

[tjkj2002]

How about replacing the side view mirrors with cameras? How about an air dam in front of the wipers to smooth out the transition between the hood and windshield?

If the vehicle came with side mirrors it must retain side mirrors,it's the law and the KJ requires 2 side mirrors.They also make those cowl things you talk about but interfere with the windshield wiper operation and is not a good idea if you live in a place that gets snow.

 

[Ry' N Jen]

By the time you add up all the costs of additional
equipment, materials/supplies, and labour and or extra
tools...
Whatever floats your boat!
I hope for your sake it pays off for you.
I doubt it will! (And many others here probably
feel the same way as I do!)
Just don't ruin your daughters KJ in the process!