Arerodynamics

[Worlds Fastest Comanche]

You may think I am in the wrong place to talk about areodynamics, our trucks are built like bricks. But if we could get them a little more areodynamic, maybe we could save some gas. One thing i learned at Bonneville is that the most areodynamic bed cover is half a bed cover. A cover that starts in the middle of the bed and goes towards the rear. It needs to have a verticle bulkhead from the floor to the cover. This design was used on the 1990 GMC Syclone. It came from extensive testing in the GM wind tunnel.

 

I have been trying to find out the Drag Coeifecient of my Comanche, i found a published number for a 91 Cherokee, it was .45 The Frontal area was 25.84 ft/sq or 2.4 m/sq. i don't know if drag would be the same for a Comanche. I asume the frontal area would be the same.

Maybe we can help each other out here. I found a excel program that lets you calculate the Cd (drag Coeificent) and rolling resistance of a car, you can find the spreasheet and procedure here http://www.instructables.com/id/Measure-the-drag-coefficient-of-your-car/

 

It would be interisting to get numbers for stock comanches, lifted, different tires etc. It would give us a good idea what changes we can make to save gas, and what changes not to make that will cause a large change in either Cd or rolling resistance. It would be good the do the test before making changes, then after the change to see if you made things better or worse.

[comanche12]

that or just remove ur tail gate by reduce weight plus less drag. i think

[Pete M]

that or just remove ur tail gate by reduce weight plus less drag. i think

 

 

mythbusters busted that one. :thumbsup:

[Pete M]

One thing i learned at Bonneville is that the most areodynamic bed cover is half a bed cover. A cover that starts in the middle of the bed and goes towards the rear. It needs to have a verticle bulkhead from the floor to the cover. This design was used on the 1990 GMC Syclone. It came from extensive testing in the GM wind tunnel.

 

 

so then the small vortex that forms behind the cab gives its best results when it's restricted to about 3 feet of bed room? that makes sense. It'd be about as wide as it is tall as I imagine it wants to swirl in a circle.

[beepbeepmyredjeep]

I wonder if a Jeep 2500 conversion would help with aerodynamics a little?

 

Or maybe at least try to add the front of an early model ZJ?

[beepbeepmyredjeep]

By the way, once I get the MJ back up and running again (still working on the CMC) I could possibly perform some tests with and without my bed cap. That should help I would think.

[Worlds Fastest Comanche]

that or just remove ur tail gate by reduce weight plus less drag. i think

 

Look around the internet, you can actually get worse gas miliage with the tailgate removed.

[Worlds Fastest Comanche]

 

so then the small vortex that forms behind the cab gives its best results when it's restricted to about 3 feet of bed room? that makes sense. It'd be about as wide as it is tall as I imagine it wants to swirl in a circle.

 

You broke the code, 100% correct. Somthing could probably also be done with vortex generators near the rear of the roof

[Automan2164]

That eco modder site is pretty cool. What about something like this Peter?

 

http://ecomodder.com/forum/showthread.p ... -7333.html

 

Rob L.

[HOrnbrod]

Ecocap! Even with my Leer MJ cap on, I get 3-4 more MPG on the freeway than w/o it. I suspect though that the extra weight hauling it around town eats that savings up............ :(

 

[beepbeepmyredjeep]

A word of caution with regards to the "Aerojeep".

 

Your design resembles that of an airplane wing.

 

You could actually create "lift" with this design at higher speeds.

 

See http://www.allstar.fiu.edu/aero/experiment1.htm

 

You could possibly reduce fuel efficiency at higher speeds due to less traction. Worst case scenario, you could possibly lose control of the truck due to the front wheels coming off the ground.

 

This *MIGHT* be ok for normal highway driving ~65 MPH. However, it would DEFINITELY not recommend it for LSR-3.

[Worlds Fastest Comanche]

I was reading about the design of the Cobra hardtop, the rear of the car is kind of flat, but the shape creates a bubble that acts like a tapered surface, The same idea could be applied to Pickups, we just need an expert in aerodynamics to design it,

[HOrnbrod]

A word of caution with regards to the "Aerojeep".

 

Your design resembles that of an airplane wing.

 

You could actually create "lift" with this design at higher speeds.

 

See http://www.allstar.fiu.edu/aero/experiment1.htm

 

You could possibly reduce fuel efficiency at higher speeds due to less traction. Worst case scenario, you could possibly lose control of the truck due to the front wheels coming off the ground.

 

This *MIGHT* be ok for normal highway driving ~65 MPH. However, it would DEFINITELY not recommend it for LSR-3.

 

Just curious who/what you are referring to??

[comanche12]

that or just remove ur tail gate by reduce weight plus less drag. i think

 

 

mythbusters busted that one. :thumbsup:

oh dang curse u Adam and Jamie! lol :fs2:

i gotta have miss that part :roll:

[Timmaay]

How about you dimple it like a golf ball. Start watching at about 2:20.

http://www.youtube.com/watch?v=nufXpDBELdQ

[btm24]

With my 2.5 and 5 speed, I have gotten 30 MPG on one tank (last time I filled up, actually) and I want to push it further.

 

 

 

wtf 30? i get like 10:(

[mkbruin]

:needpics:

 

need pics of bedcoverings, front mods, etc.

 

So far the only pic is a slantback F150.

[kastein]

Ecocap! Even with my Leer MJ cap on, I get 3-4 more MPG on the freeway than w/o it. I suspect though that the extra weight hauling it around town eats that savings up............ :(

 

I bet you could do pretty good with an industrial size roll of pallet wrap / "bigass saran-wrap" and some hoops. It might look like your Jeep got attacked by a spider though.

With my 2.5 and 5 speed, I have gotten 30 MPG on one tank (last time I filled up, actually) and I want to push it further.

 

 

 

wtf 30? i get like 10:(

I get 16-18 on 225s, 4.0L/AW4/3.55s in the axles doing up to 80-85mph on the highway combined with city driving, all with a heavy hammer foot. I get 23mpg on the highway if I drive like a granny 55-65mph... with 1400lbs of stuff in the back. If you gear it right, replace your air filter, replace your upstream O2 sensor, eliminate cracks and leaks in the exhaust upstream of the O2 sensor, and set your tire pressure you can get some real good gas mileage.

 

The best part? The engine and trans are (as far as I know) original equipment, never had a major overhaul, and have 227kmi on them.

 

EDIT: replace your thermostat too as noted by the last guy, 195 degree only, the 4.0 runs great when it's at 180-210 degrees or so.

[deziped]

Cheese 429 how many horses are being robbed by those big paddle mirrors hanging on your doors? Their pushing a lot of wind.

[akamcbird]

speed holes??? this can be accomplished with a riffle or a pic axe :brows:

 

 

thecheese429 awesome rims...

[Worlds Fastest Comanche]

A true representative of the Comanche Club. Make sure your sticker is still visible with the cover on.

[dakal]

how about applying the (kamm) theory to the roof line?

 

ie. extending the roof line a bit so the air moves cleaner past the cab?

[Worlds Fastest Comanche]

how about applying the (kamm) theory to the roof line?

 

ie. extending the roof line a bit so the air moves cleaner past the cab?

 

 

Good Point, you can probably get similar results by extending the roof line, putting a bulkhead halfway back in the bed, to create a swirl behind the cab, then taper from the bulkhead to the rear of the bed floor, remove the tail gate.

[fiatslug87]

Won't this shred at anything over 25 mph? Is it just 3mil plastic?

[AMCJeepMJ]

I've read this thread, then I went back and re-read it. I did not see any mention of taping joints (like hood to fender, bed to cab, etc.) and wonder if they would be of any advantage... even 1/4 of a mile/gal improvements. Maybe some plexi sheets over the headlight bezels?

 

Also coming to mind is the flow of air beneath the trucks. Comanche's aren't very pretty underneath and there's loads of pockets and ridges hiding in plain sight. Any thoughts about what can be done to assist airflow beneath?

 

Anyone consider a diffuser for the rear beneath the bed like the back of a 458 Italia or 430 Scuderia... maybe incorporated into a rollpan?