# Pickup truck Aerodynamics



## rankhornjp (Nov 26, 2007)

they did this on Mythbusters and by their experiment the "net" was the best for fuel mileage.


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## david85 (Nov 12, 2007)

As I recall, the gain of economy was within the margin of error compared to running with the stock tailgate up. I think that was that the re-visit on the tailgate myth???

I have two fullsize pickups, and I can tell you that a canopy does NOT help lol. but the best MPG I ever got was in my F250 diesel, running with the tailgate up, and an empty box (22MPG @ 70MPH).

A belly pan would make a difference with a pickup, because there are large pockets created by the chassis, bulky axles and exposed suspension, but Its going to take some figuring out. reducing ground clearence would also help.


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## BenNelson (Jul 27, 2007)

Has anyone done a belly pan or other aerodynamics with Coroplast? (corregated plastic)

Seems like it would be the material of choice - Light/rustproof. Can't be too expensive either, I wouldn't think.

There is a guy who put a big pointy tail on the back of his Honda Civic, and it gets almost 100 mpg because of it. That was all Coroplast.


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## david85 (Nov 12, 2007)

I made some small dirt shields on on truck once to keep gravel and road salt from getting into tight places in the body once. That was 5 years ago and they are both still there. really can't beat the price, and at the very least you can have a good test without spending too much. The only real weakness of coroplast is UV light.


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## mattyd (Jan 8, 2008)

There is a guy somewhere online who took a 2wd ute (small truck with a tray) and made a sloping canopy that went straight from the roof line down to the top of the gate. You could do something like that, and use that plastic and plexiglass stuff to make it see through, and get a nice aerodynamic shape happening.


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## mattW (Sep 14, 2007)

Here is an example of pick-up aero-modding:








There is an article about it on EV World. Also try the Aerodynamics topic on the wiki and look at projects. A belly pan will make a big difference because you have substantial ground clearance but a sloping rear cover will have the most profound effect. The ideal angle is around 10-11 degrees to minimise drag and lift. If you look at the following table under the 'A' it shows both the Drag and lift associated with differing rear slope angles. At somewhere around 30 degrees the air separates completely which is why the curve is not continuous:


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## david85 (Nov 12, 2007)

> The intersting thing here was the belly pan which improved the mileage to 28% percent over the 11% improvement with just the aeroshell alone


Borrowed from some of the comments of the article.

This REALLY makes me wonder! My truck is capable of more than 22 MPG as I have since replaced the 3 speed with a 4 speed (overdrive) tranny. It has all the aerodynamics of a brick, but maybe a bellypan is worth considering, I'll have to crawl under it tomorow to have a look.

From the research mythbusters did, you can see that a bubble forms in the box that streamlines air flow over the box almost like the aeroshell, but no such effect can happen under the truck without mods.


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## piotrsko (Dec 9, 2007)

my $.02 based on my experiments with my truck: f 250 cc longbed

fuel mileage went up 10% for every inch of drop in vehicle height (limit was 4 inches due to suspension, and no I didn't end up with 40% better mileage) this supports the belly pan theory

mileage went down with every inch raised by 10%

rounded rear cab high camper shell gave me almost 20% better. I'm thinking the mythbuster data was only good for their style of vehicle

!! suprise!! a camper shell inflatable boot between the bed and cab gave me 5% improvement

Load range "F" tires @ 90 psi was good for another 5%

8000 lb truck gets 22/25 mpg on CA wierd smog fuel.


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## david85 (Nov 12, 2007)

piotrsko said:


> my $.02 based on my experiments with my truck: f 250 cc longbed
> 
> fuel mileage went up 10% for every inch of drop in vehicle height (limit was 4 inches due to suspension, and no I didn't end up with 40% better mileage) this supports the belly pan theory
> 
> ...


 
Nicely done! The mythbusters test vehicle was a F150 crew cab with a short box, so your truck will behave differently. What was your cruise speed? Was th etruck 4x4 to begin with?


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## piotrsko (Dec 9, 2007)

oops, sorry didn't do the speed thing here as I believed it wasn't applicable to plain areodynamics. It is also a 2X4 because the 4wd costs about 15% in mileage losses, possibly due to gearing, and ride height increases.

however; where the torque curve crosses the HP curve is the optimum speed for IC engine efficiency. in mine it is 1750 rpm or 59 mph (it's a diesel). In another experimentation process, I ran at 59 on the freeway for about 300 miles and got the mileage up to 26. I also decided that 59 was a hazardous speed even in the extreme right hand lane. at 65 mpg falls off to 22 and at 70 it falls to 18. 70 mph is way outside the peak torque curve and the induced drag bucket is getting huge.

Generally when i do the mpg testing I run at 65 (safer speed), but with the cruise control on. CC costs me some efficiency, but the data is somewhat more linear.


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## david85 (Nov 12, 2007)

Sounds like your truck is close to mine. I've got 1986 F250 Ex cab 2wd 6.9L diesel. Originally came with C6 auto, and 4.10 gears, and it really slurped the fuel! I was able to find aftermarket 3.08 gears, and later installed an E4OD. I also modified the cruise control to be only capable of giving enough power to hold about 70-75 MPH. that way it would automatically allow speed to bleed off on a short hill ahd slowly accellerate back up to speed. While towing, I would set the speed to 75, and the truck could only do 70, the advantage is the truck automatically picks up some speed going downhill, and bleads off while going uphill, keeping the overall fuel rate down.

I don't have any tests below 70 MPH average speed, as you said, it can get hairy when you don't match the posted speed (and everyone else is at least 10 over the limit). 

What year is your truck?


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## BenNelson (Jul 27, 2007)

It's a 1995 Chevy S10 pickup with a 2.2L engine and 5 speed manual transmission. 100,000 miles on it.

I just bought it last week as a utility vehicle for hauling firewood, pulling my little camping trailer, and having something to run to the auto parts store to fix my car.

Yesterday, I put fuel in it for the first time, and calculated 22 MPG on it. I was really expecting around 26.

I haven't done anything to it yet, I still need to check the air and fuel filters. Not sure when other "regular maintenance" things I should be doing for max fuel econmomy.


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## piotrsko (Dec 9, 2007)

'00 with a 6 spd and 3.73 gears, but i think we are starting to get off topic here


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## david85 (Nov 12, 2007)

piotrsko said:


> '00 with a 6 spd and 3.73 gears, but i think we are starting to get off topic here


The reason I asked, is I was trying to figure out how you dropped the front end, my truck uses TTB front suspension and cannot be lowered without throwing wheel camber off /-\.

BenNelson, what is your cruise speed when you got 22 MPG? Recheck the numbers everytime you fill up, and average them, you might have an outliner calculation.

Regular maintainence is the first thing I would do, not sure how much work you want to put into the ICE, but there are a few tricks that might help with MPG. Your front end suspension should allow you to drop the front end, and I would even expect there to be a lowering kit available for the S10.


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## BenNelson (Jul 27, 2007)

I think I would eventually like to lower the truck, put on a belly pan, and a few other minor modifications.

I bought the truck for use with the ICE with the dream of converting it over to electric. Not sure if that will actually ever happen with this truck or not, but it should be a good vehicle for doing some experimenting on.

I have also been on the Ecomodder.com web forum lately.

That entire forum is on increasing fuel economy as hobby/economic/ecological reasons.

It does have a Fossil Fuel Free discussion area as well. I thought there is a lot of useful information on there that applies to electric vehicles as well.

Here is a thread about an interesting aerodynamic pickup truck cap:http://ecomodder.com/forum/showthread.php?t=583


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## MitchJi (Dec 14, 2007)

Hi,

Simple, easy DIY Belly Pan here (click on "Belly pan, Wheel covers, Door locks)":
http://www.metricmind.com/ac_honda/main2.htm

Best Wishes ,

Mitch


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## ngrimm (Oct 19, 2007)

I wonder how much effect a properly designed air dam would have on these trucks. The reason I mention that is I used to be into Datsun Z cars and was reading about the coefficient of drag for various cars. It seems that looks can be quite deceiving when it comes to body styles. For instance I always figured the 240-280z cars would be great but according to the racing gurus (salt flat guys) on zcar.com they are terrible. In fact they are no better than an old VW bus. In stock form there is so much lift at speeds over 100 mph they can blow right off the road. And the drag is such that it takes an great deal of power to increase the speed a few mph. The 280zx on the other hand was designed with the aid of a wind tunnel and so it doesn't have the same problems and some air dams and rear spoilers have been designed to help the older ones as well. I kinda miss my 280zx turbo. Cheers! Norm


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## the slashmaster (Feb 24, 2008)

BenNelson said:


> Can anyone tell me what the best way to gain fuel economy on a pickup truck is by improving aerodynamics?
> 
> The typical ways I can think of are:
> Cap
> ...


I don't know how much this is worth but I know you can buy a radio antenna that you stick around the inside of your windshield. That should help. Doesn't work as well as a regular antenna but if you have a cd player who cares. If your willing to live without a passengers side rearview that helps too.


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## Slow_S10 (Mar 18, 2008)

BenNelson said:


> Can anyone tell me what the best way to gain fuel economy on a pickup truck is by improving aerodynamics?
> 
> The typical ways I can think of are:
> Cap
> ...


I actually have basically the same truck, mine is a 98 regular cab 4cyl 5spd S10. A few things I have done to improve the aerodynamics of my truck include; lowering the ride height about 4 inches, Installing a hard tonneau cover on the bed, Installing smaller "Sport" mirrors, and installing a diffrent style grill that limits more of the airflow into the engine bay. Aside from the Aero mods I have also installed a K&N intake and a custom free flowing exhaust. 

On average I achieve about 26 to 28 MPG with mixed but mostly interstate driving. I plan on in the near future switching over to a narrower tire as the truck currently has 235mm wide tires, and also removing the antenna mast.

I do not have any plans to convert this truck over to electricity any time soon but I do have a thorough knowledge of Civics and CRXs' and I hope to convert one of those in the near future to use as a commuter car.


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## MitchJi (Dec 14, 2007)

Hi,

Check here (brief excerpts below):
http://www.evworld.com/article.cfm?archive=1&storyid=870&first=3025&end=3024


> Phil Knox's streamlined 1994 Toyota Tacoma pickup saw its fuel economy go from 25 mpg to 32 mpg at 70 mph just by improving its aerodynamics, reducing its Cd from 0.44 to 0.25, the same as the Honda Insight gasoline-electric hybrid.
> 
> Using the principles of aerodynamics, Phil Knox's recent additions of an aero-shell, under-belly pan, rear wheel skirts, wheel covers and grill block to his 1994 T-100 Toyota pickup improved his gas mileage by 28 percent over the original highway mileage.


Best Wishes,

Mitch


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## helixev (Nov 7, 2007)

What speed does drag start to really be an issue? If I never really go over 45-50mph would it be worth doing some aero mods to my truck like a belly pan and slopped cap?


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## MrCrabs (Mar 7, 2008)

I was playing with the EV calculator, and it seems like from 0-25 mph air resistance is fairly linear, however at those speeds Rolling resistance is a bigger factor.
Once you get above 30 air drag starts growing exponentially.. So if you drive at 45 alot, you might benefit from some areo-mods


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## Thalass (Dec 28, 2007)

I really recommend the Ecomodder.com forums. They have a whole forum devoted to aerodynamics. 

From what I've gleaned, a belly pan is quite effective, as well as mirror deletes and general smoothing of the body shape. I'm going to have to do a bit of studying for my brumby conversion.


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