Aerodynamic Mods to Reduce Drag

[NeilBlanchard]

Have you done any aerodynamic modifications to lower the drag, and if so, what sort of results have you seen?

In particular, things like smooth and flat wheel covers, a smooth belly pan (full or partial), adding a Kamm back, adding rear wheel skirts, or swapping out the wiper blades with the low profile blades. If you are more adventurous, you could install video mirrors in place of the side view optical mirrors.

The benefits of these sorts of modifications will be longer range - and if you learn to coast farther with your lower drag car, then you can get a lot more range.

 

[Zelenec]

I don't really believe mentioned mods would help to extend range for more then 5% when driving slow. If you estimate financial benefit, all costs of modifications would perhaps never return.... and the car would look ridiculous.

If you really want to do something to extend range, you need range extender, like this one. It's in real life testing phase now.

 

[RobbW]

Where can we get more information on that battery range extender?

 

[Don]

I don't really believe mentioned mods would help to extend range for more then 5% when driving slow. If you estimate financial benefit, all costs of modifications would perhaps never return.... and the car would look ridiculous.

I agree

For us, the car is an around town grocery-getter. It has a horrible Cd because it's practical for what it was designed to do, and it's utility is worth 5% or even 10% off the maximum range to me any day - We hauled about 250 pounds of landscaping stones home in it from Lowes yesterday. Forget the 'range extending' Cd mods . . . . gimme a trailer hitch!! :lol:

Don

 

[NeilBlanchard]

Even at 28-30MPH about HALF the load on the drivetrain is from aerodynamic drag. And that is why lowering the drag will extend the range.

You get much more from the car you have by modifying it. All the mods I mentioned are small money, except the video mirrors. Don't knock it until you've tried it.

 

[fjpod]

Love the idea of that battery pack, but I do not usually drive more than 20 miles per day, so it would be a waste to carry around that extra weight.

It would be nice to have on days when I need it though.

 

[RobbW]

You get much more from the car you have by modifying it. All the mods I mentioned are small money, except the video mirrors. Don't knock it until you've tried it.

Neil, would you be able to quantify "much more"? If we're talking a 50% or more increase in range, then you've got my attention. But it also depends on what we have to do to extend our range that much. The problem is that to really extend your range in any significant manner, you have to incorporate several of the mods you mention. If there were one or two mods that could be performed quickly, easily, at low cost, AND significantly extend range, more people would probably be willing to look into them.

Unfortunately, most of the mods I have read about only have a minimal impact on mileage. So you have to incorporate several of them to start seeing any noticeable benefit. And as was mentioned earlier, most of them make your car look plain silly! A lot of these mods, therefore, are only pursued by tinkerers who get geeked out over a 3-5% increase in range. Or hypermilers who are obsessed with eeking out a couple more miles per charge.

Like I said, I would gladly perform mods to my car if they were easy, low cost, and didn't make my car look like a Frankenstein-monster spaceship! I'm fine with adjusting tire pressure, coasting in neutral, adjusting my driving style for slower, smoother acceleration/deceleration, etc. Heck, I would even change my windshield wipers if it makes any difference. However, I'm not likely to add rear wheel skirts, a Kamm back, a belly pan, or replace my side-view mirrors with video cameras (is that even legal?). And I'm certainly not going to drive at half the posted speed limit. I would get killed around here if I did that!

So, are there one or two mods (or even three) that I can perform that won't make me look like a nerd, won't get me beaten up, won't cause traffic jams, won't cost an arm and a leg, are easy to implement, AND will result in TRULY SIGNIFICANT range extension? If so, sign me up! I've already increased my tire pressure and have adjusted my driving style (well, except for driving ungodly slow all the time). What else is there?

 

[Don]

Even at 28-30MPH about HALF the load on the drivetrain is from aerodynamic drag. And that is why lowering the drag will extend the range.

Using the published Cd of 0.35 and your frontal area calculation of 24 sq feet, our aero drag at 25 mph calculates to a 0.9 Hp loss. If we could somehow cut the Cd down to 0.30 (which is actually pretty hard to do I understand . . . . the Leaf is a much 'slicker' package than ours and it's Cd is 0.28) the Hp loss would only be reduced to 0.7 Hp

Since 745 watts is one Hp, the 0.2 Hp we would save works out to about 150 watts. I can easily save that amount by turning off the headlights . . . . or turning down the A/C fan one click

Granted, at 50 mph that 0.2 Hp becomes a 1.6 Hp loss which is nothing to sneeze at, but it also demonstrates that cutting your speed in half will reduce the drag by 7/8ths . . . . a much, much greater reduction than making small changes to the Cd, and even small changes are hard to come by - So, my big 'range extending' trick is to drive as little as possible at 50 mph and as much as possible at 25 mph :mrgreen: Even if it means taking a slightly longer route, there is a huge savings to be had just by driving slower

I wasn't aware that any manufacturer has got a set of video mirrors through the Fed certification process as yet, or have they? I know many car manufacturers have been putting them on concept cars for quite some time, but I wasn't aware any had been cleared for road useage in the USA so far - Correct me if I'm mistaken

Don

 

[Zelenec]

Range extender are two boxes (65kg together) that are placed and connected to a trunk, if needed. When you don't need RE, it can be easily taken out.

1. box: Charger and BMS
2. box: 10 kWh battery pack

Both batteries (main and added one) can be charged at the same time from two outlets.

That's all I know for now. All additional infos will be available on earlier mentioned site.

I hope I will have a chance to test it soon.

 

[NeilBlanchard]

My brother and my father each drive i MiEV's so maybe one (or) both of them will try some mods?

I drive a Scion xA which has a stock Cd of 0.31. I used to average ~370 miles on a tank, but now I average ~490 miles. And I have had a handful of tanks well over 600 miles.

So that is roughly 32% more range on average.

 

[Zelenec]

I used to average ~370 miles on a tank, but now I average ~490 miles.

And what mods are made on your car to achieve such improvement?

 

[Zelenec]

We all love tall figure of I-miev. Easy to enter and easy do get out of the car. Such commodity goes not hand by hand with good aerodynamics. Solution is: Total Makeover of your I

Neil, you can do some tests yourself. Put your car twice on same place on short (for ex. 20m) downhill road wich continues horizontaly or slightly uphill and then coast few times in N position with your car as it is. Mark the points where it stops. Then remove or at least fold both side mirrors, do other cheap mods and try again few times. Do both tests in calm weather with no wind. If your average stop point goes much further, then you are right. Othervise...

 

[RobbW]

My brother and my father each drive i MiEV's so maybe one (or) both of them will try some mods?

I drive a Scion xA which has a stock Cd of 0.31. I used to average ~370 miles on a tank, but now I average ~490 miles. And I have had a handful of tanks well over 600 miles.

So that is roughly 32% more range on average.

I'll agree. Increasing your range 32% (extra 120 miles in your case) is nothing to scoff at, but would only add an extra 20 or so miles onto the i-MiEV. How many and which mods did you implement to extend that range? Do you have photos of your Scion with all the mods you used to get that range? Did you use extreme driving styles to get that range? How was your driving style accepted by your fellow motorists?

 

[jray3]

Zelenec- love that boost pack, please post all the detail you can. Unfortunately, Enginer went out of business rather than improve their quality, and I'm not aware of anyone putting a Hymotion kit or similar into their EV...

Regarding aero mods. I added an 18" lexan 'duckbill' to my rear hatch and swear it reduced wind noise. Didn't get any coastdown testing done before removing it for my trade-in. Also used full moon wheel covers, but they made a crinkling sound, and I prefer the ultralight alloys that came with my SE.

Don, I'm assuming that you got the Torklift Ecohitch? http://torkliftcentral.com/ecohitch/mitsubishi/ecohitch_miev.php
I have a lot of fun with mine, and carried a very bulky VW subframe on the highway for 3 hours with a cargo platform (though the hitch is still a heavy beast even after drilling out nearly 10 lbs)...

I sometimes drive around with a beat-up and greasy 2 5/16" ball hitch mounted, just to enjoy the double-takes from other drivers. :roll:

 

[NeilBlanchard]

I certainly do have a bunch of pictures and an extensive build thread over at EcoModder.com:

http://ecomodder.com/forum/showthread.php/scion-xa-aero-mods-2969.html

I was on Chronicle a while back:

http://www.wcvb.com/chronicle/Beating-gas-pains/-/12523032/14865358/-/xnrewx/-/index.html
http://www.wcvb.com/chronicle/Driving-alternatives/-/12523032/14865454/-/ctcrfwz/-/index.html
http://www.wcvb.com/chronicle/Secrets-of-the-hypermilers/-/12523032/14865532/-/6r2wryz/-/index.html

Here's my Photobucket library:

http://smg.photobucket.com/user/NeilBlanchard/media/Scion xA AeroMods/DSC_7480.jpg.html?sort=3&o=0

I've have done a coastdown test, using the Instructables procedure and spreadsheet - I *think* that the modified Cd is ~0.26-0.27-ish. I always intended to remake all the "temporary" Coroplast and tape "experiments" with aluminum and fiberglass - and I have done some of these. The video cameras are by far the most expensive pieces - probably about ~$200 or so. The Coroplast 4x8 sheet was $20, and I'm sure I've used at least $50 worth of tape and tape adhesive remover has been $20 or so.

Remember, I don't have a belly pan (any more) and my gearing is *horrible*. And the 32% estimate is a year round average. Aero drag is significantly worse in the winter - cold air is much denser; adding about 6% drag at 30F vs 65F. My actual fuel economy is about 40-75% higher than the EPA Combined estimate. If you can achieve a 70% increase, that is about 107 mile range.

You will also need to use full ecodriving techniques - better coasting won't help as much unless you take full advantage by coasting in neutral, and reducing how much you accelerate, etc. With an EV, you have huge advantages over my car: no idling, nearly peak efficiency most of the time, regen braking, reduced cooling needs, no warm up time, etc.

 

[Llecentaur]

Hi Neil,

Don't you think that the most interesting mod would be to build a removable, even foldable rear "triangle" that we could fix with high strength suction cups onto the rear mirror and body?

I would imagine it in plexiglas to allow visibility and stop light to be effective.

Maybe also something similar for the front wiper and front spoiler without going as extreme as the Honda we saw in the video

 

[siai47]

If you want to really lower the aerodynamic drag on the I-MiEV, take all the powertrain components out of it and put them in a original style Honda Insight---now you would have something with a low CD. The only real difficulty would be to convert the Insight to rear drive or face a wiring nightmare trying to put the motor in the front. It would be a fun project and give you a really neat car.

 

[PV1]

For those lucky enough, take the drivetrain and two MiEV batteries and put it in an EV1. A 1,200 lb. super slick shell with a 32 kWh lithium battery would easily give you 130+ miles of 45 mph+ driving, if you were allowed to put an EV1 on the road (thanks GM). So, for everyone else except that handful of people with access to one, the original Insight would be your best bet.

Packaging would be fairly easy, since the original wiring from the battery to the controller, then to the motor could remain with the controller and charger staying above the drivetrain.

 

[NeilBlanchard]

I think the EV1 with a 32kWh lithium pack would be well in excess of 200 miles range. The Illuminati Motors 'Seven' went over 215 miles on a 33kWh lithium pack, and Dave Cloud's Dolphin went over 200 miles with a ~32kWh LEAD ACID pack.

 

[RobbW]

Just an interesting side note regarding aerodynamic mods (not related to i-MiEV). Over the Labor Day weekend, the family and I went up to Traverse City, MI (6.5 drive). Along the way, both to and from, we saw many semi trailers with these "Trailer Tail" attachments on the backs of the trailers.