[mattW]

Just wondering what people have done to improve the aerodynamics of their vehicles; belly pans, body kits, fiberglassing (Please elaberate). And whether or not these changes have made a noticible difference to range/performance.

 

[Coley]

Nothing really, as I only run around, under 40 mph.

Might consider a sleeker body next time.

 

[KiwiEV]

Me too. My MitsuBrickshi will be a town-only car with the option of highway speed so aerodynamics aren't an issue.
This is a good thing too as I don't know where I'd get the money to sleek-en my car. It's about as aerodynamic as an old television. Hehehe

 

[Greenflight]

Well, my truck is kind of a total loss when it comes to aerodynamics... I did add a homemade bed cover, which should help a little bit. Just a couple days ago, I also lowered the front a few inches, which is more of a looks thing but may also help with aerodynamics.

My Tercel is a fairly sleek car as is, but I'll probably add some body work to it once I get it going. May put a belly pan on it. We'll see.

 

[Mr. Sharkey]

I'm not sure how useful a poll is going to be unless it's yes/no, as there are many components to enhancing aerodynamics that would make for a very convoluted poll tally.

In my case, I installed the factory GTI air dam and wheel arch flares, which are purported to lower the Cd by .4 alone. My car also has the grille blocked off by plastic inserts, and I replaced the open vents behind the front bumper with factory blanks. I've installed later model bumper mounts on the front that move the bumper closer to the body, and installed a factory valance between the bumper and the bottom of the grille which closes off the gap, lowering air circulation in that area.

Since the Pusher needs cooling air to enter the grille, I've fabricated custom mounts and cut down the rear air deflector from a 1980's Oldsmobile station wagon to catch a bit of the air coming off the rear of the roof and direct it down the slope of the rear hatch. No scientific data on that modification, but anything that smooths the air flow behind the car can't be bad.

Once, when this topic came up on the EVDL, it was suggested that installing factory fender liners from a Cabriolet could help reduce turbulence inside the wheel wells. I've obtained a set, but not yet installed them.

If I haven't already posted it here somewhere else, here's one possibility for improving front aerodynamics:

Looks a bit like Darth Vader or Dick Cheney, but it's cheap (foam insulation panels, duct tape and drywall screws), and it retains all of the factory safety equipment associated with the shock absorbing bumper, etc.

Finally, doing some research on a well-established platform might allow one to dig up images such as these:

You'll note that the Golf model involved is a European model, with the small metal bumpers and a "duckbill" spoiler under the front lip. It would be interesting to comare this with a typical U.S. issue DOT-approved shock absorber type bumper and no spoiler and/or a GTI set...

 

[mattW]

Hey sharkey,
Nice post! Yeah the poll was just to get an idea of how far people were willing to go, and to spark some discussion on the topic. I think its general enough not to get too complex and you can select more than one option. You've done some nice work on your rabbit, have you got any photos of the rear air deflector? I don't know how much that darth vader body kit will do for EV PR... that thing is huge! And i doubt it would be as effective as just a nice rounded front like the EV1 or a streamliner. You want your car to be as close to a tear drop shape as possible. There is a nice quick outline of what the insight designers did for aerodynamics at http://www.insightcentral.net/encyclopedia/enaero.html

 

[Mr. Sharkey]

Although the deflector is visible on several photos I have of the car, none show it very well. I drove the car today for the first time in six months, an afternoon jaunt into town to meet my sister and brother-in-law for coffee. I took the camera along to catch a shot of the car and the deflector, but it got late, and after a double shot of espresso, I was absolutely frying and couldn't stand still long enough to pull the car over at some picturesque location and frame up a photo. For that matter, I'm still buzzing from the caffeine five hours later...

Maybe tomorrow...

In the meantime, here's a shot of the tucked-in front bumper, trim valance, custom headlight guards and the GTI spoiler, just visible at the bottom...

 

[veperformance]

i dont think it will make a big difference but i will install lexan cover in front of the fog lamp area and cover underneat , that shoud give me good aerodynamic and protec the motor and electronics.(i tryed to attache a picture but i'm not shure it worked.)

 

[Greenflight]

OK, I got to take my truck for a test drive with the front lowered. I didn't notice much difference below 30, but I think I picked up about 3-4 mph in third gear.

Oh yeah, that was a good post Sharkey!

 

[Mr. Sharkey]

Don't know if anyone is still interested, but I did say that I'd post some pics of the rear deflector.

Here it is in a side view. I had my sheet metal guy fabricate some sheet aluminum brackets that fold under the hatch so that I didn't have to drill any holes on the exterior of the hatch:

(this view is of two Rabbits sitting side-by-side, the one in the foreground is powered by Biodiesel)

I didn't want a Rice-Racer picnic table sized fake wing apperance, so I made sure that it was pretty much tucked into the roofline of the car, and directed the airflow down over the hatch.

From the rear:

The Oldsmobile deflector ($10 at a wrecking yard) was much too wide for the VW, so I put it through the band saw, sculpting the ends to compliment the countours of the top of the roof at the sides. In this view, it looks fairly wide, but when you stand back a bit, it blends into the natural lines of the car.

A few holes to fill with Bondo, and a can of VW-matched touch up paint, some stainess steel fasteners, and I can at least pretend that it fills in some of the vacuum created behind a moving vehicle. Next time I have the backyard wind tunnel fired up, maybe I'll run some diagnostics...

 

[John]

Since I plan on using my vehicle for a work commute most of my driving will be at 100 km/h. Aerodynamics will have a significant impact on the range of the vehicle. Whatever I do needs to be light weight as my vehicle will also be a bit weight challenged and operating quite close to it's GVWR. I'm considering degrilling the front (no point in all that cooling drag without an ICE), fitting a belly pan just under the engine (motor) compartment, fitting skirts to the rear wheel arches and turbulators over the rear window. I will try to verify each aero mod as an improvement somehow such as steady state motor amps on a known piece of road in calm conditions. The function of the turbulators could be verified by taping a ribbon to the roof of the car and driving down the road with a chase car to monitor the behaviour of the ribbon. A full belly pan would certainly help the aerodynamics but would weigh quite a bit.

 

[mattW]

Check out this pick-up, sounds like its had the kind of treatment you are envisaging (except i don't know what turbulators are):

The owner says he got 28% better fuel economy for his efforts (story at http://www.evworld.com/article.cfm?storyid=870) so it sounds like its definately worth it. If it were an EV with a 40 mile (60km) range it would go up to 51 miles (82kms). I don't think you would get such a drastic change with a car but it shows you the difference aerodynamics can make.

 

[mattW]

Well this is getting interesting, i've been reading more on aerodynamics at http://autospeed.com/cms/A_2455/article.html (really great article) and found this table:

As you can see the biggest factor affecting aerodynamics for this car (a volvo under development) is the cooling package! In an electric car (depending on the motor and controller) this is almost completely unnecessary since the motors are so much more effecient. By just blocking off the majority of the airflow into the engine with a nice rounded curve you could decrease drag by a third! That and the other aerodynamic adjustments discussed earlier i think would make a pretty reasonable increase in range. Enough to be worth the effort anyways.

 

[veperformance]

Yep , front cooling trap do pick up lots of air , ev1 did quite a good job for that and thats one the reason i like my donor car.

 

[mattW]

Since the Pusher needs cooling air to enter the grille, I've fabricated custom mounts and cut down the rear air deflector from a 1980's Oldsmobile station wagon to catch a bit of the air coming off the rear of the roof and direct it down the slope of the rear hatch. No scientific data on that modification, but anything that smooths the air flow behind the car can't be bad.

Has your deflector made a noticable difference to your stability at high speed? A spoiler works by deflecting air upwards which results in a reaction force downwards on the back of the car. Your deflector is doing the opposite, deflecting air down and lifting the back up... Its possible to reduce the drag of a car but increase the lift which results in a effiecient but dangerous car. I don't mean to be critical but i don't want you spinning off the freeway at speed.

 

[Mr. Sharkey]

With 500 Kg of batteries where the back seat and fuel tank used to be, any lift generated by the deflector would be negligible.

What's laughable is all the asian import boy racers who put giant spoilers on the back of their Honda Civic and claim improvements in handling. Realistically, such attachments are eye candy only, as true aerodynamic ground effects don't really start to get generated until you are doing over 160 KpH.

In my case, the Pusher generates much more lift on the rear of the EV when it's providing power. I can and do feel the steering get a little bit lighter when I'm accelerating hard, but nothing that would cause the car to become unstable. I do have a fabulous amount of custom suspension work on the car, and it is rock solid on the road and in turns.

Oh, and high speed? "High speed" for this car is 100 KpH. If I was worried about the rear wheels coming off the ground due to the few pounds of lift that the deflector might generate, I'd put a couple of bricks in the boot.

 

[mattW]

How good are E-meters and that kind of thing at measuring your effeciency? (i was going to say fuel economy but i guess it would be amp economy ). Or i guess the bigger question is; if i was making aerodynamic changes what would be the best (electrical) diagnostic tools to test their effectiveness. You would obviously want to do before and after trips on the same stretches of road at the same speed but what/how would you measure to tell the difference?

 

[veperformance]

It is quite easy to mesure , you must run at 55mph for about 1 minute on a wide straight and leveled road and note voltage and amps every 15 seconds.you must also make shure there is no trafic close to you in any direction and make shure that tire pressure is maintained.with 4 mesures you can make an average that should be a good indication of the influence of the aerodynamic modifications. also when making your average convert your mesurements in watts ( volts * amps =watts).when your done can you post your results i'm looking forward to see them.

 

[mattW]

Well it might be a while yet, i'm still in the research/learning/saving phase of EV construction but judging by the success of other people's aerodynamic adjustments i am definately planning to do some changes and will also try to post the before and after stats. If all goes to plan i should be starting with a honda CRX. Depending on how ambititious i am at the time i intend to work on the undercar airflow with an ABS plastic belly pan (similar to http://www.autospeed.com/cms/A_2456/article.html but bumper to bumper) possibly larger wheel guards or even rear wheel covers (aka insight) and maybe even a custom fiberglass bodykit that smooths out the front air intake and bumper (using the same method as http://www.geocities.com/silverkit98/BodyKit1.html but looking more ev1-like than street racer). These will obviously be the finishing touches to the car and may or may not happen but a big part of the appeal of electric cars for me is their efficiency and so things like aerodynamics and weight reduction really appeal to me.

 

[Mr. Sharkey]

How good are E-meters and that kind of thing at measuring your effeciency?

The E-Meter patent was purchased by Xantrex and has been renamed "Link 10" (Here's a link to a descriptive page about it from Energy Outfitters). If you were to use the method described by veperformance above, the Link 10 could be very useful, especially if you purchased it with the RS232 option, which provides a data port from which you can compile data at one second intervals. Running this data through Excel, it's possible to make some very useful graphs:

Chart of power usage while using the Pusher trailer: Following the blue line, we see significant discharge currents at the beginning of the trip, which represents surface street driving and acceleration when entering the Interstate highway. About 09:25, the Pusher trailer assumed the majority of the load while operating at a steady speed on the highway, and some amount of regenerative braking replenishes the power used earlier. Large upward spikes in this line of the chart represent regenerative braking used to decelerate the vehicle at stop signals and when exiting freeway off ramps. At 09:52, I exited the freeway and drove the remainder of the trip on rural roads with some traffic stops along the way.

This chart represents about 50 miles of driving. Note that the number of ampere-hours consumed from the battery pack (yellow line) totals about -20Ah.

You could generate similar charts while running a known course at a fixed speed and see the results of any changes you make fairly easily. A one second capture duration for the data would help insure accuracy. I'm no Excel whiz, but I'm sure the program is capable of some powerful equation processing that could average the data, making the results even more useful.

I've always monitored efficiency by reading from a dedicated kilowatt hour meter and writing down the number of kilowatt hours consumed by the car and cross referencing that to the miles covered. While not an instantaneous result of efficiency, and subject to many variables, over the course of several weeks or months, a very reliable result can be obtained.

Overall,the Link 10/E-Meter is very useful. I own three of them, and wouldn't run my car or my renewable energy power systems without them, or something similar.