Improving Vehicle Efficiencies -- A List!

[Neil Blanchard]

I want to try to list steps that car makers, and drivers could/should take to improve the efficiency of their vehicles, in approximate order of cost:

EcoDriving involves moderation: top speed should be reduced, use only as much throttle as needed (try to not need to use the brakes!), thinking ahead so you can take full advantage of downhills, minimize the use of air conditioning, trip planning for consolidation – and walking to everything that is a mile or less.

The most obvious improvement to cars, would be to mold the plastic on the front of the vehicle to be smooth and round, with grill openings that are sized (and placed) only as required to cool the motor and/or battery packs. Some new plastic bumper covers and grill pieces could be snapped onto cars. Flush covers should be used on all lights. Fairing pieces could be added to side mirrors. Hood gap gaskets, and streamlined wheel covers are easy, too.

All these improvements (above) can add at least 10% and as much as 25% to the fuel economy. Here's more:

* Sealing all the seams and joints (with gaskets or backing flanges) in the high pressure areas of the vehicle.

* Smooth floor pans with no sharp protrusions -- this is part of the drag just as much as the parts of the car that can be easily seen. Smoothing the underside with covers (like the EV-1).

* Narrower and lighter, LRR (low rolling resistance) tires should be used.

* Average & "instant" mileage displays, that are on all the time. The new Honda Insight, the 3rd gen Prius, and some Ford models, have excellent displays that help the driver be more efficient.

* Throttle control (rather than cruise/speed control!) that maintains even throttle in a user-set speed range, with minimal throttle increases to maintain the speed in that range.

* Tire pressure monitor, that warns the driver when the tires get below the recommended pressure (which could be adjusted upwards if the driver wants to run a pressure up to the tire sidewall maximum). Or better yet:fill tires with foam,so they would never deflate, and minimize rolling resistance.

* Efficient and effective fresh air flow through the vehicle, with intakes on a high pressure area, and exhaust vent(s) out the back of the vehicle into the low pressure wake zone, to reduce drag as much as possible.

* Coat all the window glass to exclude as much heat as possible. With effective fresh air flow (see above) this may completely avoid the need for A/C (see below).

* On defrost mode, the A/C should only come on automatically at maximum defrost (if at all), and it should be on a timer of ~1 minute, and it should always be toggled on/off by the driver. I would prefer to make A/C on the defrost setting optional.

* Efficient lights such as LED's and HID, that use a little power as possible while functioning as well (or better) than incandescent lights.

* Lower consumption electronics, such as A/C, fans and audio systems. Some/all of these could be powered by solar PV panels with a robust battery system.

* Active grill, that opens when more cooling air is needed, but remains closed – and is more aerodynamic most of the time. This can also be done passively with the right airfoil shapes that effectively closes off air flow when the velocity goes up.

* Wheel alignment and brake drag needs to be minimized, easy to adjust, and robust – to maximize rolling efficiency.

* Video cameras and screens in place of side mirrors. This would help a lot with aerodynamics. An example of this starts in post #167: http://ecomodder.com/forum/showthread.php/scion-xa-aero-mods-2969-1...

* Tighten up wheel openings, and always use aerodynamically designed wheels/covers, with rear wheel skirts (at least optional).

* Make roof racks removable. Years ago, I saw a "papoose" add-on storage system that locked onto the back of the car, with a single caster wheel to support the weight -- it tucked completely into the air flow behind the car; and it would be a great way to add storage space when needed; that did not affect how you drove very much. It could actually greatly improve the overall aerodynamic drag of the vehicle.

* An item that has indirect benefits: instead of thick foam and spring seats, they should be mesh or fabric stretched onto frames that provide the right ergonomic shape and provide good support without weighing so much, and taking up a lot of space. This allows a smaller and lighter vehicle because the size of car can be smaller and/or just have more room. Mesh seats would be much cooler in hot weather, and reduce/eliminate the need for A/C.

* Regenerative shock absorbers: MIT has a method of using hydraulics to drive a generator, to charge the electric drive batteries. These can also be used to lift and level the vehicle, to improve aerodynamics under different loads.

* Use a composite wheel/tire that has low weight, very low rolling resistance (by being strong enough to stay round), and low aerodynamic drag, no worries about inflation -- and re-tune the suspension to work with said wheel/tire. (see item above) This could gain even more energy, since very little would be damped by the tires.

* Multiple car door latches could be used to increase strength & safety of the chassis -- helps to further reduce weight, increase strength & rigidity, without requiring an unusual entry method (such as the VW 1 Liter car or the Loremo).

* Nissan is (supposedly) going to reduce their cars weight by ~15%. I think all cars could be reduced by 20-30% with smarter steel fabrications, smarter use of materials. Here's a site that shows a steel chassis that is 25% lighter and nearly twice as stiff/strong as a conventional steel chassis:

http://www.bluescopesteel.com.au/go/news/ultra-light-steel-auto-bod...

* Use an EV drive train, combining batteries and a supercapacitor, and a "smart" controller, that makes use of GPS and elevation data, to use the supercap for the high current regenerative charging and short(er) duration acceleration, and/or to then charge the battery at a rate that does not stress them. In other words, using the supercap as an I/O energy cache, to reduce the requirements on the battery. This can either reduce the cost of the battery, and/or increase the battery lifespan and probably increase range; especially in high traffic urban driving or in hilly conditions. Driving on flat terrain at (more or less) constant speed probably will be more dependent on the battery, and less on the supercapacitor.

* Rework the overall shape of the vehicle to reduce drag. Cd of 0.16-0.25 are achievable! The 1937 Schlör “Pillbug” seats 5-7 people and has a Cd of 0.13 – this car should used a model! (See picture above!) Also, the early model of the Mercedes “Bionic” car (aka the “Boxfish”) had a Cd of just 0.095 (the later Bionic car was still excellent at 0.19) would also be a great place to start.

Is there anything that I left out? Check out my personal blog for more...

[Dan Frederiksen]

ah ok, the dynamics might be different for smaller models. that would certainly be an impressive Cd.

if you look at the side drawing of your car with the seating positions showing, imagine how much smaller a cross section the car would have if you raised their legs to near level.
you should add shallow seating position to your list of recommendations

[Neil Blanchard]

Here's another source with the progression of Cd's:

http://www.worldcarfans.com/10506078963/mercedes-benz-bionic-concep...

[Neil Blanchard]

Here's the highest resolution picture of the Bionic model I can find:

http://www.carbodydesign.com/archive/2008/03/01-mercedes-benz-bioni...

[Neil Blanchard]

Hi Dan,

The 0.095 is the Cd of the blue (clay?) model, with the covered wheels:

http://www.dancewithshadows.com/auto/mercedes-benz-bionic-car-galle...

The first model (no wheels, shaped like the boxfish) had a Cd of just 0.06. Then the blue model with wheels was tested with 0.095, a second blue model with open wheels (and an unknown Cd),and the "final" car (with open wheels, save the partial rear skirt) is Cd 0.19.

[Dan Frederiksen]

looks like you are using a Cd for the mercedes that's twice as good as they are claiming. they claimed 0.19. where are you getting the 0.095 value?

[Neil Blanchard]

Right -- the area of the CarBEN is under 25 sq ft (I have it drawn in DataCAD), so *if* the Cd is as low as the blue Mercedes model, the CdA would be just 2.5 sq ft! This is better than even the Aptera 2e. If the Cd is slightly worse than the EV-1 or the Bionic, then the CdA would be ~5 sq ft or less than 0.5 sq meter.

[Dan Frederiksen]

do you understand that the coefficient is cross section area independent? meaning a huge car can get Cd of 0.19.
it's the CdA you want to compare. the coefficient times the cross section area.

did you get the idea about raising the feet or do I have to draw the difference?
you design seems very tall and you have to understand is going to cost you in air drag

[Neil Blanchard]

Thanks for your comments, Dan. Here's the link to the video we are referring to:

http://www.youtube.com/watch?v=C7jbqgCvx8U

And my blog entry which discusses the design and has more photos and images:

http://neilblanchard.vox.com/library/post/carben-concept-ev-an-open...

The challenge is to get enough interior volume to seat 4-5 people, and a square-ish section is the most efficient way to enclose this. I'm basing the design on the early (blue) model of the Mercedes Bionic (aka Boxfish) car; shown in my blog entry. It has an extremely low drag, and the built version equals the EV-1 in drag coefficient. I'm planning on keeping the wheels covered (obviously) so I'm hoping to beat the EV-1 and Bionic designs. :-)

Sincerely, Neil

[Dan Frederiksen]

Shallow seating position, put your feet up, take a load off. it reduces the cross section of the car. why should your feet needlessly go straight down.., and raise the floor up to just under the shell seat, again to waste as little cross section as possible.
a beam under the door can go deeper because the wheels have already broken the airflow there. this will add strength

Fiber glass monocoque body

Composite air less narrow wheels. the lighter the vehicle the narrower rubber it can use and still have long tire life. the grip on the road is actually independent on wheel width if the material is the same. but a narrower wheel has less material to wear. but reducing the weight with the wheel width restores the balance

obviously battery electric drive.
because the car is light and efficient the battery amount can also be small as well as the range extending combustion engine. 1-2cylinders. maybe 600cc.
it could be improved by using a rocking piston on a pivot off to the side and movig in a curved chamber, this will free it from wall friction and use of lubrication. similarly the valves could be rotating cylinders instead of a camshaft rubbing down the spring loaded valves which is friction based and quite wasteful.

the electric motor can be ironfree permanent magnet. this seems to allow very low weight as well as high efficiency especially in effortless glide. ceramic bearings. no lubrication.

I would suggest you redesign your concept car with the shallow seating position and much more like the EV1, not the inflated VW minibus shape.

A123 has a new 20Ah pouch cell which has the same high power level but even higher energy density of around 145Wh/kg. that's likely a really good product for plugin hybrids or straight EVs for that matter

[Neil Blanchard]

I found some more pictures of the Schlörwagen:

Schlörwagen thread on the Aptera forum