BMW Vision EfficientDynamics Concept 0.22Cd
 

Cd is the new HP again... well maybe not, but a while ago noone cared even what a car's Cd was, now the numbers are bragged about again.

BMW Vision EfficientDynamics Concept

http://www.carbodydesign.com/archive...Concept-08.jpg

what's mainly interesting in this car for me is that it's roughly a 4 door sedan shape, and that it's got good aero, no mather what will power the car of the future, good aero will always improve FE.

although the back looks as impractical as it is beautifull in a sculpture sort of way, the rest of the flowing lines, and the shape between the wheels could easily be adopted by the next generation of BMW sedans.

anyway, it's good to see some carmakers are actively looking for ways to improve a cars Cd ... the 0.3 barier has been beaten a long time ago, so not the race for a sub 0.2Cd can begin!

This is a great vehicle. Definitely interested to see what bits of this car filter down to the more plebian vehicles. (And it would be very cool if they decided to produce this one, too!)

yea at first it screams "concept car", but than when you imagine it in black...it wouldn't look that much out of place next to curent bmw's

things like the A pillars and the shape of the bonnet.

one thing that got me thinking however is that like some curent bmw's this car has an active grillblock.
What this basically means is that this car is going to have a variable Cd! it will have more air resistance with the grill open than closed and the difference could be rather big... so than how do you come up with a single Cd figure for the car?
do you take the lowest (tempting ) a 50% average or something calculated from the ammount a grill is open during a cerain test cycle?

I suspect (hope) BMW is reacting to Mercedes' claims that it will dominate production cars' Cd figures in five years:

http://ecomodder.com/forum/showthrea...ears-8284.html

I don't believe it. The sunken headlights and grill, the sculpting on the sides, the wheel flares, the taillight tunnels, all that stuff is messing with the airflow. no way is that .20. Real cool looking, tho, especially the interior, in a '50's car-of-the-future way.

Yeah, concept car. But there's a few things to like about it: lower grille block, tiny gap between fender and tire, pretty smooth wheel covers, tiny mirrors, and a body that tapers in from above, below, left, and right. Only half of those features will survive the translation from concept car, so I wouldn't expect a Cd < 0.25, which still leaves room for this car to compete with the Prius.

The powertrain is probably more impressive. When I started reading about the 1.5L, 3-cyl diesel, I rolled my eyes and said "This is not a BMW." Then I got to the part about it producing 163HP, and having 356HP and 590 ft-lbs of torque when you add in the two electric motors. Wow.

Cut all those numbers to a third, and you'd have a very reasonable Prius-fighter. Of course, it wouldn't be a BMW.

vision
 

when BMW speaks many listen,and remains a significant influence on the entire industry.The very act of including Cd in official public communications lends "significance" to aerodynamics.I'll take that as a positive.

Why cut those numbers to 1/3? What would be gained by having weaker electric motors and diesel?

All that is supposed to control airflow in a way that apparently reduces drag

it actually also reminded me of another car wich i couldn't put my finger on

the mazda taiki

perhaps not a direct visual link but there some of the same stuff going on at the back.
we all know a teardrop is a very eddicient shape, but somehow cars like the aptera do not convey a muscle car feel or sence of great "power"
also broad track 4 weeled vehicles are difficult to match with a teardorp shape
gm wen wrong there with the brutal volt concept and than had to back it of a bit.

i think the trick is to make a car wich looks powerfull and wide at the back to the eye but not to the air...

personally i think little by little the wheels are sepparating themselves from the body work... wich is ironic as it took them so long to finally become part of it

All that external layering and ducting throws me off a bit as far as low drag aero goes. They must have found ways of making the advantages of the ducts more than counteract the disadvantages. I'm kinda skeptical of ducting/layering being the best way to go though.

Which for me is a major selling point. I don't want/need a car to project an impression of power or muscle, since I can do all of that that's needed without mechanical help :-)

A 0.5L, 55HP diesel delivers better MPG than a 1.5L, 160HP diesel because it tends to operate closer to its limits, where engines are more efficient. (This car will probably require ~20HP for highway cruising.) Because it and the electric motors are smaller, they have less internal friction, and they weigh less. They can also have smaller driveshafts, fuel pumps, etc. which save weight and money throughout the car. That, plus tires, spells out the difference between a high tech, high MPG car that I would buy, and a high tech, high performance car that I wouldn't.

Are engines really more efficient at their limits, or does it just happen that engines are tuned in such a way that a small engine is more efficient than a big engine, aside from the reciprocating mass difference?

I think a 1.5L diesel could be almost as efficient if it's tuned and set up to take advantage of the hybrid electric motor assistance. For example, instead of spinning at 2000rpm on the highway, spinning at 1000rpm, since accelerating can be handled by the electrics.

not really. autospeed did a pretty good article about break speciffic fuel consumption.
every engine has a sweet spot, where it extracts the most power from the fuel it uses, usually this is at about 50% or more throttle and at low revs.
you can mostely make use from this while accelerating. because smaller engines will need more throttle for a given ammount of power they'll often opperate more within this optimal spot them bigger engines.

an engine wich can run at a constant rmp and at a constant load could be dimentioned and tuned exactly for this... and would be much more efficient them
the valve timing would be set for this exact spot, and it wouldn't even need a throttle

i found some more images about the concepts developement, with 3 images of how the air flows over the body. these are more artistic renderings but nevertheless quite interesting. theres also some picutres wich reveal the ubcerlaying structure of the car
BMW Vision EfficientDynamics: the design

Engines tend to be more efficient near their limits.

Brake Specific Fuel Consumption (BSFC) Maps - EcoModder

Pumping losses, friction, and reciprocating mass waste more energy in a larger engine, too. Downsizing the engine will improve MPG, unless it causes you to drive around at redline with your foot to the floor. See the above-linked plots. If your engine and gearbox are set up so you cruise at 2500RPM and 80% throttle, you'll do well. Though that would mean you'd have to downshift to pass, but that's worth it if it means a few more MPG.

Hello -

They'll be offering a BMW 320d in Europe that sports "EfficientDynamics" concepts :

BMW 320d EfficientDynamics Edition announced
http://img.worldcarfans.com/2009/8/medium/1842379.jpg
That's 57.37 MPG/US.

CarloSW2

Efficiency is best at lower RPM and higher loads, for normal passenger car designs.

When the effective compression (actual compression in the cylinder when combustion occurs) is highest you get the most power (without full load enrichment). Higher RPM reduces the efficiency due to reciprocation and friction losses.

Mileage would be fantastic if you could use a 20 HP engine to produce 10 HP to maintain a certain speed, but your performance would be pitiful.

The current trend is towards smaller engines that still have enough power reserve for decent performance. This is one reason forced induction may be the best solution, because it provides a reserve of power in a smaller engine.

Alfa Romeo built a Grand Prix engine in 1950 that produced 390 HP from 90 cubic inches, but it only got 2 MPG in racing trim. Modern technology allows the best of both worlds with variable valve timing and precision fuel and ignition controls and ultra high pressure fuel injection.

regards
Mech

bmw already offers "EfficientDynamics" models over here.

last weekend i saw a 1 series hatchback up close (my brother in law swapped his mpv company car with a coworker who went on holliday with it)

the underside is completely smoothly panneled as far a i could see from the front, and both grills have active grillblocks that close the grill off from behind these features are standard across the bmw line... i think some models also come with start-stop tech, wich basically shuts down the engine when you shift to neutral and let of the clutch, and restarts when you depres the clutch again

BMW EfficientDynamics : Air vent control

lunarhighway -

Well there you go. Cool. I had seen demos, but I didn't know the active grill blocks were in production.

CarloSW2

At a steady 40 MPH my 02 Insight CVT (first gen) gets 80 MPG. The 01 Echo manual would be 30MPH on the same amount of fuel, .5 GPH.

That's the same amount of fuel a 305 cubic inch V8 uses just idling. Small engines are more efficient ( in noirmal use) because they use less energy to keep their own parts moving, the Echo is .19 GPH at idle, the Insight is probably less than .15 GPH idling. Its not that small engines necessarily have better BSFC zones, its because they will always be closer to best BSFC in normal operations.

A hypermiled manual Insight would do 50 MPH (or better), on the same amount of fuel.

I love what the manufacturers are doing in Europe, and the US should have done the same a long time ago.

The Insight sat on the dealers lot for 16 months because no one would pay 20 grand for a car with such limited utility in 2002, when gas was relatively cheap.

regards
Mech

wich is exacly why start-stop technology is so valid...there's no reason why the engine should keep running when the car isn't moving i've been turning my engin on and off with the key at stoplights and it doesn't delay me at all... it's just the interface for this process that isn't convenient.

It's estimated that 13% of the fuel consumed nationwide is lost idling. Start stop should be required by law.

I think the technology is there with a toothed belt and a strong enough alternator-starter component. Maybe a larger battery for extended stops in traffic jams. You could also eliminate all the other belt driven accessories for more efficiency gains.

It could even be configured to provide a small amount of electric boost to the engine on acceleration.

regards
Mech

You swear that thing spent 5 minutes in a wind tunnel. Its a concept car AKA vaporware.