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Karma Hybrid comes with a drool worthy body and a near $100k price tag

Although many people had doubts whether Fisker's voluptuous Karma hybrid would ever make it to production, the company is making good on its promise to take on the big guns in the automotive world. To show its good faith, Fisker gave automotive publications the chance to test its first hybrid sedan.

For those that don't remember, the Karma features a turbocharged 2.0-liter Ecotec four-cylinder engine (supplied by General Motors) that develops 260hp. In addition, the Karma also features two rear-mounted 201hp electric motors (402hp total) which get their power from a 21 kWh lithium-ion battery pack. Like the current generation Prius (as an optional feature), there are solar panels in the roof to power interior accessories.

According to the previews, despite having a relatively complex and powerful 260hp engine on tap, it is only used as a generator. As a result, the Karma's electric motors are always providing the forward thrust for the vehicle.

Car and Driver:

Tugging the “sport” paddle to the left of the steering wheel brings additional energy to bear. When the gasoline engine kicks in to supplement the battery pack’s wattage—to trim the 0-to-60-mph run from a claimed 7.9 seconds to 5.9, or to add 250 miles to the driving range—the extra thrust is accompanied by the whistle of a turbo spooling up, the snarl of angry exhaust gas, and a resonant boom or two…

But the physics conspire against it keeping pace with other $100K sports sedans. In spite of the joys of low-rpm electric torque, the realities of a curb weight well above 4000 pounds and only one gear ratio mean that mileage is where this car excels. 

Inside Line:

All the exterior panels on the Karma are made of either aluminum — including the hood and outer door panels — or molded resin composite as on all four fender panels. The supersize 124.4-inch wheelbase (almost 10 inches longer than on a Porsche Panamera) is the exterior's most notable dimension and the 22-inch wheels bookend the look quite nicely... 

Our only gripe was that the Karma didn't feel as solid all around as its German and Japanese competitors. Wind noise and road noise, however, are very well contained overall. Some smaller wheels might help out in the ride quality department, too, but according to Fisker's engineers, a change in that direction would bring the center member of the steering mechanism a little too close to the ground. A set of 21-inch all-season tires is as small as they're willing to go. 

Autocar:

But the Karma has several vital factors in its favor, not least its stop-the-traffic looks, its thorough engineering, its great driving characteristics and a price that, while high, doesn’t look unrealistic against the competition. If the car makes a good start — and the 3,000 orders already held seem to promise as much — it could easily become the next must-have automobile among Hollywood’s glitterati. 

The 2012 Fisker Karma is expected to have a base price of $95,500. Conveniently, this places it in direct competition with the Porsche Panamera Hybrid S (base price $95,000). There's no question that the Karma has the Panamera beat (by far) on looks, but the Panamera has a proven family history/pedigree while the Karma is starting with a clean slate. 

With 3,000 buyers having already waiting in line to get their hands on the Karma, at least a wealthy few are willing to give the vehicle a chance.



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RE: A 260 hp gas engine?
By theapparition on 2/21/2011 10:32:34 AM , Rating: 5
Part of the performance differential comes from the heavy weight (over 4000lbs) and single gear transmission/differential/rearend (what ever you want to call it).

Conventional cars use a transmission (multiple gear ratios), coupled with a differential (fixed gear ratio) that has the effect of reducing engine RPM to the tire RPM. Since power can never be created or lost through gearing, reduction of RPM also has the effect of increasing torque at the tires. HP=RPM*Torque(FTLBS)/5250.

If a conventional car had no gear ratio reduction (or 1:1), a engine at 5000RPM would be rotating the tires at 5000RPM. A typical 26" high tire at 5000RPM would be theoretically moving a car at 386mph.

26"/12"=2.17ft
2.17ft*3.14159=6.80678ft/rev
5000RPM*6.80678ft/rev=34033.9ft/min
34033.9/5280*60=386mph.

So some reduction in tire revolution is required. It has the added benefit of increasing torque at the tire. Using a Corvette as an example (since I am familiar with), has a typical 1st gear final drive ratio of around 10. That means (using the example above), that top speed in 1st gear is 10 times less than above (38.6mph) but torque is multiplied by 10 times as well. So instead of a engine max rated 400ft-lbs of torque, it is actually 4000ft-lbs at the tires. Exactly why many cars can spin tires in 1st gear, but not 2nd. (I have a car that can spin in 4th gear, but that's another story ;P).

Torque divided by the moment arm (radius of tire) gives the force between the tire and pavement. If that force is greater than wind resistance and rolling friction, the car will continue to accelerate until those forces will be equal, at which point the car has hit its top speed.

That's important to note, because the torque is actually an easier mechanism to use to determine acceleration caracteristics.

Problem comes with typical ICEs, since they are non-linear devices. Power peaks at certain RPM, and torque curves are never flat. Because of the non-linear operation, multispeed transmission were developed to help the car perform best in various power bands. 1st gear is for acceleration, 4th gear for cruising, 5th or 6th gear usually overdrive for fuel economy, etc.

Back on topic, electric motors are very linear, and have a very specific torque curve. Because a large amount of low end torque is available, electric cars can chose to eliminate the multispeed transmission. But in doing so, you are left with a one-sized-fits-all scenerio. Either gear the car for lower top speed and higher torque (better acceleration), or for lower torque and higher top speed.

Early Tesla Roadsters suffered from this, as thier single speed models performance was decidedly lackluster. Even so, this Fiskar models seems to be competitive with other 400hp 4000+lb models. Best comparison would be to something like a Dodge Charger SRT-8, with over 400hp and 4200lbs, gets 0-60 in about 5 sec. So this is about a second slower. Not bad for a car that's targeted at a completely different market segment, not a dragstrip racer.
That tells me it' probably geared slightly higher to aid with fuel economy.

Now, if it's "worth" it's $100k price tag, that's a discussion for another day. Does look sexy though.

Sorry for the long post, just that it seems there is a lot of confusion with gear ratios and thier effect on performance.


RE: A 260 hp gas engine?
By fic2 on 2/21/2011 1:51:31 PM , Rating: 2
What car(s) have a typical 26" wheel?


RE: A 260 hp gas engine?
By theapparition on 2/21/2011 3:29:16 PM , Rating: 2
Corvettes have a 26.66" diameter tire (just off my head), along with a myriad of other models. Camaro and mustang are even larger, with the Camaro SS at 28.66" and the Mustang GT at 27.25" diameter.

Plenty of other car models have a much smaller diameter, for example, the Honda Fit has a 23.95" tire, but since the context was about performance, no point in trying to compare a $100 hybrid sports coupe to an entry level econobox.

Still, just modify the numbers a bit.


RE: A 260 hp gas engine?
By mars2k on 2/21/2011 4:11:37 PM , Rating: 2
Great post. What we need is more information not a lot of negativity.

I wonder why they don't use a turbo diesel instead of gas diesels are more efficient particularly at partial loads?

By the way Fisker has been making beautiful exotic automobiles in Switzerland for decades. They are an exclusive and well respected brand overseas. Kudos to them


RE: A 260 hp gas engine?
By BZDTemp on 2/22/2011 9:28:16 AM , Rating: 2
quote:
By the way Fisker has been making beautiful exotic automobiles in Switzerland for decades. They are an exclusive and well respected brand overseas. Kudos to them


I'm confused - what cars are you think of that Fisker Automotive or Henrik Fisker for that matter have made in Switzerland?

The designs from Henrik Fisker that I can think of are some for BMW, Aston Martin, Fisker Coachworks and most recently a sports car by a small German (or is it Dutch) company. Plus of course the car we are seeing in this article and the unused design made for Tesla.


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