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Discussion Starter · #1 ·
......for about a hundred feet before he jettisoned by me.....
 

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Because the Lambo's driver was reading his email? Love the Fisker looks, but it does not compare with the Lamborghini in terms of acceleration. Here are the Lambo specs:
0-30 1.6s
0-40 2.2s
0-50 2.6s
0-60 3.2s
Fisker 0-60 is in the 6s range - could not find any official number other than the Fisker statement of 6.5 s
 

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Unbeknownst to him, I had the warp drive option installed on my Karma.....or did he just have poor reaction time as he wanted to dice from the get go.....I did have him for a bit until his Bird of Prey Klingon Warship obliterated my BatMobile.
 

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I think the Karma is faster in the first 100 feet if you don't drop the clutch in the Lambo. The Karma is just more instant. In the Lambo, you have to do many things just right to make for the ultimate launch, but in the Karma, you just mash the accelerator. That's the beauty of the Karma. From stop lights you whiz away from everybody easily even in stealth mode. 0-30mpg is very quick because of the instant torque.
 

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Sigurd said:
I think the Karma is faster in the first 100 feet if you don't drop the clutch in the Lambo. The Karma is just more instant. In the Lambo, you have to do many things just right to make for the ultimate launch, but in the Karma, you just mash the accelerator. That's the beauty of the Karma. From stop lights you whiz away from everybody easily even in stealth mode. 0-30mpg is very quick because of the instant torque.
Exactly my thoughts upon reading the original post-- I'm not surprised that a powerful EV can beat a gas guzzler in the initial launch phase. Maybe we should promote a new metric of auto bragging rights: "Oh yeah? What's your zero-to-five-mph time???" :D
 

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Since Sigurd has both he probably is the most qualified to make a comparison. Agree that instant torque availability is nice. Hope though that next iteration of the karma pushes the performance a little more - there were rumors about a gearbox, anyone having some info on that?
 

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Ok, I have a key question I am asking myself for long time. What does horsepower or especially torque say about a car. We know the Karma has 959 lb/ft torque which is the same as a Bugatti Veryon. Is it as fast as the Bugatti. We know it's not. Can anybody explain torque and horsepower?
THANK YOU...another sunny day in Socal!
 

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Technically, horsepower is a unit of power (energy divided by time), just like watts. In fact, one horsepower is about 735 watts. A 100 watt light bulb is thus about .14 horsepower.

Torque is a unit of force, specifically of twisting force. The effect of that force depends on how it is applied. See wikipedia for a nice illustration. "Newton meter" is a better unit for torque (because English units get kind of messed-up). The Karma has about 1300 Nm of torque.

I'll just quote the next bit straight from wikipedia:
Understanding the relationship between torque, power and engine speed is vital in automotive engineering, concerned as it is with transmitting power from the engine through the drive train to the wheels. Power is a function of torque and engine speed. The gearing of the drive train must be chosen appropriately to make the most of the motor's torque characteristics. Power at the drive wheels is equal to engine power less mechanical losses regardless of any gearing between the engine and drive wheels.
In a mechanical motor, power equals torque multiplied by RPM. If your torque were to remain the same at (say) 3000 and 6000 RPM, you would get twice as much power (double the horsepower) at 6000 RPM than at 3000. (But it doesn't, so, you don't. :D) Still, with conventional (internal combustion) engines, maximum torque and power occur at some nonzero RPM value.

With electric motors, maximum torque normally occurs at zero RPM (and in an ideal electric motor—which doesn't actually exist—torque is inversely proportional to RPM, i.e., it goes to infinity at zero RPM). Meanwhile power (measured in horsepower or watts) is essentially constant—which is why torque drops off with 1/RPM: just as in the mechanical motor, (delivered) power equals torque times RPM, so as the thing spins faster, for its power to remain the same, its torque has to diminish.

In real electric motors, torque still starts at maximum (but not actually infinity) at zero RPM, stays pretty much flat up to some smallish RPM value, then begins to drop off in the 1/RPM style. Meanwhile, delivered power starts at 0 (none is delivered at 0 RPM due to zero times anything equals zero), but otherwise stays fairly flat through the entire RPM range. Consumed power stays completely constant. (The difference between the two shows up as heat: at zero RPM the motor heats up pretty quickly, which is why you can burn out some electric motors by putting them in a vise. You can use current limiter devices though, which every electric car has both so that you can control acceleration and to prevent overheating.)

To run a car on a straight and level road, you simply need to supply enough power (horsepower) to overcome air and tire-rolling resistance. The more power you supply, the faster the car will (eventually) go. To get a car to go from "not moving at all" to "moving rapidly" in as few seconds as possible, though, you must supply a huge amount of torque—twisting force—to the tires. Twisting the tires is what propels the car forward. The delivered power is, as always, "torque (at the wheels) times RPM (at the wheels)". The Bugatti is, via gearing and clutches, able to supply a lot of torque over a very broad tire-RPM-range, giving it a wide range of speeds at which it can deliver a lot of horsepower. (But note: every time you move to a higher gear, you drop the maximum deliverable torque.)

The Karma, meanwhile, can deliver lots of torque at low speeds (thanks to its electric motor) but less torque at higher speeds (due to its lack of gearing), and it has a lot fewer horsepower (~400 vs ~1000) and weighs/masses more (the Veyron weighs under 4200 lbs, vs 5300ish for the Karma), so the Veyron continues to supply both high torque and high horsepower even at 100+ mph, to a lighter car, while the Karma's torque has dropped way off by then.
 

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ct-fiskerbuzz said:
The Karma, meanwhile, can deliver lots of torque at low speeds (thanks to its electric motor) but less torque at higher speeds (due to its lack of gearing), and it has a lot fewer horsepower (~400 vs ~1000) and weighs/masses more (the Veyron weighs under 4200 lbs, vs 5300ish for the Karma), so the Veyron continues to supply both high torque and high horsepower even at 100+ mph, to a lighter car, while the Karma's torque has dropped way off by then.
Has Fisker ever released any torque curves? Part of the issue is that Fisker is using permanent magnet synchronous motor which maxes out at 6000 RPM. So it has to use a 4:1 gear ratio to get a reasonable top speed.

Here are some Tesla curves I managed to dig up. They use AC induction motors that max out around 14000 RPM.



An old Model S curve. Things might have changed a bit.
 

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ct-fiskerbuzz said:
Technically, horsepower is a unit of power (energy divided by time), just like watts. In fact, one horsepower is about 735 watts. A 100 watt light bulb is thus about .14 horsepower.

Torque is a unit of force, specifically of twisting force. The effect of that force depends on how it is applied. See wikipedia for a nice illustration. "Newton meter" is a better unit for torque (because English units get kind of messed-up). The Karma has about 1300 Nm of torque.

I'll just quote the next bit straight from wikipedia:
Understanding the relationship between torque, power and engine speed is vital in automotive engineering, concerned as it is with transmitting power from the engine through the drive train to the wheels. Power is a function of torque and engine speed. The gearing of the drive train must be chosen appropriately to make the most of the motor's torque characteristics. Power at the drive wheels is equal to engine power less mechanical losses regardless of any gearing between the engine and drive wheels.
In a mechanical motor, power equals torque multiplied by RPM. If your torque were to remain the same at (say) 3000 and 6000 RPM, you would get twice as much power (double the horsepower) at 6000 RPM than at 3000. (But it doesn't, so, you don't. :D) Still, with conventional (internal combustion) engines, maximum torque and power occur at some nonzero RPM value.

With electric motors, maximum torque normally occurs at zero RPM (and in an ideal electric motor—which doesn't actually exist—torque is inversely proportional to RPM, i.e., it goes to infinity at zero RPM). Meanwhile power (measured in horsepower or watts) is essentially constant—which is why torque drops off with 1/RPM: just as in the mechanical motor, (delivered) power equals torque times RPM, so as the thing spins faster, for its power to remain the same, its torque has to diminish.

In real electric motors, torque still starts at maximum (but not actually infinity) at zero RPM, stays pretty much flat up to some smallish RPM value, then begins to drop off in the 1/RPM style. Meanwhile, delivered power starts at 0 (none is delivered at 0 RPM due to zero times anything equals zero), but otherwise stays fairly flat through the entire RPM range. Consumed power stays completely constant. (The difference between the two shows up as heat: at zero RPM the motor heats up pretty quickly, which is why you can burn out some electric motors by putting them in a vise. You can use current limiter devices though, which every electric car has both so that you can control acceleration and to prevent overheating.)

To run a car on a straight and level road, you simply need to supply enough power (horsepower) to overcome air and tire-rolling resistance. The more power you supply, the faster the car will (eventually) go. To get a car to go from "not moving at all" to "moving rapidly" in as few seconds as possible, though, you must supply a huge amount of torque—twisting force—to the tires. Twisting the tires is what propels the car forward. The delivered power is, as always, "torque (at the wheels) times RPM (at the wheels)". The Bugatti is, via gearing and clutches, able to supply a lot of torque over a very broad tire-RPM-range, giving it a wide range of speeds at which it can deliver a lot of horsepower. (But note: every time you move to a higher gear, you drop the maximum deliverable torque.)

The Karma, meanwhile, can deliver lots of torque at low speeds (thanks to its electric motor) but less torque at higher speeds (due to its lack of gearing), and it has a lot fewer horsepower (~400 vs ~1000) and weighs/masses more (the Veyron weighs under 4200 lbs, vs 5300ish for the Karma), so the Veyron continues to supply both high torque and high horsepower even at 100+ mph, to a lighter car, while the Karma's torque has dropped way off by then.
Good explanation. thank you!
 

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doug said:
Has Fisker ever released any torque curves?
If so, I have not seen them.

Here are some Tesla curves I managed to dig up. They use AC induction motors that max out around 14000 RPM.

The torque and power curves in this graph (red and blue lines respectively) illustrate what's so great about electric motors: torque hits its maximum almost immediately, running linearly to the right, and power (which is torque times RPM, as usual) ramps up smoothly until you hit the Magic Cutoff Point (the first knee in the curves, around 5000 RPM). At that point, power runs almost linearly out to the right until you hit the second knee (around 65000 RPM), and then drops off a bit.

The first knee represents the transition into (or out of, as it were) "real electric motor" (which has a maximum torque) onto "ideal electric motor" (where torque is the inverse of RPM). The second represents the transition back out of "ideal" into "real", where you start seeing friction and winding losses (EMF) and so on.

The curves will be different for permanent magnet switched-reluctance motors, but I don't know precisely what they will look like.
 
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