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Old 10-24-2011, 01:49 PM   #1 (permalink)
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Default Horsepower, Torque, and Acceleration

So, I sent an email to the Consumer Affairs lady at Fisker asking about the new horsepower ratings now that the 0-60 times have been reduced to 6.3 seconds. Unfortunately, she had no information on the 0-60 in Stealth mode, but she did say that the horsepower and torque numbers remain the same.

I suspect this is true since the car's top speed is still 125mph, but I also suspect this is Fisker playing with the numbers again because we've previously been told that the power has been reduced which resulted in the slower 0-60. The car probably does output 403hp at some point to get it to 125mph, but my guess is that the software limits the horsepower at slower speeds. At 0-60 the horsepower output is probably well less than 400, but they ramp it up at higher speeds.

Dunno... just a guess, but there's no way the HP is the same while the acceleration goes down. Either they were just plain wrong all along, the weight went up, or the HP has been reduced.

-Brian
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Old 10-24-2011, 02:11 PM   #2 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

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Originally Posted by brian
So, I sent an email to the Consumer Affairs lady at Fisker asking about the new horsepower ratings now that the 0-60 times have been reduced to 6.3 seconds. Unfortunately, she had no information on the 0-60 in Stealth mode, but she did say that the horsepower and torque numbers remain the same.

I suspect this is true since the car's top speed is still 125mph, but I also suspect this is Fisker playing with the numbers again because we've previously been told that the power has been reduced which resulted in the slower 0-60. The car probably does output 403hp at some point to get it to 125mph, but my guess is that the software limits the horsepower at slower speeds. At 0-60 the horsepower output is probably well less than 400, but they ramp it up at higher speeds.

Dunno... just a guess, but there's no way the HP is the same while the acceleration goes down. Either they were just plain wrong all along, the weight went up, or the HP has been reduced.

-Brian
I believe that the weight did go up (from a planned number around 5000 to the delivered 5300). That's about a 6% increase, and 5.9 to 6.3 seconds is about a ... 6% increase.[hr]
BTW if you apply the 6% increase to the original Stealth time of 7.9 you get 8.4 seconds.
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Old 10-24-2011, 02:26 PM   #3 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

Well, what I was told recently was that the 0-60 time changed because of the new exhaust, the new inverter, and new software. I don't think it had anything to do with weight.

-Brian
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Old 10-24-2011, 02:35 PM   #4 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

Could be. The software won't change the weight of course, but the exhaust system and inverter might. I wonder what they did with the inverter? Is it liquid cooled?
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Old 10-24-2011, 02:37 PM   #5 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

My understanding is that the batteries aren't powerful enough to drive the electric motors at full power on their own (at the motor's full HP), and that's why the engine has to be running in Sport mode. Now that they've had to reduce the power of the engine, I'm wondering if they're reaching the full HP that the electric motors are capable of, even with power coming from both the batteries and the generator.
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Old 10-24-2011, 02:42 PM   #6 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

I think the software played a part in the HP reduction because it is regulating the RPM's of the ICE. Part of the solution to the noise problem was apparently to tweak how the ICE revs, so apparently they reduced the RPM's to reduce noise, thus reducing power.

-Brian[hr]
*** UPDATE ***

I just got this email directly from Fisker:

I am writing you again to correct something that I sent you earlier. I was told that the torque would not change, but that is incorrect. It will change, from 981 to 959. I am sorry about the confusion.


So, a 22 bhp reduction in torque.

-Brian
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Old 10-24-2011, 02:46 PM   #7 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

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Originally Posted by Mycroft
My understanding is that the batteries aren't powerful enough to drive the electric motors at full power on their own (at the motor's full HP), and that's why the engine has to be running in Sport mode. Now that they've had to reduce the power of the engine, I'm wondering if they're reaching the full HP that the electric motors are capable of, even with power coming from both the batteries and the generator.
At one time, the numbers were (all of these are from memory): 300 kW (ie 400 hp) of electric motor draw maximum; 150 kW draw from batteries; 175 kW draw from generator. All of those may have been approximate in the first place, and/or erroneous, and/or changed as they were all drawn from various tidbits released over time. Still, if they're close, that means there was enough room to drop the generator output by 25 kW and still drive the electric motors at full torque.

Of course, there was also mention somewhere that 125 mph was top continuous speed, not absolute top speed, and that there was a higher but temporary passing speed. So perhaps the 300 kW output is a temporary maximum in the first place, or perhaps there is/was a 325 kW temporary maximum.
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Old 10-24-2011, 06:20 PM   #8 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

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Originally Posted by ct-fiskerbuzz
Of course, there was also mention somewhere that 125 mph was top continuous speed, not absolute top speed, and that there was a higher but temporary passing speed. So perhaps the 300 kW output is a temporary maximum in the first place, or perhaps there is/was a 325 kW temporary maximum.
I recall something like 140 MPH as the absolute top speed that could be sustained for short periods of time.

Maybe Fisker could add a software switch that would let us select the higher power output from the engine even if it makes it more noisy.

-- Fab.
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Old 10-24-2011, 06:23 PM   #9 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

If I remember correctly the car is electronically limited to 125MPH because the batteries overheat at higher speeds.

-Brian
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Old 10-25-2011, 02:12 AM   #10 (permalink)
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Default RE: Horsepower, Torque, and Acceleration

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Quote:
Originally Posted by ct-fiskerbuzz
Of course, there was also mention somewhere that 125 mph was top continuous speed, not absolute top speed, and that there was a higher but temporary passing speed. So perhaps the 300 kW output is a temporary maximum in the first place, or perhaps there is/was a 325 kW temporary maximum.
I recall something like 140 MPH as the absolute top speed that could be sustained for short periods of time.

Maybe Fisker could add a software switch that would let us select the higher power output from the engine even if it makes it more noisy.

-- Fab.
I am all in favor of this option, if it is what is in fact causing the drop in acceleration. I, for one, would much rather have more noise and get to 60 in 5.9 versus 6.3.
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