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Discussion Starter · #1 ·
I'm no automotive engineer, nor do I play one on TV, but there is something I just don't understand about the Karma's acceleration.

With more torque than the LaFerrari and the Bugatti Veyron why isn't the Karma a <4s car to 60 mph? At a minimum, it should thrash the Model S on acceleration stats.

I know that weight has a ton (pun intended) to do with it but come on, the Karma only weighs 2 linebackers more than a Model S and its 0-60 time is ~4s.

Is it all about the gear ratio of that single speed transmission then?

OR, did Fisker just purposely water down what the car can deliver to extend the life of the drivetrain?
 

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Without going into too much detail, it's all about extending the life of the battery...at least from what I understood.
 

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I'm no automotive engineer, nor do I play one on TV, but there is something I just don't understand about the Karma's acceleration.

With more torque than the LaFerrari and the Bugatti Veyron why isn't the Karma a <4s car to 60 mph? At a minimum, it should thrash the Model S on acceleration stats.

I know that weight has a ton (pun intended) to do with it but come on, the Karma only weighs 2 linebackers more than a Model S and its 0-60 time is ~4s.

Is it all about the gear ratio of that single speed transmission then?

OR, did Fisker just purposely water down what the car can deliver to extend the life of the drivetrain?
As I understand it, it's primarily due to the fixed gear ratio. With the single gearing driving the Karma is like always being in 4th gear. It's a compromise between initial acceleration and top-end speed. Even Henrik has suggested that a multi-speed gearbox would dramatically improve off-the-line performance. Apparently this is hard to do; Tesla had big problems with their first-gen roaster gearbox and gave up, going back to a single gearing.

There's always the brute force method: Throwing more power and torque at the current gearing will also improve performance, but as been discussed, the amount of power extracted from the battery is managed to balance output with battery life, range and thermal management. I've heard a few people suggest a short-burst "launch mode" which would allow for greater output for a few seconds to improve 0-60 times.

Brent
 

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I've heard a few people suggest a short-burst "launch mode" which would allow for greater output for a few seconds to improve 0-60 times.
I have been a staunch advocate of Launch/Short Boost mode that would relax the limits on the inverters and allow the car to briefly use full power for short periods of time for off-the-line starts or for passing, with the full understanding that you have to pay the price in range. I think this feature would make the Karma even more competitive with the Model-S performance version and even with the ICE-powered cars in the Karma's price range. So far, no response from Fisker ....
 

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Discussion Starter · #5 ·
So gearing aside...is it reasonable to assume that as battery technology improves, we could potentially swap in a new battery pack and dramatically change performance of the vehicle?
 

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So gearing aside...is it reasonable to assume that as battery technology improves, we could potentially swap in a new battery pack and dramatically change performance of the vehicle?
Without changing the software that controls the inverters and the motors, putting in a bigger battery just gets you more range, which is not a bad thing by itself, but to get higher performance, the software needs to be changed to allow the full power to flow to the motors.
 

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I predict the following: Just as Hot-Rodders were unsatisfied with factory performance, and found ways to hop up their engines, and, with the advent of electronics there are chips to enhance engine performance, there will be after market add-ons to allow the Karma to utilize untapped power.
 

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I have been a staunch advocate of Launch/Short Boost mode that would relax the limits on the inverters and allow the car to briefly use full power for short periods of time for off-the-line starts or for passing, with the full understanding that you have to pay the price in range. I think this feature would make the Karma even more competitive with the Model-S performance version and even with the ICE-powered cars in the Karma's price range. So far, no response from Fisker ....
+1. If they get it done, I will be getting a Fisker too.
 

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From my truncated research it seems as if Fisker Automotive had a compressed validation schedule; so they erred on the side of caution and detuned the powertrain significantly. I have spoken to a few powertrain engineers and one of them claimed that the powertrain is currently running significantly below the "safe" threshold. Apparently Fisker Automotive wanted to iron out all the powertrain bugs prior to unleashing the full potential of the vehicle. I may be wrong here but I think many Fisker owners would sign up immediately for a performance software upgrade and the ability to have the vehicle increase SOC while driving in sport.
 

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I would sign up. I wonder if there are some ex-FA engineers that want to have a nice side engineering and consulting business. Sort of like RUF for Porsche.
 

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From my truncated research it seems as if Fisker Automotive had a compressed validation schedule; so they erred on the side of caution and detuned the powertrain significantly. I have spoken to a few powertrain engineers and one of them claimed that the powertrain is currently running significantly below the "safe" threshold. Apparently Fisker Automotive wanted to iron out all the powertrain bugs prior to unleashing the full potential of the vehicle. I may be wrong here but I think many Fisker owners would sign up immediately for a performance software upgrade and the ability to have the vehicle increase SOC while driving in sport.
I would definitely be interested in that upgrade, as long as it is properly validated and shown to be in the Safe zone. As much as I would like to have the additional "Turbo Boost" or "Launch" mode, I would not want to have to replace an inverter or traction motor.
 

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I would be in if they find a way to tap more power to give my Karma a boost.
 

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Needless to say most of us would take this up if the group/company could show no negative consequences/permanent damage/reliability issues that would result from unleashing more performance. It would also have to be worth it - i.e. going 0-60 in 5.0s or less... (not just shaving off a half second or so).
 
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