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 Post subject: how to disable the speed limiter
PostPosted: Sun Oct 25, 2015 10:31 pm 
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Joined: Sun Oct 25, 2015 9:59 pm
Posts: 3
I'd like to take my lovely Spark EV for a spin around Sonoma Raceway, but that 90 MPH speed limiter is a royal pain in the butt!
Can it be removed / disabled / reset / overridden / defeated / obliterated ? (For off-road use only, of course).
Are there tuners in California who are familiar with these cars? Being rather a petrol head I know plenty of tuners who work on gas engines & management, but not on EV cars...


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 Post subject: Re: how to disable the speed limiter
PostPosted: Mon Oct 26, 2015 1:43 pm 
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Joined: Sat Sep 12, 2015 1:48 pm
Posts: 80
I cannot answer your question but I'd like to add to it since you brought up the speed limiter.
To start with, what happens if you hit 90 and keep the pedal to the metal? Does it act like cruise control and you stay at 90, up and down hills and all? If so I would like a "dial in" limiter control to take the place of the cruise control. With this, you could keep your foot on accel, not have to worry about the speed limit, (dial "5 over" when limit changes up or down) and letting your foot up will allow slowing as needed (ie: allowing a car to merge on the highway) without having to cancel the cruise control, then resume.
I've had several occasions where I came up on traffic too quickly by being "held" in cruise control mode. I don't use it often enough to instantly remember to tap the brake to coast down vs letting up on accelerator to coast down. The ability to dial in the max speed would give more control in my opinion.

David


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 Post subject: Re: how to disable the speed limiter
PostPosted: Mon Oct 26, 2015 6:41 pm 
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Joined: Wed May 29, 2013 12:00 am
Posts: 536
Location: Portland, OR
pierred wrote:
I'd like to take my lovely Spark EV for a spin around Sonoma Raceway, but that 90 MPH speed limiter is a royal pain in the butt!
Can it be removed / disabled / reset / overridden / defeated / obliterated ? (For off-road use only, of course).
Are there tuners in California who are familiar with these cars? Being rather a petrol head I know plenty of tuners who work on gas engines & management, but not on EV cars...


I haven't found anybody able and willing yet. If you figure out how, I'll gladly put my money where my mouth is. I'd shave seconds off my time at PIR if I could ditch the speed limiter...there are two long stretches where I only accelerate about half of the distance, the rest I have time to see the sights.

Bryce


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 Post subject: Re: how to disable the speed limiter
PostPosted: Mon Oct 26, 2015 7:02 pm 
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Joined: Sat Jun 13, 2015 1:54 pm
Posts: 243
Location: SoCal
Gosh, that motor must be spinning mighty fast at 90 mph. Just because we can't hear the mechanical stresses doesn't mean they aren't there!

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2015 Spark EV: 2LT, DCFC, Summit White


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 Post subject: Re: how to disable the speed limiter
PostPosted: Mon Oct 26, 2015 7:51 pm 
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Joined: Sat Jul 27, 2013 9:52 am
Posts: 125
Location: Los Gatos
Nashco wrote:
pierred wrote:
I'd like to take my lovely Spark EV for a spin around Sonoma Raceway, but that 90 MPH speed limiter is a royal pain in the butt!
Can it be removed / disabled / reset / overridden / defeated / obliterated ? (For off-road use only, of course).
Are there tuners in California who are familiar with these cars? Being rather a petrol head I know plenty of tuners who work on gas engines & management, but not on EV cars...


I haven't found anybody able and willing yet. If you figure out how, I'll gladly put my money where my mouth is. I'd shave seconds off my time at PIR if I could ditch the speed limiter...there are two long stretches where I only accelerate about half of the distance, the rest I have time to see the sights.

Bryce


The speed limiter won't exist a separate item - it will almost certainly be integrated into the motor control software.

Even if you did patch the software to remove the limit, I don't think you would gain much. As you can see from the graph the torque is dropping off very rapidly at 90mph and this is dictated mainly by the motor design and battery voltage.

kevin
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 Post subject: Re: how to disable the speed limiter
PostPosted: Mon Oct 26, 2015 8:19 pm 
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Joined: Sun Oct 25, 2015 9:59 pm
Posts: 3
Nashco wrote:
I haven't found anybody able and willing yet. If you figure out how, I'll gladly put my money where my mouth is. I'd shave seconds off my time at PIR if I could ditch the speed limiter...there are two long stretches where I only accelerate about half of the distance, the rest I have time to see the sights.

Bryce

I hear you. With the race cars, we typically figure the gear ratios by the longest straight, try to hit the rev limiter a bit before the brake point, then stagger all the other gears down from there. But here, uh, not even sure where to look. I would imagine it's just in the software or firmware and easy to modify. Has anyone reverse-engineered the code?


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 Post subject: Re: how to disable the speed limiter
PostPosted: Mon Oct 26, 2015 8:31 pm 
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Joined: Sun Oct 25, 2015 9:59 pm
Posts: 3
kevin wrote:
The speed limiter won't exist a separate item - it will almost certainly be integrated into the motor control software.

Agreed, that is most likely.
kevin wrote:
Even if you did patch the software to remove the limit, I don't think you would gain much. As you can see from the graph the torque is dropping off very rapidly at 90mph and this is dictated mainly by the motor design and battery voltage.

kevin

I've seen that plot before and it doesn't reflect the acceleration I experienced (perhaps it's for a different model?). Given that acceleration is proportional to axle torque, it should almost completely vanish according to the blue curve. Granted, I didn't have a proper data logger with me last time I tried, but the car was definitely still pulling like a freight train when all of a sudden it hit the speed limiter and something like "90MPH speed limit" showed up in red in the center console. The speed limiter felt like a soft rev limiter ("dah-dah-dah-dah-dah") but induced a stronger stutter in the car than a rev limiter would on a regular car. That was very surprising, in fact. My estimation is that we are leaving a good 20mph on the table, perhaps more.


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 Post subject: Re: how to disable the speed limiter
PostPosted: Tue Oct 27, 2015 6:40 am 
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Joined: Fri May 01, 2015 5:52 am
Posts: 928
Location: KC,MO
Another obvious thing to consider is, Electric Motors have Red Lines, just like Gas Engines have Red Lines.
Things start to break when you go beyond the stated red line.
If not immediately, then accelerated aging is happening and someday things will break.

Only the design engineers know for sure what the motor red line is.

I agree though, it does pull hard to 90 then just smoothly sits there. It 'Feels' like there is more, but who knows?

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Used '14 2LT w/ DCFC.
In the middle of the country.
Far from any of its sibs.


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 Post subject: Re: how to disable the speed limiter
PostPosted: Wed Oct 28, 2015 10:14 am 
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Joined: Wed May 29, 2013 12:00 am
Posts: 536
Location: Portland, OR
There is still plenty of motor speed and power left on the table if you have a 2014, which has the lower gear ratio. The 2015+ went to a higher gear ratio, but the top speed limiter remains at the same 90 mph. Keep in mind that our motor spins very slowly compared to typical EVs, so I expect we'd get to power limitation (aero drag overcomes available motor power) before motor speed limits if we didn't have the speed limiter in place.

Bryce


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 Post subject: Re: how to disable the speed limiter
PostPosted: Wed Oct 28, 2015 10:32 am 
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Joined: Sat Jun 13, 2015 1:54 pm
Posts: 243
Location: SoCal
Nashco wrote:
There is still plenty of motor speed and power left on the table if you have a 2014, which has the lower gear ratio. The 2015+ went to a higher gear ratio, but the top speed limiter remains at the same 90 mph. Keep in mind that our motor spins very slowly compared to typical EVs, so I expect we'd get to power limitation (aero drag overcomes available motor power) before motor speed limits if we didn't have the speed limiter in place.

Bryce

Car and Driver tested the ICE 2014 Spark to a drag limited 103 mph. GM obviously has some rationale to limit the top end of the EV variant. If that rationale was not "motor speed limits", what components of the drive train, or vehicle dynamics, do you think caused them to limit the EV to 90mph?

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2015 Spark EV: 2LT, DCFC, Summit White


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