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Discussion Starter #1
I read a lot about the "instant, head-snapping torque". So I'm wondering if there is something wrong with my car. It doesn't snap my head at all!

When I accelerate from a dead stop (push the go pedal to the metal, including kickdown switch), there is no instant jump in torque, instead it is gradually increased from zero to max, taking a second of two to reach full. I can both feel this and watch it on the power meter. This is on dry road with no sign of the ESP being activated, and no traction issues in the tires.

When I stomp on the pedal while already driving, torque and power meter do jump almost instantly to full.

Can anyone confirm if their car behaves the same way?
 

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Yes, mine behaves the same way and would enjoy more head snapping. I think it's the traction control or ESP causing it to behave that way.
 

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Tip: Dont use kickdown at a dead stop. Just step on it all the way no kickdown and when you get to about 5-8 mph then use kickdown, its a little quicker. Also if you have regen paddles putting the car in D- makes it a little quicker whenever you step on it opposed to having it in D+.
 

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Tip: Dont use kickdown at a dead stop. Just step on it all the way no kickdown and when you get to about 5-8 mph then use kickdown, its a little quicker. Also if you have regen paddles putting the car in D- makes it a little quicker whenever you step on it opposed to having it in D+.
I'd say that tip is spot on. :)

Even though that torque is "instant", the motor does need a second or two to get to max torque. Whereas an ICE motor would need to reach a certain RPM (which can take much longer).

So if you're doing it from a dead stop, not only does the motor have to get the car rolling, but it needs that second to reach max torque.

Which, all things considered, it's still very "neck snapping" (exaggeration) even at a dead stop. My ICE is gradual compared to the brute force of the ED.
 

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There is also going to be less power if the battery is low in power, and there is also a maximum available power indicator in the format of a 3 bar display with kW next to it. The more bars, the more power available. When the indicator is full, if you hammer the kickdown button under the accelerator pedal then you should get the 'neck snapping' acceleration.
 

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It's the ESP causing that - even the turbos and turbo diesels had the fueling map delayed in 1st and 2nd gears to prevent wheelspin.
 

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It's the ESP causing that - even the turbos and turbo diesels had the fueling map delayed in 1st and 2nd gears to prevent wheelspin.
Interesting. If ESP is doing that, shouldn't the light illuminate when it activates?

During my time testing Madison's ED (and having much fun with that kickdown pedal) I experienced that very slight "lag" as well, but no ESP light. :shrug:
 

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It's the ESP causing that - even the turbos and turbo diesels had the fueling map delayed in 1st and 2nd gears to prevent wheelspin.
The gas cars are much slower off the line than the EV's. ESP will limit wheelspin on both the gas and EV's, however even with the ESP getting itself involved the EV's are capable of strong torquey acceleration when there is available boost power.
 

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Discussion Starter #9
Thanks for all the comments and suggestions. I'll try what Finest said.

IMHO, it's not the ESP: The torque-ramp-up-time is the same, no matter what road condition, (dry or moist), only on really wet and slippery roads will EPS kick in noticeably, then it's much slower.

And it's not max power limit. I haven't seen less than 3 bars in a long time!

Neo: There is no reason for the motor to "need time to get to max torque" any permanent-magnet AC motor can produce max torque at standstill, instantly, if driven that way.

My best guess is that MB decided to limit torque at very low speed to make it easier on the ESP and built this into the inverter. With truly instant torque from standstill, we'd have ESP kick in every time. Most industrial AC motor drives have some sort of torque ramp-rate limit built in for the same reason - don't want to smoke your conveyor belt every time you turn it on. Of course, those don't have ESP.
 

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Thanks for all the comments and suggestions. I'll try what Finest said.

IMHO, it's not the ESP: The torque-ramp-up-time is the same, no matter what road condition, (dry or moist), only on really wet and slippery roads will EPS kick in noticeably, then it's much slower.

And it's not max power limit. I haven't seen less than 3 bars in a long time!

Neo: There is no reason for the motor to "need time to get to max torque" any permanent-magnet AC motor can produce max torque at standstill, instantly, if driven that way.

My best guess is that MB decided to limit torque at very low speed to make it easier on the ESP and built this into the inverter. With truly instant torque from standstill, we'd have ESP kick in every time. Most industrial AC motor drives have some sort of torque ramp-rate limit built in for the same reason - don't want to smoke your conveyor belt every time you turn it on. Of course, those don't have ESP.
Can't disagree with that theory, sounds more believable than mine! :D
 

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I would expect that the motor controller is limiting initial torque, to keep wheel spin to a minimum. As rpm increases torque drops off accordingly, torque = (5252 x horsepower)/rpm. If there is more torque available at 5mph then right at take off, that is a function of the controller and not the motor. Using TC to control wheel spin due to high intial torque does not make much sense.
 

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Right, if it was ESP the light would flash. Motor controller is the cause, just like the fuelling map in the diesels and gassers.
 

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Personally I've found the initial take off quite brisk, although I would like a bit more thank you very much. Enough is never enough.

I have used the technique to roll into the throttle at 75% power for 1/2 second and then jam it to kickdown to get that little extra head snap feeling, but generally I just wait for green and mash it. My lifetime average KWh/100km is 20, and I rarely get above 30% ECO. Fun. It's why I bought this car!


My best guess is that MB decided to limit torque at very low speed to make it easier on the ESP and built this into the inverter. With truly instant torque from standstill, we'd have ESP kick in every time.
+1 That's what I believe too.

The Chevy Spark EV chirps it's tires from a dead stop, which I consider to be an example on lack of motor controller tuning, although the effect is useful to shock onlookers. ;-)

The torque of the electric motor is easily enough to break traction on the rear tires. I've managed to confuse the traction control/motor controller by shifting the balance of the car under hard turn in and chirp the rears until the ESP symbol flashes notifying me the traction control is working.

Smart may certainly have spent time tuning the motor controller to avoid messy and inefficient traction control to the detriment of some additional noises and more aggressive take off.
 

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Discussion Starter #14
I paid a little more attention yesterday and tried what Finest said, but couldn't reproduce it. Acceleration from dead stop is the same no matter if D + or -, if kickdown pushed or not. Even on a rolling start, it will pick up where it would be at that speed. The minimum speed for instant full power is between 20 and 25 mph.

More likely it's really motor rpm, but in the ED that's the same thing. It may be as simple as a motor current limit in the drive - In standstill, the motor would take near infinite current, if provided. As the motor speeds up and builds back-emf, it takes more power at the same current, until power is the limiting factor and current starts to drop.

Motor current is another word for torque in a permanent magnet motor.
 

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..my take...after driving the ED over in Amana I found out that the kick down feature was NOT the head snapping acceleration that everybody says these cars have....while moving and hitting the switch there was some increase in acceleration but nothing to right home about it....the firs time was in an incline from about 10mph...I was expecting a "head to the rest" snap and I was very disappointed that it never came...several more try resulted in the same let down feeling...I'll have to say that the comfort ride is quite amazing...

Jetfuel...now...a hair dryer is another story....
 

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I guess my car has too many miles to be a valid comparison then. :D :shrug:

Your hair dryer? Makes the ED seem like it's sitting still!!!!
 
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