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      10-17-2019, 10:00 AM   #81
//TMT
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Drives: 2020 X2 M35i, 2005 Volvo V50T5
Join Date: Sep 2019
Location: Eastern Massachusetts

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Quote:
Originally Posted by rice_rocket88 View Post
I would have to say it ultimately is a disengaging feel, so it would be a lurch forward as if you popped the car into neutral. It would make sense of the regenerative braking but in my mind I *KNOW* it's literally the transmission disengaging, because it's the same "jerk" when you take the foot off the brake and it clunks back in gear/engages. This is NOT present at all in the sports mode. It actually is not at all present in my wife's 2016 X1.
So, the brakes are purely friction devices and can't put any energy back, like a hybrid car might. The braking comes from engine braking, which the car implements by keeping the transmission in gear and locking the torque converter. It cuts off the injectors, so there is purely kinetic energy driving the engine and alternator. I believe that this regen behavior is disabled in Sport. And as you observe, the 2016 X1 didn't have this regen feature.

Quote:
The dead spot is a completely different issue that is also exaggerated by the transmission clunking back into gear AND the dead throttle input.
It's the torque converter unlocking that causes this jerk, if my theory is correct anyway. And yes as I said the dead spot is a different issue. I'm not trying to fork the thread, just trying to explore the issues being discussed.

Quote:
I would think that it does not matter if the battery is fully charged or not, because the regenerative braking is a function of braking to gain energy. Even if the car is fully charged and then started I would think the charging system will still act the same in that aspect.
Yes, but if the battery is fully charged, the system may not be calling for this behavior. The only reason I mentioned it is as a way to test. If it *doesn't* happen with a charged battery, I believe that would confirm. If it *does* happen, it's still inconclusive.
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