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Understanding the gas pedal in my car (2020 AMG C43)
Can someone explain to me, or point me to a source, that clarifies what the kick down part of the gas pedal actually does? Here are a couple questions from different scenarios:
1. If I have my car in Comfort mode and I pressed my gas pedal all the way down but not far enough to initiate the kick down part, is the car sending 100% of its power? What percentage in power output is the car currently at with the gas pedal at this point?
2. If I'm still in Comfort mode and I pressed my gas pedal to the floor, all the way down past the kick down and I can no longer press the gas pedal any further, what does this actually do?
3. Do the results from the above scenarios change if I was in Sport+? I know that the throttle mapping changes in Sport+ but not sure what max power is at the point of when the kick down begins and then again at the point of flooring the pedal all the way.
There is no difference in power output from the engine with or without kickdown. The kickdown instantly downshifts to the lowest gear for maximum acceleration and holds the gear all the way to redline. Paddle shifting is not possible during kickdown. It will basically shift gears to achieve maximum acceleration. When the transmission is in manual mode, it doesn't react to the kickdown. It's only if you are in automatic mode. A similar thing can be accomplished in manual mode, by pressing and holding the downshift paddle for a second or two to drop down to the lowest possible gear at once.
This is good Intel. I also have a 2020 and noticed a "click" when putting my foot all the way down to the floor. Is this click the "kick down" your describing? What is the intended purpose of the kickdown?
This is good Intel. I also have a 2020 and noticed a "click" when putting my foot all the way down to the floor. Is this click the "kick down" your describing? What is the intended purpose of the kickdown?
I think your screen grab just answered my question. Sounds like a waterd down launch control
This is good Intel. I also have a 2020 and noticed a "click" when putting my foot all the way down to the floor. Is this click the "kick down" your describing? What is the intended purpose of the kickdown?
Yes, it is. Kickdown as explained above and what OP was essentially asking about. Kickdown has been a staple feature of automatic transmissions since I can remember. Personally, I think it has somewhat lost its relevance in modern computer controlled automatic transmissions, because they downshift anyway based on driver input. Even if you don't push the throttle all the way past the kickdown point, the transmission will still downshift pretty much to the lowest gear possible in response to the throttle input. The downshift maybe a bit more delayed, whereas the kickdown switch tells it to immediately downshift to the lowest possible gear, but I'm not entirely sure if there's a perceptible difference. Perhaps the biggest difference is that with kickdown it will not short shift and basically run all the way to redline, and you can also not short shift using the paddles, whereas it's possible that the transmission upshifts earlier than redline while accelerating w/o activating kickdown.
I wish kickdown was active in manual mode as it was in my previous Audi RS5, because pressing and holding the downshift paddle is somewhat slow as it takes about a second for it to finally downshift to the lowest possible gear. In my RS5, I could stomp on the throttle in manual mode and it would instantly downshift to the lowest possible gear. Or I would love to have what Koenigsegg did in the Jesko with their MCT transmission. In the Jesko, the paddles have two stages. The first stage does a normal sequential shift, but if you pull the paddles all the way it will either instantly downshift to the lowest possible gear, or the highest possible gear based on the current rpm. I think that' the ultimate solution.
Last edited by superswiss; Jul 23, 2020 at 06:50 PM.
I think your screen grab just answered my question. Sounds like a waterd down launch control
Not really. Launch control is for launching from a stop, whereas kickdown is for maximum acceleration once you are already in motion, but as I said above, its relevance today is kinda questionable because the transmissions are programmed to downshift anyway based on the amount of throttle input etc. I'm not sure you actually get more acceleration triggering kickdown vs just pushing the throttle all the way, but not past the resistance point. Would have to really try it a few times in the real world. To be honest, I haven't used kickdown in a long time, other than my previous RS5 in manual mode, because that was the quickest way to downshift to the lowest possible gear for maximum acceleration. In my C63 if I need maximum acceleration I press and hold the downshift paddle as I'm giving it full throttle and it just about downshifts all the way by the time I'm mostly in the passing lane and ready to fly by the car(s) I'm trying to pass. So it kinda works as implemented.
I think the main function of the kickdown is if the transmission may not readily downshift all the way by simply giving it full throttle. By adding a kickdown switch at the end of the throttle pedal, the driver can signal the transmission to downshift all the way instantly. So really it might just remove a fraction of a second for downshifting all the way. It's also somewhat tied to the drive mode. In S+, the transmission is more willing to kick down early in reaction to normal throttle input, but in C it's a bit more reluctant, so in C one can use the kickdown to notch it into kicking down the gears earlier.
Last edited by superswiss; Jul 23, 2020 at 07:15 PM.
BTW, ultimately this is about getting the engine into the power band and start making full power as soon as possible for maximum acceleration. While there is no difference in power output based on drive mode etc., an engine only makes full power close to redline. Power is a function of torque and rpm, specifically the formula is Power = Torque * RPM / 5252. Power is the rate of work and it determines how fast the car accelerates and also the top speed. The faster a car drives, the more power is needed to overcome wind resistance and maintain or reach a certain speed. The higher the power, the more work is performed in a given time, which means the car is acceleration faster. So maximum acceleration occurs at peak power (not peak torque as is popular believe), so the quicker the transmission can get the RPMs near peak power, the faster the car accelerates.
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