Gas Pedal Travel

geermx · 12-09-2007

I've noticed that when pressing the gas pedal it travels to a stopping point and then with added pressure goes beyond the initial stopping point. It almost feels like a pressure sensitive switch. Has anyone else noticed this and if so what is the purpose?

**DansSlk** · 12-09-2007

That would be the resistance spring for Kickdown

geermx · 12-09-2007

I apologize for not knowing what that is or what it's purpose is, could you elaborate?

**DansSlk** · 12-09-2007

Sure no worries.

If your car is a manual then this does not apply.

Kickdown is activated when the pedal value reads over 100%, the ECU (engine control) reads that value and sends a message to the TCU (transmission control) saying that you want full acceleration.

This causes the transmission to shift into the lowest possible gear for the current engine speed, as soon as it confirms that has taken place the ECU opens the throttle fully and the car will run to its redline then shift right up to the maximum engine speed in the highest gear then when you ease off of the pedal the car returns to the state it was in before kickdown was activated (or as close as possible).

As i say this has no effect on a manual but the spring is left installed so Merc only have to produce one throttle pedal for the car.

mtiede · 12-09-2007

One additional point. This is not a feature unique to MB, but, as far as I know, all automatic transmissions have this feature.

Move to the passing lane and floor it

**DansSlk** · 12-09-2007

Yep thats true, and most electrically operated manuals have it also

geermx · 12-09-2007

Interesting... I guess I never noticed it before, but then again I don't remember flooring my Explorer.

**DansSlk** · 12-09-2007

Not all vehicles have the detent so in some kickdown is just throttle to the floor but you don't get any notification from the pedal, the point of the resistance is so you can't activate it by accident.

12-09-2007	#1 (permalink)
geermx SLK World Member Join Date: Dec 2007 Location: Phoenix, AZ Vehicle: 2005 SLK350 w/ AMG Posts: 11 Country: Thanks: 0 Thanked 0 Times in 0 Posts	Gas Pedal Travel I've noticed that when pressing the gas pedal it travels to a stopping point and then with added pressure goes beyond the initial stopping point. It almost feels like a pressure sensitive switch. Has anyone else noticed this and if so what is the purpose?

12-09-2007	#2 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,794 Country: Thanks: 96 Thanked 225 Times in 177 Posts	That would be the resistance spring for Kickdown __________________ One thing you will learn with German cars - If it's simple it ain't happening.

12-09-2007	#4 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,794 Country: Thanks: 96 Thanked 225 Times in 177 Posts	Sure no worries. If your car is a manual then this does not apply. Kickdown is activated when the pedal value reads over 100%, the ECU (engine control) reads that value and sends a message to the TCU (transmission control) saying that you want full acceleration. This causes the transmission to shift into the lowest possible gear for the current engine speed, as soon as it confirms that has taken place the ECU opens the throttle fully and the car will run to its redline then shift right up to the maximum engine speed in the highest gear then when you ease off of the pedal the car returns to the state it was in before kickdown was activated (or as close as possible). As i say this has no effect on a manual but the spring is left installed so Merc only have to produce one throttle pedal for the car. __________________ One thing you will learn with German cars - If it's simple it ain't happening.

12-09-2007	#6 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,794 Country: Thanks: 96 Thanked 225 Times in 177 Posts	Yep thats true, and most electrically operated manuals have it also __________________ One thing you will learn with German cars - If it's simple it ain't happening.

12-09-2007	#8 (permalink)
DansSlk Dude Join Date: Jun 2006 Location: Wales Vehicle: 05 B55S (Brabus 6.1 S) Posts: 6,794 Country: Thanks: 96 Thanked 225 Times in 177 Posts	Not all vehicles have the detent so in some kickdown is just throttle to the floor but you don't get any notification from the pedal, the point of the resistance is so you can't activate it by accident. __________________ One thing you will learn with German cars - If it's simple it ain't happening.

12-09-2007	#3 (permalink)
geermx SLK World Member Join Date: Dec 2007 Location: Phoenix, AZ Vehicle: 2005 SLK350 w/ AMG Posts: 11 Country: Thanks: 0 Thanked 0 Times in 0 Posts	I apologize for not knowing what that is or what it's purpose is, could you elaborate?

12-09-2007	#5 (permalink)
mtiede Founding Member #7 Join Date: Jun 2006 Location: Western New York Vehicle: 2006 SLK 350 Posts: 1,645 Thanks: 102 Thanked 55 Times in 45 Posts	One additional point. This is not a feature unique to MB, but, as far as I know, all automatic transmissions have this feature. Move to the passing lane and floor it

12-09-2007	#7 (permalink)
geermx SLK World Member Join Date: Dec 2007 Location: Phoenix, AZ Vehicle: 2005 SLK350 w/ AMG Posts: 11 Country: Thanks: 0 Thanked 0 Times in 0 Posts	Interesting... I guess I never noticed it before, but then again I don't remember flooring my Explorer.

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