While in sport mode.....
Thread Starter
Member
Joined: May 2020
Posts: 180
Likes: 17
From: New York
2025 e450
While in sport mode.....
Is it normal while in sport mode for the transmission to rev so long after removing foot from gas? I don’t know if I’m explaining it right. For example.... light turns green and I step on gas.... I get to about 35-40MPH and I see the next light is red. I remove foot from gas and apply break but it still revs (not sure if right word) loud and long till just about I completely stop. ( light to light around 1/4 mile).
*** 2020 GLE 350. 750 miles
*** 2020 GLE 350. 750 miles
Out Of Control!!
Joined: Nov 2018
Posts: 11,651
Likes: 5,470
From: San Francisco Bay Area
2019 C63CS
It's called rev hang and it's a characteristics of modern cars. Suddenly letting off the throttle causes the fuel air mixture to go rich, which is very bad for emissions, so the ECU delays the throttle closing to let all the extra fuel burn off normally. Turbo charged engines are more prone when under boost, because all the additional air from the turbo charger requires increased fuel injection and then when you suddenly take your foot off the throttle while the engine is under boost there is too much fuel in the intake manifold and it has to burn that off first. Sport etc. makes it more likely that the engine is under boost, so it may be more pronounced. Best way to avoid it is to smoothly let off the throttle and let the boost disappear before completely letting off the throttle. If you are accelerating and then suddenly have to let off the throttle, you'll get rev hang.
Thread Starter
Member
Joined: May 2020
Posts: 180
Likes: 17
From: New York
2025 e450
It's called rev hang and it's a characteristics of modern cars. Suddenly letting off the throttle causes the fuel air mixture to go rich, which is very bad for emissions, so the ECU delays the throttle closing to let all the extra fuel burn off normally. Turbo charged engines are more prone when under boost, because all the additional air from the turbo charger requires increased fuel injection and then when you suddenly take your foot off the throttle while the engine is under boost there is too much fuel in the intake manifold and it has to burn that off first. Sport etc. makes it more likely that the engine is under boost, so it may be more pronounced. Best way to avoid it is to smoothly let off the throttle and let the boost disappear before completely letting off the throttle. If you are accelerating and then suddenly have to let off the throttle, you'll get rev hang.
Out Of Control!!
Joined: Nov 2018
Posts: 11,651
Likes: 5,470
From: San Francisco Bay Area
2019 C63CS
Correct, nothing to be concerned. It's a bit annoying at times, so you'll have to get used to it and try to avoid it by easing off the throttle.
