yabloky

Hi all.

Yesterday I was driving down the highway and noticed that when I release the gas pedal, the car quickly loses speed, even if it goes down a slight hill, it feels like the engine brakes.
Attaching a video, who owns a GLE v167 350 4matik, can you tell me if this is normal or not? And in what direction to dig?

MBguy013

What options does your 350 have? Do you have Distronic? Even if you don't, I think the basic vehicle safety features, like emergency braking, will automatically slow you down especially if there are vehicles in front of you or if you're going downhill. I do not believe this is an issue unless you're saying it's extremely aggressive but then again, safety features.

yabloky

I don't have a distronic, and exactly the same situation happens on a completely empty road and the strangest thing when driving downhill, the impression is that the engine or transmission brakes ... even when I drive in ECO mode and it shifts to a neutral speed, still something brakes.

It doesn't feel like brakes, the wheels are spinning fine I think.

ddeliber

Check your RPMs and what gear you are in while coasting like this. When you take your foot off the accelerator does it shift? If it is engine braking RPM will probably be above 2k and decreasing slowly (obviously dependent on speed) . You can also try upshifting with the + paddle shifter while coasting to see if that changes the feel. At least you'll know if the transmission is slowing you down when you don't really want it to. In comfort and eco it really should upshift automatically (sometimes few gears at higher speeds) .

yabloky

would you mind watching the video I attached to the first post? There you can see how fast the speed drops without the gas pedal and revs and gears, I just do not understand it ((

ddeliber

Yea, I should have checked that before I posted. It is in 9th the whole time so it isn't an aggressive transmission. It did look pretty flat so I am not sure how quickly it really should decelerate. From 140km/h ish to 100 or so in 25 seconds isn't really that surprising. There is a lot of aerodynamic drag on a SUV at those speeds. My gut says it looks pretty normal. Areas that may affect this are tire pressure, drag (windows open, roof rails etc), a tight wheel bearing (not likely) etc.

Not sure what year your GLE is but it probably will go into glide/sail mode when in Eco (Green surrounded D instead of D9) this would give you an idea how much the gearing is affecting deceleration because when "gliding" it basically shifts into neutral.

yabloky

2019, exactly the same picture on the planning. And the engine is a weak 2.0, maybe that's okay, just wanted to hear some opinions

superswiss

Looks pretty normal. What were you expecting and what are you comparing it to? Yes, there is engine braking. As long as the transmission is in gear and you take the foot off the throttle the engine will slow you down as the fuel delivery is cut off. In 9th gear the effect is the smallest because of the high gear, but the engine will still slow you down. Completely normal. Then as said above, an SUV has the aerodynamics of a shipping container. Huge frontal area compared to a regular car. and even worse compared to a streamlined sports car, so all that air you are pushing along in front of you will slow you down.

Also, I see you are in Europe. What GLE 350 do you have exactly? At least on the German configurator I only see the GLE 350 de, which is a hybrid diesel. So if yours is a hybrid, then when you take your foot off the throttle there will be energy recuperation, which will slow down the car while converting your kinetic energy into electricity and stuff it into the battery.

EDIT: Forgot to mention Efficiency mode. If you put DYNAMIC SELECT in Efficiency mode, then when you take the foot of the throttle above certain speeds it will enter glide mode, during which the transmission is decoupled from the engine and the car with glide under its own momentum and only losing speed due to aerodynamic drag and the remaining friction in the drivetrain, but there will be no engine braking.

yabloky

Thank you for your comprehensive answer.
I have an American version of the GLE 350 v167 4matik, it's not a hybrid or diesel - it's a turbocharged 2.0 gasoline.

This is my first Parkett, I've driven sedans before, so nothing to compare it to.
I thought it should somehow take longer to coast. I mean, don't go to the dealer to check and just drive in eco mode on the highway?

yabloky

And why when I release the pedal at 140 - the speed drops quickly, and if the speed of 100, then slowly?

jtjbt20x

It's completely normal. The speed loss is faster at 140 because the air drag is higher at higher speeds, plus the mechanical energy loss in the drivetrain is also higher at faster speeds.

yabloky

Too bad, I thought it was possible to do something and roll longer saving fuel )

wildta

At least you'll save on brake wear. 😉

ddeliber

You can. Put it in eco mode and the car will "glide" disengaging the transmission allowing it to roll free.

yabloky

I switched, also loses speed quickly. Here's a video.

ddeliber

Yea, that looks normal. At 130 km/h it will slow faster simply because of aerodynamic drag (washing machine analogy from previous comments) It is also a perfect example showing that the car detects slower moving traffic a couple seconds after it starts. She switched from "glide" to D9 when you approached the truck and then went back into "glide" after the truck changed out of your lane. While in D9 I expect your GLE to have decelerated faster than when it was gliding. Did you notice the change?

yabloky

So I'm just not used to driving SUVs and comparing them with sedans)

superswiss

Because speed is the biggest factor. The drag force is proportional to the square of the speed. Below is the drag equation. In simple words, if you double the speed, the drag force quadruples and not just doubles. The other parts are liner, but as you can see the higher the drag coefficient times the frontal area, the higher the drag force. Both of these are higher on an SUV than a more streamlined and lower car.

EL-34

It's normal. That's when the engine is running under vacuum and the engine brake occurs.

BlueYonder

You can see the motor downshift in the video, it doesn't look like it is coasting. It also starts to slow more rapidly when a truck pulls over in front of you. Are you sure the distronic is turned off? Regardless, I wouldn't be concerned. You can always just put the transmission in neutral and see how the vehicle slows then.

yabloky

I don't use the distronic at all
I'll try to put it in neutral when I'm on the highway.
Maybe some new firmware needs to be flashed on the car?

Is there nothing you can do about it? What if it slows down smoother?

MBguy013

As many have said, things appear to be normal. You can always take it to the dealer and ask them to verify.

EL-34

consider it as a sign of a very healthy engine and transmission. The piston rings are seated properly. Our 450s are 6600 lb beasts.

i have a 11 year old volvo xc60 (also inline 6, 3L turbo but only 4000 lb) and when the oil is fresh it really slows (engine brakes) when coasting. It's 2000 pounds lighter.


the trans takes a while to adapt just like any new car. Trans flush every 60k miles. Oil change every 5k miles.

Plus the 450 has the eq boost thing that takes energy from coasting to charge the battery.

yabloky

I have a regular 350 4matik )
Without EQ boost )
But I get the point. I just thought that the car should not so obviously turn nose when you release the gas pedal, and somehow smoother it all should happen, but if it is so for all - then it's okay.

W205C43PFL

As others mentioned, aerodynamics (or lack thereof) of the SUVs is one of the cause, tires (like winter tires just as an example, I understand you don't have) is another cause.