gholland

Hello

I very much enjoy my GLC300, it's my first foray into the Mercedes world. It is also my first experience with a turbo, my other cars have been normally aspirated. I would like to know if there have been solutions discovered to the turbo lag from a standing start. All other aspects of performance I like and enjoy the car. I have searched the 'net and this forum and have come up with not a lot that is a solution but figured I'd check.

Thank you!
gh

bips

Same here. My wife makes the same observation with her newish B200. It seems to be the price you pay to balance performance and economy. You get used to it. You learn to anticipate it by taking your foot off the brake earlier. Sport or Sport+ mode helps. The one situation where it remains an issue is in trying to take advantage of a small gap in oncoming traffic, where you really need to anticipate and move early to offset the lag, perhaps with the aid of Sport+.

Ddmccormack

I don't really notice the lag, frankly. I believe turbo kicks in at 1700 rpm, not sure.

Roowah

Interestingly, I noticed the lag as well, usually when at a stop and need to move quickly to merge into traffic. I mentioned this to my SA, and while doing a software update told me that the transmission learning mode was reset as well. There was a marked difference in response time with no lag, even in comfort mode.

I wonder if there's a way to reset the transmission without having to do a software update? I remember my BMW had a few hidden menu screens where you were able to tinker with some things.

decorily

I believe there is a simple procedure. ....but I can't recall exactly what it is!

Involves switching ignition to on without starting the engine and pressing and holding accelerator or something simple like that! !
Will post if I can find it.

fabbrisd1

Frankly the "lag" most people mis-identify as turbo lag - is the automatic transmission as it has to sense what to do for downshift..

Everyday driving - switch to Sport and drive a week - then switch to Sport+ and drive a week - and see which profile Comfort-Sport-Sport+ fits you best.

On a "demand scoot power now" - pull/hold left paddle for 2 1/2-3 secs which takes you to power gear for the speed - then to go back to automatic pull/hold right paddle to get back

bips

But from a standing start, which is what my comments were mostly about, surely any delay is turbo lag? That's when I mostly notice it, rather than in general driving.

The thing about switching to sport or sport+ mode is that a number of things are changed. My impression is that it's not just the gear changes that are different - the drive-by-wire throttle is programmed to be more responsive and I suspect that the turbo also behaves differently, so it's a package of things, isn't it?

ItalianJoe1

If you go full throttle, is the delay still there?

I tend to notice, in comfort settings, the pedal is very delayed, when you step down a little, nothing happens. It is set up to maximize fuel mileage and economy. If you punch it hard and the pedal value changes quickly, it is more urgent, but not as much as sport/sport+ response.

bips

My salesman told me that if you go full throttle, as in push it quickly to the floor, there is a switch is activated that changes the engine's behaviour. He said this to me after I observed that when looking to pass a car on country road when in economy mode I briefly switched back to sport+. He pointed out that there's no need to do this - just go full throttle. Seems to work. But I'm not sure that I'd do this in the city, when trying to pick a gap in oncoming traffic.

ItalianJoe1

There's a "kickdown" switch, a term from the old days when it actually was directly connected to the transmission and controlled downshift behavior. You can feel it, push the pedal down with the engine off. As you reach the first stop, push a little harder. You feel a click and the pedal drops a tad further. For now, it is just as you described, if you push the pedal all the way down, the ECU knows you are serious and delivers maximum acceleration as soon as possible.

If you are trying to squeeze into a gap, floor the pedal. It will downshift fairly fast and give you all the power you need. If you aren't giving full throttle and it feels slow, just give it more throttle.

bips

Kick-down switch may be the term my salesman used. I have no trouble using it for overtaking at cruising speeds. I am a little wary of using it in the city at one right-hand turn (left hand turn in the US, Canada and Europe) across three lanes of busy traffic, as I need to enter my lane on the other side of the road with some semblance of control. I will give it a try, when it seems to be low risk.

ItalianJoe1

The car isn't gonna fly off the road, just accelerate at it's best performance possible. You still have traction control and stability control active all the time, and those systems see that you're turning the wheel and act accordingly. It's actually surprising just how much performance you can get out of a modern car when you just push it and let the electronics do the work for you.

bips

The phrase "some semblance of control" was only really a reference to control over speed. I wasn't suggesting that the would spin out of control, only that I didn't want to enter my lane at too high a speed. I guess it's only a 250d, not an AMG 43 or 63.

ItalianJoe1

Well when you reach your desired speed, simply lift off the go-pedal and cruise. But a solid initial hit will remove most of that 'delay' the cars have on initial take-off.

gholland

Great discussion! My question at the top was about the 1/2 second delay from a standing start, this is my first turbo car and I'm not familiar with that delay. My understanding is that the turbo needs to spool up as it relies on engine exhaust and then it gives you the boost. In my searching I see plug in devices that claim to amplify the throttle response so it reduces the lag but then I read about how if you simply mash the throttle to the floor it does the same thing. I then read about 'ECU resets' and I'm wondering if there is something in the programming of the car that might be adjusted.

thanks!
gh

vratenza

IIRC, the hp/torque graph of the GLC, the max torque comes in at 1200rpm and totally flat till it drops off 4000rpm...which is an amazing feat for any car outside of the electric/hybrid club. The idle rpm being around 800rpm, that is just 400rpm from idle. Most modern day 2L 4 pot turbos have their max torque coming in only at 1700rpm there abouts.

vratenza

This is an interesting feature! I did not realise there is a hold function to the paddles.

Sigp232

Thought the slight delay was from starting from 2nd gear

Roowah

That's an interesting point. If in Comfort or Eco mode, the transmission is in 2nd gear at a stop. Since 2nd is a taller gear than starting in 1st (as it would in Sport or Sport +) , it would make sense that the initial response would be a bit sluggish.

I wonder if you're in Comfort at a stop, whether there's a way to have the transmission recognize quickly it needs to downshift besides physically using the paddles or flooring it? As I mentioned earlier, my transmission's learning mode was cleared last time I was in, and I saw a difference in response time for awhile.

Sigp232

Drove around town today in S mode and it does seem a little bit more responsive from 1st gear. Or it could be my imagination. But will try it again tonight after visiting my local bar for a couple of Black Russians.

ajmtbm

S definitely seems much more responsive to me. and S+ even more so.

the first 1,000 miles on E were painful - makes the car feel sluggish

i typically drive in comfort mode and during normal driving i dont really notice the turbo lag - though in regular driving i admittedly do accelerate rather slowly and smoothly.

decorily

Not in my 250d. Starts from a stop in 1st gear in every mode.

Roowah

If that's the case, it could be a transmission programming difference between gas and diesel engines.