Jadis

I don't usually drive in Sport+ mode (normally I use Sport Mode) but today I noticed that under hard acceleration when shifting gears, in the lower gears (like going from 2 to 3) there is a noticeable "fart" or "burp" noise (I think coming from the exhaust?). Kind of like the sound some motorcycles make sometimes.

This doesn't happen in Sport or Comfort mode.

Is this normal or expected? Bad or good thing and why might it be happening only in Sport+ mode?

Mike5215

Ha! You're gonna make the C450 guys weep. So that sound is known as a "crackle" and it occurs when unburned fuel is allowed to enter the exhaust, where it spontaneously combusts. It's very prominent in the C450's AMG tuned exhaust in Sport + and most owners love it, but there's been reports of C450s suddenly ceasing to crackle. This is pissing the 450 guys off, since it's a part of the car's character.

Meanwhile I'm gonna try to get my C300 to do it tomorrow!

Jadis

Hmm interesting. Still, why doesn't this happen in Sport mode under similar hard acceleration (approaching the red line, but don't need to necessarily reach the redline).

It ONLY happens in Sport+ mode.

I can do it at will from either a stop or starting at low speeds in the lower gears like when I speed up on the highway entry ramp.

Mike5215

In the C450 at least it's an intentional part of the Sport + tuning map. It's a feature, not a bug. Not harmful to the car. I guess MB only wanted it on the most aggressive driving program. How are you liking your C? Fun little car, right?

Jadis

I still love it even after almost a year of owning one as a daily driver. Great balance between comfort, luxury, sportiness/power.

gfmohn

Has anyone seen any performance figures that prove that Sport+ is actually faster than Sport?

ManiacGT

None of the modes make the car faster, they simply change shift points steering weight etc to make it feel different.

janusgrimnitz

its just a firmware feature.. my c200 does it too... sounds cool especially with windows down.. hahaha

xMB007x

I feel the car is fastest in sport mode. I'll use sport+ only if I want to make that pop noise. I noticed it does it when the car is under full boost and you shift around 4-5k rpm.

Mike5215

It's just starting in a lower gear and it holds upshifts longer. Makes the throttle feel more responsive but no actual change in power or torque.

StanNH

I fart in sport mode too. My wife finds it very annoying.

DapperStyle

Sports+ is exactly that it is Sport mode PLUS, gives you extra oomph when driving your car spiritedly. It's totally normal and will ONLY happen in Sport+ along with even harder gear shifts and more engine braking.

As others have explained it has to do with gearing. Sport+ will help the car stay within the power band giving you quick access to torque/hp when driving spiritedly.

DapperStyle

Removed from the 2016 C300 unfortunately and as I have a 2016 loaner right now I can confirm the fart is gone, I am going to make a thread about it now for everyone to see.

Mike5215

Yeah my 16 refuses to fart.

INS1GNIA

I think I'm doing it wrong....

CO2010

It's a C class. Not a Lamborghini Aventador. It shouldn't make any "Farting" noises.

ManiacGT

Yes it should, it's a feature of earlier builds as mentioned above.

Tobby

My 2016 C180 CGI makes that farting sound in Sport+ too

CO2010

I typically don't drive in any other mode other than Sport+ and I have never heard any snap, crackle, or pop in over a year of ownership. I would love for someone to post a sound clip.

DapperStyle

Try it in manual mode, shift to 3rd near 5000-5500 RPM and you should hear it go off.

ManiacGT

If you've ever heard DSG equipped VWs such as the golf R it sounds just the same.

Like this:

Str8Down

That noise is not un-burnt fuel in the exhaust. Its the blow off valve from the turbo venting into the airbox. If you vented it to atmosphere, it would make a "PSSSHHHHH" noise, that I assume Mercedes didnt want in a non-sports car, so they vented it back to the airbox to quiet the sound.

xMB007x

Yes I know that but I'm not a fan of the way it changes gears as it feels like it chokes when it shifts. I feel sport mode shifts faster & smother than sport+. To me the only benefit for sport+ mode is the pop sound.

DapperStyle

Sport+ is designed to shift harder. It's not supposed to shift smoothly at all.

LateC300

what? no

this happens to most cars now that have a decent tune on them or an exhaust that's loud enough to hear it. it has nothing directly to do with a turbo...

watch at minute 1:44

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