Sheepy

Manufacture date of April 2015.


When in Sport + mode and accelerating hard, the car ****s from second to third fairly quickly. It's not a hard shift but it is more noticeable than when changing from any other lower gear to the next. It also gives off a short and distinct "gurgle" sound. At first it sounded like the gurgle you hear in a C450 but this car shouldn't be capable of making that noise.

I do not hear any engine knocking sound when accelerating. Gears do not drop out. Etc.

Thoughts? If I need to get it looked at what should I tell the dealership?

20k miles.

DapperStyle

Okay I started out writing an incredibly dickish reply regarding this but decided against it.

Long story short, it is normal. Please use the search regarding this feature if you require more information.

kowyzg0moo

You're one of the lucky few who have that cool sound. They removed it from all cars after August 2015 production I believe to differentiate from the C450/400

chicago-guy

I've got the same build date. I get the pops between at least two gears (per "test" today). I happen to like them (favorite moment: it turned a very surprised head in an Audi RS5 convertible I was keeping pace with away from a light), but maybe not to everyone's taste.

The problem with finding all the relevant threads in the forum is that there isn't agreement on what to call the sound. Some say bark, others gurgle, others fart (not a fan of that one personally). But bottom line for me is I agree with @kowyzg0moo that we're lucky to have that feature, if not for personal enjoyment then as potential icing on the cake for a future buyer?

Also lucky with this build date in that you should avoid the threat of MB-Tex sealant turning glossy/cloudy, since that problem was apparently resolved as of 1/2015 builds (per a different, lengthy mbworld thread) -- assuming you don't have leather. If you have leather I guess you're triple lucky. Cheers

Sheepy

Thanks for taking the high road.

I only ask because I was about to pull the trigger on the 450 and someone mentioned on this sub that the C300 will never burble when shifting. :P


I was recommended several times that if I do go for a C300 then make sure it is April 2015 or later. Pulled the trigger on this one because it was an outstanding price and had the right born on date.

Mike__S

I am pretty familiar with these types of sounds in turbocharge cars.

There are two possibilities. I have not heard this sound and it depends on MB approach to turbo lag. A turbocharger compressor stalls when the throttle is closed. Because of this compressor stall, it takes a second or two for full power to develop again. The following two features are used in many turbo cars.

The first road car to feature a priority valve was the 1988 Porsche 944 Turbo. The next turbo car to use this feature was the 1989 the Subaru Legacy RS and following 1993 Impreza WRX, which used the same engine. Several, but not all, later turbo cars have used this feature. It greatly improves throttle response.

Many road going performance turbo engines, Audi, Porsche, Subaru, etc) have a priority (compressor by-pass) valve that links the compressed air intake side of the turbo compressor to the atmospheric side or intake. If the intake pressure at the throttle goes negative through a easing (lift-off) or complete closing of the throttle, this vacuum opens and dumps compressed air back into the low pressure intake side. This prevents the turbocharger compressor from stalling (loosing its ability to pump air)

To understand this effect listen to a vacuum cleaner motor spin free when your hand is placed over the nozzle. Doing no work (pulling a vacuum, but moving no air) the motor RPM audibly increases. A similar 'free wheel' effect takes place using a priority valve. There is a sometimes audible 'whoosh' changing gears.

In the late 1990's it was very cool to install an aftermarket external "bow-off" valve that dumped to atmosphere (of course, technically a totally dumb idea) and therefor make a huge noise. These open circuit compressor by-pass valves are to prevent blowing open seams or blowing off hoses in very boost engines, but this is a ultra-hi boost or pretty much a race car problem. The first modern race car to have this high boost problem was the Porsche 917-30. It made a huge chirp! sound every gear change as four blow-off valves opened and closed. Loud flat-12 engine sound, abrupt silence immediately followed by an equally huge chrip and the flat-12 sound came back on line. With 1500hp in hand, one did not just slam on full power after a gear change. You applied the power gingerly.

The advantage of a priority valve for the road car is marked throttle response improvement. The priority valve return is spring loaded, so it does not snap shut, but closes somewhat slower, allowing the compressor to spin up when the throttle is opened again before load (the complete closing of the valve) is applied to the compressor wheel again. This is a matter of .2-.3 second delay. It greatly reduces turbo lag in general and power loss during up shifting, even at part throttle settings.

The other, and more probable cause of the sound is the fact that quick shifting automatic gearboxes in race and rally cars simply cut the ignition, leaving the fuel on during an up shift. This time period is only the .1 or .2 seconds it takes to unload the gearbox and load it up again.

The shift complete, the ignition turns back on. There is a bit of raw fuel by this time in the turbine housing and exhaust pipe. There is a decided 'chuff' or blurb sound as this excess fuel in the exhaust ignites. This rapid expansion of gas in the turbine side spins up the compressor to full boost again.

Such a feature is also known as anti-lag when it operates under extended periods of closed throttle in a race car or rally car. In passenger cars this feature is not used except as a very minimal application only during upshifts. The principle is the same.

Leave it to Americans to complain about the odd noise instead of appreciate the greatly improved throttle response. Thus, since about 2004 Audi, BMW and Mercedes have all but eliminated this feature on their regular (not high performance) passenger cars. It is coming back now that there are separate Economy, Normal and Sport modes in the various turbo models. I am saddened to hear is was eliminated even in Sport mode on the C-Class.

Anti-lag and related turbo control features were first developed for WRC Group B rally cars about 1985(?). The flames chirps and pops they made or the huge flames shooting out the exhaust of sports racing cars are due to these throttle response improving features.

Sheepy

No worry, I do enjoy the noise.

Wkar275

Any way to get this throttle blip added in to a 2016? Perhaps the 2015 ecru has it? I know aftermarket tuners are able to do that with other cars.

chicago-guy

Really appreciate your in-depth exploration of this @Mike_S, and it makes me curious which of the two explains the 2015 C300 pop. Seems logical to me that turbo lag is being eliminated somehow (and I do remember what that lag is like, domestically from as far back as the turbo four-banger optional on mid-80s Chrysler/Plymouth Lasers, LeBarons, New Yorkers, Caravelles, and even the occasional Reliant). But if the pop/burble sound relates to lag-reduction, then I wonder what the 2016 C300 engine is doing -- in sport-plus -- to handle that issue while stifling the pop that the 2015 engine gets? Is it being muffled? Is performance slightly reduced vs. the 2015? Or is the 2015 C300 pop just a simulation that doesn't relate to performance at all? Anyone got the goods on this issue?

janusgrimnitz

does it sound like this ?

alexasa

iTrader: (1)

This is called a shift fart.

Pretty standard.

The C450 will have exhaust backfire when easing off the throttle above ~3.5/4k RPM.

The C450 also has the shift fart, but that usually isn't adored or sought after. I feel like all the people bragging about it just want more noise from the exhaust and like to justify their purchase with irrationalities.

Just because a car farts does not mean it sounds good.

Mike__S

Just thinking about it, the burp or burble is probably the fuel being left on during upshift, although it has a by-pass valve as well. The latter is more a quieter, whish sound that you really have to listen for.

Usually manufactures will not upload older firmware. However, you could ask the lead mechanic at the dealer. (don't ask a service writer, they are generally clueless on technical details, unless you are very lucky)

Most likely removed due to owner complaints. 2007 Audi and VW took it out of the DSG turbo cars for that reason. It is another sign of the times.

Maybe an aftermarket tuner chip is the way to go? They would leave it in for sure. I'll just leave it at that. There are tuners, then there are the real guys, far and few between.

Sheepy

No no, it's more "guttural" than that.

LateC300

ugh, that's terrible. a sure fire way of making your benz sound unrefined and obnoxious as hell.

standard manufacturer "farts" sound better, except the new C43's with the active exhaust. too much.

ManiacGT

This noise is only present in sport plus on my C200 and is usually accompanied by a rather uncomfortable jolt through the car. It might sound good but I'd bet good money it actually makes it slower as the jolt on mine feels like I hit the brake for a fraction of a second.

the gearbox is frankly complete pants

Mike__S

A manumatic or now the good, quick shifting, lock-up automatic gearboxes are on average a full three seconds a mile faster than a manually shifted gearbox. That alone is enough reason to use DSG, SMG, TipTronic or what ever these days. And, in sport mode they shift HARD!

Plus, we have the small to medium turbo motors everywhere now with their own set of tricks. The jolt is full power coming back in on the turbo motor, i.e. no lag anymore and a lot more torque than normally aspirated motors after the gear change. Exactly as intended. If you do not appreciate it, just leave it out of sport mode setting. This phenomenon is just a part of the manumatic/turbo motor technology story.

Your body unloads the +G at the instant of the shift and instantly get reloaded to +G on the power take up. This is not slower, what ever you may imagine.

Some modern road cars are so quick and positively violent they will scare normal people sick or silly, usually sick if driven full to the limit. Trust me, I have personally caused this to happen several times, including once a race queen passing clean out. Audi R8, Corvette Z06, Porsche Turbo or GT3, and the various exotics are the prime suspects. Using similar technologies, even our ordinary luxury cars can present some shadow of this edginess today as well, yet are tempered by virtue of the Dynamic Drive mode switch settings. And then we complain about it? Yawn.

Sheepy

When my C300 is in S+ it shifts rather hard, but that's what I was expecting. That and some slight compression drag/jerk when taking my foot off the pedal/first accelerating.

ManiacGT

I have a BMW N54 car with DCT, I know what a hard shift is like and what its supposed to feel like.. a kick in the back as it powers into the next gear at max torque.

That is NOT what I get in the C200 with its crappy ancient slush box. Quite the opposite, even when driving normally it jerks between gears on any low gear shift that is more than 20% throttle. In sport plus it shifts worst of all with what feels like brakes being applied before kicking into the next gear. With the snort from the exhaust and a knock from the drivetrain. Its not like a manual where you feel the loss of G, its like that plus brakes being tapped. Its quite possibly the worst auto car I've ever driven and I've driven quite a few over the years. None of this issue in diesel C's I've driven, seems unique to the handful of 4 pot petrols. Def a poor gearbox and engine match. There's a lot of people complain about it. Its the single reason the car will be going back and not a keeper.

Mike__S

Sorry to hear the fresh details on this one. Bummer. The 7 speed is not a bad gearbox over the years. Strong as an Ox, for one thing.

That does sound like a build problem in the transmission. Possibly sticking clutch plates on the planetary gear sets. Such a problem would give that type of feeling on gear changes.

But a lot of people? Like 200-300? Out of how many cars sold? Subaru had a problem with 5th gear synchro over heating on the wide 5th/6th gear STI boxes used in USA and Australia. 5th gear synchro would no work when hot. Everyone that had the problem was complaining, and that was a goodly pile of about 600 boxes made with an improperly machined part. An automated lathe had a tooling failure that was not caught one evening making this part. That is all it takes. They did not take the cars back, just replaced the gearboxes.

I imagine there may have been a similar tooling/machining problem, or like their upholstery supplier, the supplier of the clutch plates was not paying attention to QC. A bit scary some of the defects in materials that have come through the line on these cars.