C43 stock/sport exhaust question
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Joined: Nov 2016
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From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Pops and bangs and such are not generated by the exhaust. They are generated by the engine ECU by changing the ignition timing. Specifically, the combustion is extended past the cylinder exhaust valves opening, so fuel burns inside of the exhaust causing the pops & bangs. Sport+ also raises the idle rpm, so making things louder even at idle and you are generally in lower gears and at higher rpm in Sport+.
Is there a Mercedes tech bulletin or other document that describes how the pops, bangs, crackles, etc. work on AMG cars?
Out Of Control!!
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From: San Francisco Bay Area
2019 C63CS
Are you saying that these mini-explosions are a result of adjusted timing of the exhaust cam/valves? If so, where are the explosions occurring? Before the turbo? I'd like to read the technical documentation that describes what is happening. I know they sound cool, but they still seem destructive.
Is there a Mercedes tech bulletin or other document that describes how the pops, bangs, crackles, etc. work on AMG cars?
Is there a Mercedes tech bulletin or other document that describes how the pops, bangs, crackles, etc. work on AMG cars?
Joined: Nov 2016
Posts: 7,847
Likes: 3,498
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Interesting. So, during the power stroke the exhaust valves are opened "prematurely" to decrease the force in the cylinders during deceleration. That certainly makes sense since you are decelerating and don't need power. That is definitely not how "traditional" pops, etc. are generated. Is this approach only for turbo cars? I wonder if that is how tuners also are able to add crackles and pops to their tunes. I would be far more comfortable with that than having small explosions in the exhaust stream.
Out Of Control!!
Joined: Nov 2018
Posts: 11,480
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From: San Francisco Bay Area
2019 C63CS
These pops only serve a technical purpose in turbo engines. In naturally aspirated engines it's basically unburnt fuel burning in the exhaust, or misfires, but somehow it entered mainstream and everybody thought pops&bangs were cool. I've said this before, to me it sounds like the engine has a problem and is misfiring. I do understand the anti-lag nature, but that's only needed if you are actually driving aggressively, not when just tooling around town at 25 mph.
Junior Member
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From: Finland
Non PE and PE cars alter exhaust valve timing to get deeper rumble on idle and city driving.
at around 4000rpm its reverting to more efficient timing as there is already enough noise naturally from the engine
You can observe this by logging exhaust cam timing on normal, sport and sport+
at around 4000rpm its reverting to more efficient timing as there is already enough noise naturally from the engine
You can observe this by logging exhaust cam timing on normal, sport and sport+
Junior Member
Joined: Jan 2025
Posts: 30
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Non PE and PE cars alter exhaust valve timing to get deeper rumble on idle and city driving.
at around 4000rpm its reverting to more efficient timing as there is already enough noise naturally from the engine
You can observe this by logging exhaust cam timing on normal, sport and sport+
at around 4000rpm its reverting to more efficient timing as there is already enough noise naturally from the engine
You can observe this by logging exhaust cam timing on normal, sport and sport+
Thanks in advance!
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Junior Member
Joined: Oct 2024
Posts: 52
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From: Finland
Deeper rumble / more exhaust noise.
a deeper note to the exhaust as the exhaust valves are opened little earlier.
It is slightly less efficient and you can observe this with driving the same route for a week in manual mode Sport+
and then the same route one week in manual mode comfort
Sport+ consumes a liter or more /100km fuel in the same route than comfort.
Even when shifting at the same rpm and driving similarly every day.
a deeper note to the exhaust as the exhaust valves are opened little earlier.
It is slightly less efficient and you can observe this with driving the same route for a week in manual mode Sport+
and then the same route one week in manual mode comfort
Sport+ consumes a liter or more /100km fuel in the same route than comfort.
Even when shifting at the same rpm and driving similarly every day.
Junior Member
Joined: Jan 2025
Posts: 30
Likes: 4
Deeper rumble / more exhaust noise.
a deeper note to the exhaust as the exhaust valves are opened little earlier.
It is slightly less efficient and you can observe this with driving the same route for a week in manual mode Sport+
and then the same route one week in manual mode comfort
Sport+ consumes a liter or more /100km fuel in the same route than comfort.
Even when shifting at the same rpm and driving similarly every day.
a deeper note to the exhaust as the exhaust valves are opened little earlier.
It is slightly less efficient and you can observe this with driving the same route for a week in manual mode Sport+
and then the same route one week in manual mode comfort
Sport+ consumes a liter or more /100km fuel in the same route than comfort.
Even when shifting at the same rpm and driving similarly every day.
One would think the slightly higher fuel consumption in Sport+ is because of the high rpms in idle. But I really don’t know :P
MBWorld God!
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Ah, I see! Correct me if I misunderstand, you’re saying that only at around 4000rpm and beyond will the engine’s fuel efficiency be similar in both comfort (PE valves closed) and Sport+ (PE valves open)? That is really interesting!
One would think the slightly higher fuel consumption in Sport+ is because of the high rpms in idle. But I really don’t know :P
One would think the slightly higher fuel consumption in Sport+ is because of the high rpms in idle. But I really don’t know :P
