Power throttling at high speeds
2017 Mercedes-AMG C43 Sedan (~2,300 km/~1,400 miles)
Modifications:
Eurocharged v3.0 performance engine software, K&N air filters, ASR exhaust flap control
Nature of the issue:
I recently purchased a Dragy GPS performance meter and performed a few runs to test the performance of my C43. I had the oil changed just after breaking-in the engine and this is the first time I've really ran the vehicle hard from a stand-still. The issue that I'm experiencing is that, when I reach ~165 km/h (~105 mph) during full-throttle, the engine reduces power and it feels as if I'm easing-up on the gas pedal. This is substantiated by information on the "Engine Data" menu on the infotainment system as it drops from maximum power to ~270 hp. What is strange is that this issue only occurs if I run the vehicle hard from a stand-still. If I'm cruising at ~100 km/h (~62 mph) and go full-throttle, I can reach speeds >200 km/h (~124 mph) without experiencing a power reduction. I brought my C43 to the Mercedes dealership this morning and they ran a full diagnostic check via their Xentry system and found no issues or stored fault codes and she shop foreman performed a reset of all systems; however, the issue still persists. According to Dragy, the performance is where it should be for this vehicle with these modifications (0 - 60 mph in 3.68s), although quarter mile times suffer as power is reduced before the full quarter mile is finished, and therefore, also results in a lower trap speed (11.91s @ 110 mph).
Any suggestions, thoughts or guidance is appreciated; thank you.
What temps are you driving in? The car will cool better at high speeds which might explain why you don't have the issue at highway speeds. Maybe the increased boost pressure is putting a strain on the cooling system?
Last edited by Gungaslow; May 4, 2018 at 07:28 PM.
What temps are you driving in? The car will cool better at high speeds which might explain why you don't have the issue at highway speeds. Maybe the increased boost pressure is putting a strain on the cooling system?
Clearly this information would have been beneficial to know prior to spending ~$2,400 on a tune, but I'm glad they're aware of this issue and hopefully they remedy it shortly.
Clearly this information would have been beneficial to know prior to spending ~$2,400 on a tune, but I'm glad they're aware of this issue and hopefully they remedy it shortly.
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The dealership is aware that I had my ECU flashed by Eurocharged. All system updates were done prior to having the ECU flashed and the build date of this vehicle is February of 2017.
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The boost limiters just need to be simply adjusted. The barometric pressure sensor is reading high so it cuts the boost.
Does anyone have a v3 dyno sheet with boost and afr readings? It might tell you what's going on, v3 from any of the big 3 tuners.






