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Dyno Test Results
4 min read
The quick answer: A completely stock 2020 Mercedes-AMG GT C made 556 WHP and 567 WTQ on our Mustang Dynamometer. Two pulls, two nearly identical results. This is the baseline every C190 GT C build starts from, and it sets the stage for what comes next.
Before we start bolting things on, we put the car on the dyno stock. No tune, no hardware changes, nothing touched. We wanted clean numbers from this specific car at this specific point in time, because every future test on this platform starts here. This is what a 2020 AMG GT C makes at the wheels on a Mustang Dynamometer.
Test Setup
The test vehicle is a 2020 Mercedes-AMG GT C, running the M178 4.0L twin-turbo V8 in completely stock configuration. No prior modifications, no aftermarket tuning, factory exhaust, factory intake, factory everything. Two pulls on a Mustang Dynamometer on 93 octane pump gas.
Test vehicle: 2020 Mercedes-AMG GT C (C190)
Engine: M178 4.0L V8 Biturbo
Configuration: 100% stock, no modifications
Dyno: Mustang Dynamometer
Fuel: 93 Octane Pump Gas
Total runs: 2
The Numbers
Two pulls, 3 WHP and 3 WTQ separating them. That level of consistency across back-to-back runs tells you two things: the car was fully at temperature and stable when we started, and the M178 is producing its power reliably and repeatably on the stock setup. These are not cherrypicked numbers from one exceptional pull. This is what the car does.
Full Data
| Run | Configuration | WHP | WTQ (lb-ft) |
|---|---|---|---|
| 1 | Stock | 559 | 564 |
| 2 | Stock (Best) | 556 | 567 |
We are reporting the best run as Run 2 based on peak torque, which is the more meaningful figure at the stock power level on this engine. Peak WHP was marginally higher on Run 1 at 559 vs 556, but the 3 WHP difference is within normal dyno variance and the torque advantage on Run 2 at 567 vs 564 lb-ft reflects the fuller pull. Either number is the right answer. The car is producing in the 556 to 559 WHP and 564 to 567 WTQ range, stock, on pump gas.
Curve Analysis
The torque curve on the GT C tells the real story of the M178 in this application. Torque builds aggressively from 2,800 RPM and reaches its first peak near 3,500 RPM at approximately 548 lb-ft, before settling into a plateau through the mid-range. That plateau holds strong through 5,000 RPM, which is the characteristic shape of a well-sorted twin-turbo V8 that has been calibrated for broad, usable torque delivery rather than a single peak number.
Power climbs steadily behind the torque curve and hits its peak in the 5,400 to 5,600 RPM window at 556 WHP before beginning to roll off toward the 7,000 RPM redline. Both runs track each other extremely closely across the entire pull, confirming the consistency of the result.
One thing worth noting on the stock GT C: Mercedes-AMG rates this car at 550 hp at the crank. Our wheel numbers of 556 to 559 WHP represent the power measured at the wheels after drivetrain losses, which are typically in the 15 to 20 percent range on a rear-wheel drive car of this type. The wheel numbers suggest the GT C is producing meaningfully more than its rated crank output at the factory level, which is consistent with what tuners and dyno operators see across the M178 platform generally. AMG is conservative with their factory ratings.
What This Means
These stock numbers matter because of what comes after them. The GT C starts from a strong position in the C190 lineup. It carries the GT R's larger turbocharger specification from the factory, which means it has more hardware headroom than the base GT or GT S before any turbo upgrades are needed. The 550 hp factory rating is calibration-limited relative to the hardware, not hardware-limited relative to the engine's actual potential.
The upgrade path from these stock numbers follows a clear sequence. Downpipes address the exhaust restriction directly at the turbocharger outlets, which is the first real constraint on the M178 under sustained load. A heat exchanger upgrade addresses the charge-air cooling system's shared circuit with the transmission, which is the factory limitation that causes power to fall off on back-to-back pulls. An intake feeds the turbocharger inlets with higher airflow volume at lower temperatures. Charge pipes seal the system at elevated boost. And a supporting ECU calibration ties every hardware upgrade together and targets the boost levels the factory tune never reached.
Every future dyno session on this car will reference these stock numbers. This is the baseline. The gap between here and where this platform is going is exactly the story we are building.
FAQ
On our Mustang Dynamometer on 93 octane pump gas, our 2020 AMG GT C produced 556 to 559 WHP and 564 to 567 WTQ across two consistent pulls. Best run was 556 WHP and 567 WTQ.
Mercedes-AMG rates the GT C at 550 hp at the crank. Wheel horsepower is measured after drivetrain losses, which on a rear-wheel drive transaxle platform like the C190 typically run 15 to 20 percent. Our wheel numbers indicate the M178 in the GT C is producing more than 550 hp at the crank in real-world conditions, which is consistent with the broader M178 platform tendency to outperform its factory ratings on the dyno.
Yes. The GT C carries the GT R's larger turbocharger specification from the factory, which gives it more hardware headroom than the base GT or GT S starting point. The factory output is calibration-limited relative to the hardware the car already has, which makes it a particularly efficient platform to build with bolt-on upgrades and a supporting ECU tune.
In order: downpipes to address the exhaust restriction at the turbocharger outlets, a heat exchanger upgrade to solve the factory charge-air cooling limitation, an intake to improve turbocharger inlet flow, charge pipes to seal the system at elevated boost, and an ECU calibration to target the boost levels the factory tune was not using.
This is the starting line. Downpipes, intakes, heat exchangers, and charge pipes for the C190 AMG GT platform are in development at ARM Motorsports. Every future dyno test on this car will build from these numbers.
VIEW ALL C190 AMG GT UPGRADESThe ARM Team
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