M177 vs M178 AMG Engine Comparison
M177 vs M178 — AMG 4.0T V8 Engine Comparison
Mercedes-AMG’s 4.0-liter twin-turbo V8 comes in two variants: the M177 and the M178. They share the same basic architecture — 4.0L displacement, twin-scroll turbochargers in a hot-V configuration, and hand-built "one man, one engine" assembly — but differ in critical ways that affect performance, tuning potential, and application. Understanding the differences is essential when choosing parts, calibrations, and build paths.
Technical Comparison
| Specification | M177 | M178 |
|---|---|---|
| Displacement | 3,982 cc | 3,982 cc |
| Crankshaft | Cross-plane (90° firing order) | Flat-plane (180° firing order) |
| Oiling System | Wet sump | Dry sump |
| Factory HP Range | 469–630 HP | 476–730 HP |
| Rev Limit | ~6,500–7,200 RPM | ~7,200–7,600 RPM |
| Character | Deep V8 rumble, massive low-end torque | Higher-pitched, sharper, more rev-happy |
| Mounting | Front-longitudinal in standard chassis | Front-mid, lower center of gravity |
| Applications | C63, E63, GT63, GLC63, G63, GLE63 | AMG GT, GT R, GT S, GT C, GT Black Series |
Flat-Plane vs Cross-Plane Crank
The most significant difference between the M177 and M178 is the crankshaft. The M177 uses a conventional cross-plane crank that produces the classic V8 burble and delivers massive torque from low RPM. The M178’s flat-plane crank fires the cylinders in an even left-right-left-right sequence, creating a sharper, higher-pitched exhaust note and enabling the engine to rev higher and breathe more efficiently at the top of the RPM range.
The flat-plane design also reduces rotational inertia, allowing faster throttle response and quicker spool — but it introduces more secondary vibration, which is why Mercedes pairs the M178 with a dry-sump oiling system and reinforced engine mounts in the dedicated AMG GT sports car platform.
Tuning Differences
Both engines respond exceptionally well to ECU tuning, but the calibration approach differs:
- ▸ M177: Huge torque gains in the midrange. Stage 1 tunes unlock 80–100 HP. The cross-plane crank loves boost. With forged internals and turbo upgrades, 800+ WHP builds are proven — including our 828 WHP world record C63.
- ▸ M178: More top-end focused gains. The flat-plane crank rewards high-RPM calibrations. Stage 1 tunes unlock 60–80 HP. Stage 2+ with downpipes opens up significantly more. The dry-sump system handles sustained high-g loads better for track use.
Which Engine is Better for Tuning?
The M177 offers more accessible, higher-magnitude gains — especially at Stage 2 and Stage 3 where the cross-plane crank’s torque characteristics pair perfectly with bigger turbos. It’s also more widely available, with parts and calibrations well-established across multiple chassis.
The M178 shines on track where the flat-plane crank’s higher rev ceiling and the dry-sump oiling system provide advantages under sustained lateral and longitudinal g-forces. For pure drag racing, the M177 is typically preferred; for circuit racing, the M178 has inherent advantages.
YPG Motorsport offers full ECU tuning, crate engines, and performance parts for both the M177 and M178 platforms.