Mercedes-AMG M178 Turbo Upgrade Guide — Stage 3 & Stage 4 | AMG GT, GTS, GTR
The Mercedes-AMG M178 4.0-litre twin-turbo V8 is the dry-sump variant of AMG’s 4.0T engine family, engineered specifically for the AMG GT lineup — the GT, GT S, GT C, and GT R (C190/R190). With a flat-plane-inspired firing order, lower centre of gravity, and dedicated oil system designed for sustained lateral loads, the M178 is built for track work from the factory. Stock power ranges from 469 HP in the base GT to 577 HP in the GT R, but the engine’s forged crankshaft and robust bottom end support significantly more with the right turbo hardware.
This guide covers the complete turbo upgrade path for M178-equipped AMG GT models — from Stage 3 builds targeting 900 WHP to full Stage 4 packages pushing past 1,000 WHP.
Factory M178 Turbo Limitations
The factory turbochargers on the M178 share their basic architecture with the M177’s units but are calibrated for the GT platform’s higher-revving nature. They deliver strong mid-range response but run out of airflow capacity around 650–700 WHP. Beyond that point, compressor efficiency drops, exhaust gas temperatures rise sharply, and the turbos are operating well past their designed efficiency range.
The M178’s dry-sump oiling system and lower engine position in the GT chassis create unique packaging considerations. Turbo upgrades for the C190 must account for the GT’s distinctive front-mid engine layout, tighter transmission tunnel clearance, and specific oil feed routing that differs from the M177’s wet-sump applications.
Stage 3 Turbo Upgrade — 900 WHP
The Stage 3 turbo upgrade for the M178 replaces the factory turbochargers with larger-frame units that significantly extend the engine’s airflow capacity. On 98 RON pump fuel with supporting modifications, the M178 Stage 3 setup targets approximately 900 WHP — a substantial improvement over the factory turbos’ effective ceiling.
AMG GT C190 M178 Stage 3 Race Turbo Upgrade — this kit is purpose-built for the C190 platform and includes turbocharger assemblies validated for the dry-sump M178’s oil system, gaskets, oil lines, and all mounting hardware for a complete installation.
The Stage 3 kit maintains reasonably quick spool characteristics while delivering a dramatic increase in top-end power. For GT owners who track their cars regularly, this is the sweet spot — enough power to be genuinely fast without requiring a full engine teardown for forged internals.
Stage 4 Turbo Upgrade — 1,000+ WHP
For dedicated race builds and owners targeting maximum output, the Stage 4 turbo upgrade pushes the M178 into four-figure territory. The larger turbocharger frames flow enough air to support 1,000–1,200+ WHP when paired with forged internals, upgraded fuel delivery, and a comprehensive ECU calibration.
- M178 Stage 4 Turbo Upgrade — the full Stage 4 turbocharger kit specifically for the M178 dry-sump engine
- YPG M177/M178 Stage 4 Turbo Upgrade — the cross-platform Stage 4 kit compatible with both M177 and M178 applications
- Stage 4 Tuner Package (M177/M178) — a workshop-focused package for professional tuners building client cars
Stage 4 builds on the M178 demand the same level of supporting modifications as on the M177 — forged internals, upgraded fuel system, and ported cylinder heads are strongly recommended at this power level.
Stage 3 vs Stage 4 — Choosing the Right Build
| Stage 3 | Stage 4 | |
|---|---|---|
| Power Target | ~900 WHP | 1,000–1,200+ WHP |
| Spool | Quick spool, strong mid-range | Slightly later spool, dominant top-end |
| Internals | Factory internals viable with conservative tune | Forged internals required |
| Best For | Track-focused street car, spirited driving | Dedicated race builds, roll racing, maximum power |
Supporting Modifications for M178 Turbo Builds
Downpipes
Aftermarket downpipes are essential for reducing exhaust backpressure and allowing upgraded turbochargers to spool efficiently. The AMG GT’s factory catalytic converters are particularly restrictive and represent one of the largest single gains available.
AMG GT/GTS/GTR M178 Downpipes — available in catless, 200-cell, and 400-cell configurations to suit different requirements.
Blow-Off Valve
An upgraded blow-off valve manages the increased boost pressure from larger turbochargers and protects against compressor surge during aggressive driving.
Forged Internals
The M178’s factory internals are reliable on Stage 3 builds with conservative tuning, but Stage 4 power levels demand forged pistons and connecting rods to handle the significantly higher cylinder pressures.
M178 Forged Internals — complete forged piston and rod kit for the M178 dry-sump V8.
Ported Cylinder Heads
CNC-ported heads improve airflow capacity and support higher boost levels. On Stage 4 M178 builds, ported heads are a meaningful contributor to both peak power and mid-range torque delivery.
Crate Engines
For complete engine builds or high-mileage replacements, YPG Motorsport offers fully assembled M178 crate engines built to performance specifications with forged internals and ported heads.
Exhaust System Upgrades
Beyond downpipes, a full exhaust system upgrade removes additional backpressure from the mid-pipes and rear section. For AMG GT owners looking for a complete exhaust solution:
AMG GT/S/C Valved Exhaust with Mid-Pipes — a Capristo valved exhaust system with cat-delete mid-pipes and OEM cat adapters for the M178 platform.
ECU Tuning
Every turbo upgrade requires a matching ECU calibration to deliver its full potential. The tune adjusts boost targets, fuelling, ignition timing, and traction control parameters for the new turbocharger hardware. Browse AMG GT ECU tuning options.
Fuel Considerations — 98 RON in the GCC
Stage 3 M178 builds run reliably on 98 RON pump fuel — the standard high-octane grade available across the GCC. Stage 4 builds targeting 1,000+ WHP are achievable on 98 RON with conservative timing, though methanol injection or E85 blending provides additional headroom for maximum power extraction.
Watch: AMG GT M178 Builds
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Related Guides
Frequently Asked Questions
What is the difference between the M178 and M177?
The M178 is the dry-sump variant of AMG’s 4.0T V8, used exclusively in the AMG GT lineup (C190/R190). It features a lower engine mounting position, dry-sump oiling for sustained lateral loads, and a higher-revving calibration compared to the wet-sump M177 used in the C63, E63, GLC63, and GT63.
Can I use M177 turbo kits on an M178 engine?
Some turbo kits are cross-compatible — the YPG Stage 4 kit and the Tuner Package are validated for both M177 and M178. However, the Stage 3 kits are chassis-specific due to differences in oil feed routing and packaging between the AMG GT and other M177 chassis.
Do I need forged internals for the Stage 3 kit?
For Stage 3 builds targeting approximately 900 WHP, the factory M178 internals are typically adequate with a conservative tune. Forged internals are recommended for builds targeting sustained high-load use or as a precaution for owners who plan to advance to Stage 4 later.
What power can the M178 Stage 4 achieve on 98 RON?
On 98 RON pump fuel with forged internals, ported heads, and a calibrated tune, Stage 4 M178 builds typically produce 1,000–1,100 WHP. Methanol injection or E85 blending extends the ceiling beyond 1,200 WHP.
Is the AMG GT’s dry-sump oiling system a concern for turbo upgrades?
The dry-sump system is actually an advantage for performance builds — it maintains consistent oil pressure under high lateral loads and aggressive driving. YPG’s M178 turbo kits are designed to work with the dry-sump system’s specific oil feed and return routing.