M177 / M178 Equal-Length Turbo Exhaust Manifold — Patent-Pending, 3D-Printed

Made to order — 4 week lead time. Cerakote option adds 1–2 weeks.

The first equal-length exhaust manifold for the M177/M178 4.0L twin-turbo V8 — patent-pending, CFD-developed, and metal 3D-printed so the geometry that scavenges the hot-V is the geometry you bolt on. 100% made in America.

Physics first. Then the right way to build it.

Most aftermarket manifolds start with a question: what can we make cheaply? We started with a different one: what runner geometry actually scavenges an M177 hot-V? We designed exactly that — equal-length runners so every cylinder's blowdown pulse reaches the turbine on even spacing, shallow approach angles into a CFD-shaped collector, and a 46 mm turbo entry sized to the turbine's real limit — validated it in CFD, and then chose the manufacturing process that reproduces it faithfully.

For this part, that's metal 3D printing — laser powder bed fusion in 316L stainless. Not because it's novel, but because it's the best way to build tight-radius runner crossings, continuous wall paths, and CFD-exact internal surfaces as a single seamless structure. No weld seams in the hottest, highest-stress zone on the engine. No draft angles or parting lines compromising the flow path. The part you bolt on is the part we modeled. Read the full engineering write-up →

Why the geometry matters

Anyone can make a runner bigger. But raw volume alone slows exhaust gas velocity and lets pulses collide and reverse back into the port — trapping burnt gas and killing spool. Our tuned runner paths and organically merged collector keep each cylinder's pulse separated and moving, so one cylinder's blowdown helps draw the residual charge out of the next. Cleaner evacuation, more fresh air per stroke, a harder-driven turbine. That geometry is patent-pending.

Proven on the dyno — not just on paper

Back-to-back, same car, same tune, manifold change only: +66 whp at 5,200 rpm, +52 whp average from 4,500–5,600 rpm, and +60 lb-ft of peak wheel torque — the range these cars actually live in. It matches the stock manifold's peak torque 500 rpm sooner, then keeps climbing another 60 lb-ft to a level the stock part never reaches. Full boost arrives 400–800 rpm sooner, and the curve never drops below stock anywhere in the sweep. This is what real scavenging looks like: a broad, usable powerband, not a narrow top-end spike.

Built to outlast

Heat-treated 316L stainless, 3D-printed as a single optimized structure with CNC-machined sealing faces and V-band turbo flanges — no weld seams to crack under thermal cycling. Optional Cerakote thermal barrier.

Features

• First equal-length exhaust manifold for the M177 — even pulse spacing, equal backpressure every cylinder
• Patent-pending inboard-exhaust scavenging design — exclusive to ModalWorks
• Metal 3D-printed (LPBF) — chosen because it reproduces the CFD-optimized geometry exactly, seam-free
• Dyno-documented: +66 whp @ 5,200 rpm, +52 whp avg 4,500–5,600, +60 lb-ft peak torque, manifold alone
• Reaches stock's peak torque 500 rpm sooner; stock never reaches 850 lb-ft, ours does at ~4,950 rpm
• Full boost 400–800 rpm sooner; no losses at any rpm
• CFD-developed runners and collector — 46 mm turbo entry (stock 42 mm, +20% area)
• Heat-treated 316L stainless, CNC-machined sealing surfaces
• Optional Cerakote thermal-barrier finish
• 100% made in America

Vehicle Applications

• 2015–2021 Mercedes C63 AMG, Base (W205)
• 2015–2021 Mercedes C63 AMG, Coupe (C205)
• 2015–2021 Mercedes C63 AMG S, Base (W205)
• 2015–2021 Mercedes C63 AMG S, Coupe (C205)
• 2015–2021 Mercedes AMG GT (C190)
• 2015–2021 Mercedes AMG GT S (R190)
• 2017–2021 Mercedes AMG GT C (C190)
• 2017–2021 Mercedes AMG GT R (R190)
• 2017–2021 Mercedes GLC63 AMG (X253)
• 2017–2021 Mercedes GLC63 AMG S (X253)
• 2017–2021 Mercedes GLC63 AMG, Coupe (C253)
• 2017–2021 Mercedes GLC63 AMG S, Coupe (C253)

Running M177.2 turbos? An M177.2-specific version is in development and coming soon — contact us to be notified.

Notes

Direct bolt-on to OEM flanges and the factory turbo interface. Due to the increased runner size, the OEM decorative heat shield requires a simple trim to clear. The Cerakote option provides thermal insulation on the exhaust if you prefer to run without the shield.

Images show raw (uncoated) 316L units as printed.