RK Autowerks S58 Race Manifold — Billet Port Injection
What this actually does
Port injection is not a horsepower part. Anyone selling it that way is selling you a number. What it does is give the S58 a second, low-pressure fuel path so the engine is no longer limited by what the factory high-pressure pump can deliver — and that changes what a tuner is allowed to do with your calibration.
On a DI-only car, power gets pulled back at high ethanol content to stay inside the mechanical limits of the factory fuel system. That's why max-effort DI tunes end up leaner than anyone would like, and why they lean on exhaust cam timing workarounds to get there. Add port fuel and those constraints come off: full E85 instead of a carefully managed blend, richer air/fuel at load, lower cylinder and piston temperatures, and no band-aids in the tune.
The direct dyno gain from switching to full E85 on port injection is typically 10–30 WHP on the same tune. The real return is that the power you already make gets safer, and the power above it becomes available at all.
Do you need it yet?
Probably not, if you're on stock or bolt-on turbos running pump gas or a light ethanol blend. DI-only S58s have made 800+ WHP with high-flow injectors and a stronger low-pressure pump, so we're not going to tell you there's a wall at 600.
Where it earns its money: builds targeting sustained high boost on full E85, cars that keep pulling timing on max-effort DI calibrations, and anything being built to live at power rather than to survive one dyno pull. If you're not sure which side of that line you're on, call us and we'll tell you honestly — including if the answer is not yet.
Why the billet manifold instead of a rail kit
Port injection can be added to the factory manifold for a fraction of this price, and for a lot of builds that's the correct answer. This is the other end of the scale.
The factory S58 manifold is plastic. Under sustained boost that's a known weak point, and a split manifold takes the car off the road. This one is CNC-machined from solid 6061 with the fuel rail integrated into the casting rather than clamped to it — rigid, dimensionally stable, and one less thing to revisit at higher power.
It also consolidates hardware you'd otherwise be paying a fabricator for: six 1/8" NPT ports for methanol or nitrous, three more for sensors and boost reference. No bungs, no adapters, no welding.
Specifications
- CNC-machined 6061 billet aluminum
- Integrated -8AN ORB fuel rail, included
- Accepts Bosch EV14K (shorty) injectors
- 6 × 1/8" NPT ports — methanol or nitrous
- 3 × 1/8" NPT ports — sensors, boost reference
- Retains OEM oil filter access and factory service points
- Bolts to OEM mounting locations, factory gasket and hardware
- Available in Unfinished Aluminum or Thermal Black
- 31.6 lbs · 24 × 14 × 14 in
Fitment
BMW M2 G87 (2021+) · M3 G80 (2020+) · M4 G82 / G83 (2020+) · X3M / X4M F97 / F98 (2019+)
What else the build needs
Injectors and the port injection line kit are separate purchases. Sizing depends on fuel, target power, and whether port is supplementing DI or replacing it — and the shorty body requirement rules out a lot of common part numbers, so confirm before you buy six of the wrong thing.
Fuel supply matters too. The stock low-pressure pump is generally considered good to around 700 WHP once port injection is in play; past that, or on straight E85, plan for a pump upgrade and flex fuel hardware rather than finding out on a pull.
And it needs a tune. Dual-fuel control is not a bolt-on. We do this in-house as an authorized bootmod3 tuner, locally or remote.
Warranty
Covered under RK Autowerks' manufacturer warranty. Esse Werks is an authorized dealer — warranty claims are handled directly through us, not a support ticket in another state.
Notes
Off-road and competition use only. Requires tuning.
Shipping
Unfinished Aluminum in stock, ships from Boca Raton, FL. Thermal Black available to order.