Spool BMW B58 Gen 2 Auxiliary Split Fuel System
Spool BMW B58 Gen 2 Auxiliary Split Fuel System
Spool BMW B58 Gen 2 Auxiliary Split Fuel System separates the direct-injection and port-injection fuel feeds for more stable, boost-referenced fueling on higher-output BMW B58 builds.
- Dual Walbro 450 pumps supplied as the base configuration
- Optional dual Walbro 525 configuration for higher fuel demand
- OEM fuel-pump top-hat integration using precision-machined fittings
- Plug-and-play ReFlex controller compatibility
- Triple-layer PTFE fuel plumbing with stainless reinforcement
- Compact boost-referenced Spool fuel-pressure regulator
Fitment: BMW B58 Gen 2 applications listed by Spool: M340i/M340i xDrive 2020+, M440i/M440i xDrive 2021+, X3 M40i 2020+ and X4 M40i 2020+.
Important: Spool's solid-state PWM relay harness is a separate option. Confirm pump choice, port-injection controller, injector size and base pressure with the tuner.
Dispatch: Special order — allow 3–4 weeks.
Confirmed catalogue fitment
- Engine families: B58
- BMW chassis: G20, G21, G22, G23, G26, G01, G02
- Vehicle models: M340i, M440i, X3 M40i, X4 M40i
Fuel-system selection and installation
Fuel-system parts must be selected around the complete combination of engine generation, fuel type, target output, existing pump and injector configuration, and the calibration strategy. A component appearing for an engine family does not mean it replaces every factory or upgraded fuel-system arrangement used on that engine.
Professional installation and calibration are recommended where the product changes fuel pressure, pump control, injector flow, ethanol-content input or port-injection operation. Confirm wiring, plumbing, electrical load, controller requirements and compatible supporting hardware before ordering.
Before ordering
Select your exact BMW through MLAB My Garage and review the product options, included parts and installation requirements. Where a vehicle has been modified from its original engine, transmission or fuel-system specification, contact MLAB with the VIN and current hardware list so the combination can be checked before supply.
MLAB support
MLAB by Boost and Tune can assist with product selection, workshop installation and dyno calibration for supported BMW applications in Melbourne. Product availability and lead time should be confirmed when ordering supplier-built or special-order components.
Supplier specification & ordering notes
- Separate direct-injection and port-injection feeds reduce interaction between their pressure demands. The port-injection side uses boost-referenced regulation.
- The system retains the factory pump top hat with machined fittings and supplies a Reflex-compatible harness. A billet top hat is optional.
- Dual Walbro 450 pumps are the standard supplier configuration, with 525 upgrades available. Confirm the selected MLAB variant.
- The optional full-PWM arrangement needs two separately supplied PWM harnesses per auxiliary fuel-system kit.
- The included hoses use a PTFE core, stainless reinforcement and a nylon outer layer. A compact Spool regulator is included.
Chassis: G20, G21, G22, G23, G26, G01, G02
Engines: B58
View compatible BMW ranges
M340i, M440i, X3 M40i, X4 M40i
View full year and variant fitment
PROFESSIONAL FITTING AVAILABLE
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Have this part professionally fitted, checked and configured by our BMW performance workshop.
Product: Spool BMW B58 Gen 2 Auxiliary Split Fuel System
Workshop installation in Albion, Victoria
Vehicle compatibility
Fits these BMW platforms
Select a BMW in My Garage to check this product.
Use the BMW vehicle selector and confirm VIN, model year, drivetrain, steering side and factory options before ordering.
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