Upgrading the intake manifold on a BMW 128i can significantly impact performance. This article documents the process of installing a 3-stage intake manifold (3SIM) and a Euro-spec airbox on a 128i, focusing on the challenges, costs, and potential gains. This upgrade, when paired with proper car tuning in Somersby (or your local area), can truly unlock your vehicle’s hidden power.
The 3-Stage Intake Manifold (3SIM) Installation Process
The installation of a used 3SIM sourced from a junkyard required approximately three hours, including meticulous cleaning, gasket replacement, and careful handling of hoses and sensors. Small hands proved advantageous, particularly for accessing tight spaces around the throttle body and wiring box bracket. While the process isn’t inherently difficult, attention to detail is crucial. A pre-emptive purchase of an extra PCV hose proved wise, as the existing one was intentionally broken for easier removal.
The junkyard 3SIM was thoroughly cleaned before installation:
New OEM DISA valves were purchased and compared to the old ones from the junkyard manifold:
A key component of this upgrade was swapping the USDM airbox for a Euro-spec version:
The Euro airbox, equipped with a new K&N conical filter, promises improved airflow:
The USDM airbox requires removal for filter changes:
Removing the OEM single-stage intake manifold revealed the similarities in size and shape to the 3SIM, with the primary difference being the DISA valves:
For easier access, the power steering reservoir was moved and the driver-side strut brace removed:
The completed installation, featuring the 3SIM and Euro airbox, maintains an OEM appearance:
Wiring and Tuning for the 3SIM
The wiring harness is compatible with both DISA and non-DISA setups, simplifying the connection process. However, to fully utilize the 3SIM’s potential, ECU tuning is necessary to activate the DISA valves. This is where professional car tuning in Somersby, or a reputable tuner in your locale, comes into play. Without a tune, the ECU won’t recognize the DISA valves, limiting performance gains. A Bimmworks tune was chosen for this project, requiring a 30A battery charger to ensure a stable ECU flashing process.
Cost Considerations and Performance Expectations
The total cost of this project, including junkyard parts, new OEM components, tuning software and the tune itself, reached approximately $1,387. This significant investment underscores the importance of considering the cost-benefit ratio. While the 3SIM offers performance advantages over the single-stage manifold, particularly below 6500 RPM, alternative options like a modified N54 intake manifold provide a cheaper, albeit higher-RPM focused, upgrade path. Dyno testing will ultimately determine the actual power gains achieved by the 3SIM and Euro airbox combination.
Suspension Upgrades for Enhanced Handling
In addition to the engine upgrades, a Bilstein B12 cup kit was installed to improve handling:
This cost-effective suspension upgrade aims to enhance handling without the expense of coilovers. A future review will assess the performance of the B12 kit. This, combined with the engine tuning, will contribute to a more engaging and responsive driving experience.
Conclusion
Upgrading to a 3SIM and Euro airbox, coupled with professional car tuning in Somersby or elsewhere, offers a potential pathway to increased performance for the BMW 128i. While not the most budget-friendly modification, the 3SIM provides a unique blend of mid-range power enhancement and OEM aesthetics. The ultimate value of this upgrade will be determined by dyno results and real-world driving experience.
