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Air and Fuel› Fuel Injection Systems and Components - Electronic

Nostrum

Stage 2 DI Injectors for BMW S55/N55 3.0L

$1,799.00 $1,750.00 Save $49.00

SKU: H703-1257

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INSTALL DIFFICULTY
DIY PRO SHOP

Moderate — 2–4 hours

Overview

The Nostrum Stage 2 DI Injectors are a high-performance fuel upgrade for BMW 3.0L S55 and N55 engines. These injectors are engineered to flow 55% more fuel than stock S55 units, supporting high-horsepower builds without the need for secondary port or methanol injection systems.
Show original supplier description
The Nostrum Stage 2 DI Injectors are a high-performance fuel system upgrade designed specifically for BMW 3.0L N55 and S55 engine platforms. By delivering a 55% increase in fuel flow over stock S55 injectors and 12% over EU5 M5 injectors, they provide the necessary capacity to support outputs exceeding 900 wheel horsepower on gasoline. The kit features a direct-fit design that integrates with the factory ECU diagnostics and safety functions, eliminating the requirement for complex secondary controllers or aftermarket meth injection setups. Each set of six injectors is production-tested with over 700 data points to ensure flow consistency within +/- 5%. The injectors are supplied with pre-installed decoupling rings and comprehensive installation instructions. For optimal performance and idle quality, professional coding using tools like BMW ISTA+ or Autel MaxiSys is recommended. Proper tuning is mandatory, with data support available for platforms including EcuTek, Bootmod3, and MHD. Nostrum has not validated these injectors for the S63 or N63 engine platforms, and they are not compatible with those systems. These injectors are sold in matched sets of six. Nostrum backs these components with a lifetime warranty, and calibration engineering support is available to assist with the setup and tuning process.
Vehicle Symptoms
  • fuel cut at high rpm under boost
  • lean air/fuel ratio at wide open throttle
  • misfire above 6000 rpm after turbo upgrade
  • maxed out injector duty cycle on stock fuel system
  • loss of top-end power on E85 or high boost
Diagnostic Codes
  • P0171 – FT Malf (B1)
  • P0174 – FT Malf (B2)
  • P0300 – random misfire
  • P0301 – Cylinder 1 misfire Det
  • P0302 – Cylinder 2 misfire Det
Relevant Conversations
  • N55 injector duty cycle 100% at 600whp
  • S55 injectors maxed out lean fuel trim P0171
  • Nostrum stage 2 DI injectors vs stock S55
  • BMW N55 900whp fuel system upgrade
  • P0300 random misfire after bigger turbo N55
  • Nostrum H703-1257 install time
  • S55 low pressure fuel pump upgrade for Nostrum injectors
  • N55 port injection vs Nostrum DI injectors
  • MHD fuel injector scaling Nostrum stage 2
  • S55 high pressure fuel pump stage 2 injectors

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

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Specifications

BrandNostrum
Part NumberH703-1257
CategoryAir and Fuel
5,000+ Trusted brands
1M+ Enthusiasts
5M+ Parts sold
(760) 282-4645 hello@motormia.co

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Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

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