Turn up the boost on an N54 or N55 and the factory plugs are usually the first thing to complain. You feel it as a stumble at the top of third gear or a misfire code the morning after a hard pull. The fix starts with getting heat out of the combustion chamber faster.
The Dinan Iridium Spark Plug with HV terminal fits the BMW N20, N54, N55, S55, N63 and S63 engines. At heat range 9 it runs one step colder than OEM on the N20, S55, N63 and S63, two steps colder on the N55, and three steps colder on the N54. Each engine gets the jump it needs to stay stable under added boost.
A Colder Iridium Spark Plug for Tuned N54, N55 and S55 Engines
The center electrode is tipped with iridium over a copper core. Iridium has a 152% higher melting point than silver, 125% higher than copper and 38% higher than platinum, so the tip keeps its shape under high cylinder pressure. The copper core pulls heat away from the tip, and the colder heat range carries it out of the chamber quickly to resist pre-ignition.
Running a stock N54 or N55? Read this first. Dinan suggests this plug on those two engines for tuned, high-boost or upgraded-turbo cars only. On a non-tuned N54 or N55 it runs too cold and can foul and misfire. On the N20, S55, N63 and S63 it is one step colder than OEM.
Iridium Spark Plug Specs and Legal Status
Each plug ships pre-gapped at 0.5mm with a flat seat, 14mm Bi-Hex and a non-removable nut (HV) terminal, so it drops into the factory location. Before you order, know this: it is not legal for sale or use in the State of California. Sold individually, so order one per cylinder. Dinan part number D640-0002. Sold by AutoTecknic, an authorized Dinan dealer.
What's Included
- One Dinan iridium spark plug, 12x26.5x14mm, HV terminal, heat range 9
Key Features
- Heat range 9: 1 step colder than OEM on N20, S55, N63 and S63
- 2 steps colder than OEM on N55, 3 steps colder on N54
- Iridium center electrode tip with copper core
- Iridium: 152% higher melting point than silver, 125% higher than copper, 38% higher than platinum
- 12mm thread, 26.5mm reach, 14mm Bi-Hex, flat seat, non-removable nut (HV) terminal
- Supplied gap 0.5mm, install torque 17 Nm
- Replaces OEM 12120039664, 12120038896 and 12120038704
Vehicle Fitment
Dinan lists this spark plug by engine family:
- BMW N20
- BMW N54 (tuned, high-boost or upgraded-turbo applications only)
- BMW N55 (tuned, high-boost or upgraded-turbo applications only)
- BMW S55
- BMW N63 and N63TU
- BMW S63 and S63TU
Not suggested for non-tuned, stock N54 or N55 engines.
Installation Notes
Plug swaps are a basic DIY job with a spark plug socket, extension and torque wrench, though the V8 N63 and S63 take more time to reach. The plugs come pre-gapped at 0.5mm, so check the gap but do not open it up. Work on a cold engine.
- Let the engine cool completely and remove the engine cover.
- Unplug and pull each ignition coil.
- Blow debris out of each plug well, then remove the old plugs.
- Thread each Dinan plug in by hand to avoid cross-threading.
- Torque to 17 Nm, then reinstall the coils and engine cover.
