Infiniti G37 Firing Order: VQ37VHR’s 1-2-3-4-5-6 Sequence

2. Why Does Firing Order Matter for Your G37? (Engine Balance & Performance)

The firing order directly affects engine smoothness, crankshaft torsional vibration, exhaust tuning, and even fuel distribution. Because the Infiniti G37’s VQ37VHR uses a 60-degree V-angle, the 1-2-3-4-5-6 firing order alternates between banks: Bank1 (cyl1) → Bank2 (cyl2) → Bank1 (cyl3) → Bank2 (cyl4) → Bank1 (cyl5) → Bank2 (cyl6). This prevents two cylinders on the same bank from firing consecutively, which reduces rocking couple and enhances longevity. The correct firing order ensures optimal scavenging in the dual exhaust, maximizes volumetric efficiency, and contributes to the 330+ hp output. A wrong order will cause violent misfires and potential engine destruction.

3. Types of Firing Orders: Even-Fire vs Odd-Fire (G37 context)

Most V6 engines fall into two categories: even-fire (equal 120° intervals) and odd-fire (uneven intervals, e.g., 90° and 150°). The Infiniti G37 uses the even-fire pattern with 1-2-3-4-5-6. Other common V6 firing orders include 1-4-2-5-3-6 (Honda J-series), 1-6-5-4-3-2 (GM 3800), and 1-4-5-2-3-6 (some Ford Duratec). However, the VQ family’s unique crankshaft phasing relies on 1-2-3-4-5-6. The advantage of even-fire is smooth idle, high-RPM stability, and reduced harmonic stress.

4. How To: Check & Diagnose Firing Order on G37 (Step-by-Step)

Because the G37 uses coil-on-plug ignition with no distributor, verifying the firing order is mostly about cylinder numbering and misfire detection. Follow these steps:

• Step 1 – Identify cylinder layout: Cylinder #1 is the frontmost cylinder on the passenger side (Bank 1). #2 is front driver side. #3 middle passenger, #4 middle driver, #5 rear passenger, #6 rear driver.
• Step 2 – Use OBD2 scanner: Look for misfire codes (P0301 = cyl1 misfire, P0302 cyl2, etc.). Random multiple misfire (P0300) suggests possible firing order confusion if wiring was tampered.
• Step 3 – Perform a power balance test: With a professional scan tool, command each injector or coil off. The RPM drop should be uniform across cylinders. Uneven drop may indicate a cross-fired ignition coil harness.
• Step 4 – Inspect ignition coil connectors: Ensure that each coil harness is connected to the correct cylinder. Misrouted wiring can cause wrong firing order despite ECU signals.
• Step 5 – Verify with oscilloscope (advanced): Check primary ignition waveform order against crankshaft position sensor signal.

5. Is It Safe to Change the Firing Order on an Infiniti G37?

Absolutely NOT safe. The VQ37VHR engine’s crankshaft counterweights, camshaft profiles, valve timing, and ECU ignition maps are all engineered specifically for the 1-2-3-4-5-6 firing sequence. Altering the firing order—for example by remapping the ECU to a different sequence or physically swapping coil wires—will cause immediate misfiring, backfires through the intake manifold, catastrophic piston-to-valve contact, bent connecting rods, and total engine failure. Even aftermarket standalone ECUs require a custom billet crankshaft to change order, which is not practical for G37 owners. Therefore, always maintain factory order.

6. Advantages of the Factory 1-2-3-4-5-6 Firing Order

• Exceptional smoothness: Alternating bank firing eliminates perceptible vibration, even at 7500 rpm redline.
• High power density: VQ37VHR produces 330–348 hp thanks to optimal combustion phasing and cylinder pressure distribution.
• Fuel efficiency: Even firing intervals improve mixture homogenization and reduce knock tendency.
• Longevity: Crankshaft main bearing wear is minimized due to balanced load intervals.
• Signature exhaust note: The 1-2-3-4-5-6 firing order creates the iconic VQ growl, especially with aftermarket catbacks.
• Simpler diagnostics: Misfire detection is straightforward because the firing pattern is sequential and predictable.

7. Disadvantages & Consequences of Wrong Firing Order

• Severe engine shaking: Unbalanced power strokes cause the entire drivetrain to shudder.
• Catastrophic internal damage: Pistons may hit open valves if ignition timing is misaligned with order.
• Check engine light with multiple codes: P0300–P0306, plus catalyst damage codes (P0420/P0430).
• Loss of up to 70% power: The engine will struggle to idle and may stall.
• Overheating catalytic converters: Unburnt fuel ignites in the exhaust, melting substrate.
• Reduced fuel economy: Can drop below 8 mpg.

8. Practical Use of Firing Order Knowledge (Maintenance & Tuning)

Understanding the 1-2-3-4-5-6 sequence helps in several real-world scenarios: replacing spark plugs (correct cylinder order not critical but knowing which coil belongs to which cylinder helps), compression testing – you can test in firing order to spot issues, injector flow testing, and aftermarket ECU tuning (to ensure ignition timing per cylinder matches sequence). Also, when installing a performance ignition system or standalone, the firing order must be configured correctly in the software. For DIY owners, it aids in understanding why a single misfire affects the entire firing sequence.

📋 VQ37VHR Firing Order & Engine Data Sheet