The Infiniti G37, with its naturally aspirated 3.7-liter VQ37VHR V6 engine, has earned a reputation as a tuner-friendly platform that blends luxury with genuine performance potential. While the G37 outputs 330 horsepower from the factory (on later models), experienced owners know that 50+ horsepower gains are achievable with carefully selected upgrades that respect the vehicle's original engineering philosophy. This guide focuses on OEM+ modifications—upgrades that offer substantial power increases without sacrificing daily-driver reliability or requiring full engine teardowns. The VQ37VHR responds particularly well to improved airflow and optimized tuning, making it possible to reach 380–400 crank horsepower with a combination of bolt-on parts and a professional ECU recalibration.

The OEM+ Philosophy: More Power Without Compromise

OEM+ (Original Equipment Manufacturer Plus) means choosing parts that complement the factory design rather than forcing the engine into uncharted territory. Unlike radical builds that require forged internals, standalone ECUs, or constant maintenance, OEM+ mods exploit the headroom already built into the VQ37VHR. Key benefits include seamless integration with factory sensors and control systems; retained cold-start and idle quality; and a driving experience that feels refined, not raw. For the G37, this approach typically yields 50–80 wheel horsepower when combining intake, exhaust, headers, and a proper tune.

Many owners worry about triggering dashboard warning lights or compromising emission compliance. OEM+ parts are engineered to work within the engine's operating envelope, often featuring CARB EO numbers where applicable. The result is a car that accelerates harder, sounds more purposeful, and remains a pleasure to commute in. Every modification discussed here can be reversed if needed, preserving the car's resale value and long-term viability.

Planning Your Power Build

Before buying parts, understand that power mods are additive. A high-flow intake without a tune might only gain 5–8 hp, while pairing it with a cat-back exhaust and a retune can yield 15–20 hp from the combination. The biggest single gain comes from an ECU recalibration—typically 20–30 hp on an otherwise stock G37. Here is a logical upgrade path for reaching 50+ hp:

  1. ECU tune – foundation that unlocks the largest gains
  2. Cold air intake and cat-back exhaust – improve breathing
  3. Performance headers and high-flow catalytic converters – free up exhaust path
  4. Upgraded throttle body and intake manifold spacers – increase airflow volume
  5. Lightweight flywheel – sharpen drivetrain response

Each step builds on the previous, and the tune must be updated after each significant hardware change to maximize gains. It is also wise to address the G37's known weak points—the gallery gaskets and the transmission cooler—but those are reliability mods, not power mods. This guide focuses strictly on horsepower gains through OEM+ parts.

Top OEM+ Mods for 50+ HP

1. ECU Tuning (The 30-HP Gate Opener)

The VQ37VHR responds exceptionally well to reflashing its stock ECU. Factory fuel maps are conservative, and ignition timing is retarded for safety across different fuel qualities. A quality tune adjusts air-fuel ratios, advances timing, and raises the rev limiter to 7,500–7,600 rpm. On a completely stock G37, an ECU tune alone can unlock 20–30 horsepower at the wheels. Two dominant platforms are available:

  • UpRev Osiris – Widely used in the G37 community, allows user adjustment or professional remote tuning. Includes features like launch control and flat-foot shifting. Many shops offer pre-built maps for common mod combinations. UpRev official site
  • ECUtek – Used by many professional shops, offers race ROM options, lambda control, and advanced diagnostics. Preferred for those running E85 or custom setups. ECUtek official site

For most owners, a remote tune from a G37 specialist (like Z1 Motorsports or AdminTuning) is the most cost-effective path. Expect to pay $500–$800 for a complete setup including the cable and license. The tune also allows the car to adapt to other bolt-on mods, making it the single most important upgrade you can make.

2. High-Flow Intake Systems

The factory airbox is restrictive due to its silencing chambers and small inlet. Replacing it with a cold air intake that pulls air from inside the fender or behind the bumper, while upgrading to a larger, oiled or dry filter, can reduce intake restriction by 30–40%. Combined with a tune, expect 8–12 hp. Popular OEM+ choices include:

  • Stillen Gen 3 Cold Air Intake – The most popular option; CARB approved (EO D-660-3). Uses a large K&N filter and a heat shield to keep intake temperatures low. Stillen official site
  • Z1 High-Flow Intake System – Uses a large conical filter with heat shield, designed for stock or supercharged setups. Comes with a MAF housing adapter for a clean install. Z1 Motorsports
  • Injen SP Series – Features a long-tube design for cooler air and a polished intake tube. Injen Technology

Installation is straightforward, but the MAF sensor must be recalibrated via tune. Avoid heavily oiled filters if you live in dusty environments; some prefer dry filters (like AEM dryflow) for zero oil contamination risk. A proper intake also sharpens the VQ's induction sound, making it more aggressive without being obnoxious.

3. Cat-Back Exhaust System

The cat-back section (from catalytic converter to the rear tips) is where G37 owners first change the sound and free up flow. A 2.5-inch or 3-inch system reduces back pressure, especially at higher RPM where stock mufflers create significant restriction. On a tuned car with intake, a cat-back can add 5–8 hp. Two benchmark systems stand out:

  • Fast Intentions Cat-Back Exhaust – Handcrafted in the USA, uses a Helmholtz resonator to eliminate drone without packing. Available in 12” or 18” resonator lengths; the 12” is louder, the 18” is more civil. Fast Intentions
  • ARK Performance GRiP – T304 stainless, lightweight, produces a deep tone that matures nicely. Features a dual-wall tip design that resists bluing. ARK Performance

For OEM+ integration, stay with a cat-back that retains the factory second catalytic converters if you need to pass emissions. If you are able to run high-flow cats, adding an aftermarket Y-pipe (like Stillen or Z1) will net another 2–3 hp by smoothing the exhaust merge.

4. Performance Headers & High-Flow Cats

This is where real gains happen—often 15–20 hp on a tuned G37, but it requires removal of the factory exhaust manifolds. OEM+ headers should be shorty or mid-length to fit without modifying the steering shaft or oil pan. Reputable choices include:

  • Motordyne ART (Anti-Reversion Technology) Headers – 2.5-inch primaries, designed to scavenge without losing low-end torque. The ART design reduces reversion pulses, maintaining velocity at low RPM while flowing fully at high RPM. Motordyne
  • Z1 Shorty Headers – Direct fit, no cutting required, includes emissions-compliant high-flow cats. Designed to work with stock heat shields. Z1 Motorsports

Pair headers with a proper test pipe or high-flow cat section to maximize flow. Note: removing all catalytic converters will trigger a check engine light unless you use a tune with rear O2 sensor defeat. Many owners run Fast Intentions HFCs or Stillen HFCs for a good balance of flow and legality. With headers and high-flow cats, the G37's exhaust note becomes deeper and more aggressive, especially at wide-open throttle.

5. Upgraded Throttle Body

The VQ37VHR uses a drive-by-wire throttle body of 70mm diameter. Swapping to a bored unit (75mm or 80mm) can improve throttle response by 10–15%, though peak gains are modest (2–5 hp). It is best combined with a tune to utilize the extra opening. Options include:

  • JWT 70mm Throttle Body – Direct OEM replacement with larger bore, CNC-machined from billet aluminum. Jim Wolf Technology
  • Stillen 70mm Throttle Body – Same concept, comes with new gaskets and is pre-calibrated for the VQ37VHR.

Larger bore throttle bodies sometimes cause minor idle tuning issues, but a professional tune can resolve this. The benefit is more noticeable with headers and intake because the engine can actually use the increased airflow. Install takes about an hour and requires only basic hand tools.

6. Lightweight Flywheel

Reducing drivetrain inertia lets the engine rev quicker, especially in lower gears. A lightweight flywheel (10–13 lbs vs. stock ~22 lbs) can make the G37 feel 20–30 hp faster in gear changes and acceleration. It does not add peak power but enhances real-world responsiveness dramatically. Best for manual transmission cars. Recommended options:

  • Exedy Lightweight Flywheel – Chromoly steel, 10.9 lbs, comes with new pilot bearing. Exedy
  • ACT Prolite Flywheel – Aluminum, 9.5 lbs, reduces rotational mass significantly. Requires a clutch disc replacement as well. ACT Clutch

Installation requires transmission removal, so many owners pair it with a stronger clutch (like the South Bend Stage 2 daily or the ACT heavy-duty kit). The result is quicker rev-matching and a more immediate throttle response that transforms the driving experience.

7. Upgraded Fuel System (E85 Support)

If you plan to exceed 400 wheel horsepower, the stock fuel pump and injectors become limiting. However, for the 50+ hp target using pump gas, stock injectors suffice. If you add headers, full exhaust, and tune, you may consider DeatschWerks 600cc drop-in injectors or a Stock+ fuel pump if running E85. E85 can yield an extra 10–15 hp due to higher octane and cooling effect on the VQ engine. But for strict OEM+ gasoline builds, this step is optional until higher power goals. If you do decide to run E85, ensure your tuner supports flex-fuel or full E85 mapping, and be prepared for a 30% reduction in fuel economy.

Supporting Modifications for Reliability

With 50+ hp, the G37’s cooling system and drivetrain see increased stress. While not power-adding, these supporting mods ensure your gains last and prevent expensive failures:

  • Oil cooler (Setrab or Mishimoto) – Helps maintain consistent oil temps during hard driving. The VQ37VHR runs high oil temps from the factory, and adding power exacerbates this.
  • Transmission cooler (for automatic) – The 7-speed can overheat with repeated pulls; a cooler extends transmission life and helps maintain consistent shift quality.
  • Differential bushing insert – Reduces wheel hop when launching; cheap and easy to install.
  • Engine mounts (solid or polyurethane) – Reduce engine movement to protect headers and exhaust components from premature cracking.

Many G37 owners report that a properly tuned car with the above mods is reliable for 100k+ miles with routine maintenance. Also pay attention to spark plugs: upgrade to NGK LFR7AIX (one step colder) if you advance timing significantly.

Tuning & Customization: Getting the Most Out of Your Build

We cannot stress enough that an ECU tune ties every modification together. Without it, you are leaving 15–20 hp on the table. When ordering a tune, provide the tuner with a complete list of modifications, fuel type (91, 93, or E85), and your driving preferences (street vs track). Many tuners offer remote tuning sessions where you datalog and send files back and forth. For the G37, the most recommended tuners include:

  • AdminTuning (Sam) – Specializes in VQ engines, known for smooth street tunes that maintain drivability.
  • Z1 Motorsports – Offers both mail-order tunes and dyno sessions at their Alabama facility. Their database covers thousands of G37 builds. Z1 Tuning
  • RS Enthalpy – Experienced with UpRev and ECUtek, also offers transmission tuning for automatic cars.

A final consideration: the G37’s transmission calibration. For automatic cars, ask your tuner to adjust shift firmness and shift point to match the new power curve. Some tuners offer transmission control unit (TCU) tuning via UpRev or dedicated transmission software. This prevents premature clutch wear and improves shift feel under heavy acceleration.

Putting It All Together: Real-World Gains

To illustrate the potential of an OEM+ build, here is a typical combination and the estimated wheel horsepower gains:

ModificationEstimated Wheel HP Gain
ECU Tune (UpRev)+22 hp
Cold Air Intake (Stillen Gen 3)+10 hp
Cat-Back Exhaust (Fast Intentions)+7 hp
Headers & HFCs (Motordyne + Fi HFC)+15 hp
Total (estimated)+54 hp

All figures are at the wheels. A stock 2011 G37 6MT typically dynos at 270–280 whp. With the above mods, you can expect 325–335 whp, translating to around 400 engine horsepower. That is easily 50+ hp over stock. Adding a lightweight flywheel and throttle body will not show significantly on the dyno but will transform the driving feel.

Cost of an OEM+ 50-HP Build

Budget for an effective OEM+ build that includes all major components:

  • ECU Tune (cable + license): $600–$800
  • Cold Air Intake: $300–$500
  • Cat-Back Exhaust: $800–$1,200
  • Headers & High-Flow Cats: $1,200–$1,800
  • Throttle Body: $300–$400
  • Lightweight Flywheel: $300–$500 (installation extra)
  • Supporting mods (oil cooler, mounts): $400–$700

Total parts cost: roughly $4,000–$5,500. Installation labor can add $1,000–$2,000 if you cannot do the work yourself. Compare this to the cost of supercharging the VQ37VHR (usually $6,000–$8,000 plus installation), and the OEM+ route provides excellent value with moderate power gains and stock-like daily manners.

Potential Pitfalls: What to Avoid

Even with careful planning, some common mistakes can compromise an OEM+ build:

  • Skipping the tune – Running intake and exhaust without a recalibration wastes power and can cause lean conditions at high RPM.
  • Over-oiling the air filter – Too much oil on a cotton filter can contaminate the MAF sensor, causing rough idle and throttle issues. Use dry filters if you are concerned.
  • Ignoring heat soak – Cold air intakes that sit near the engine without proper shielding can pull hot air, losing power. Ensure your intake has a good heat shield or is routed to the fender.
  • Choosing aggressive cams or cams without supporting mods – Camshaft swaps require internal engine work and often need forged pistons and springs. That is beyond OEM+ and introduces reliability concerns.
  • Using cheap “generic” headers – Poorly fitting headers can leak, melt wiring, or cause constant CEL. Stick to established brands like Motordyne, Z1, or Stillen.
  • Not checking local emissions laws – Removing catalytic converters may be illegal in your area. High-flow cats are often a safer choice for street-driven cars.

By avoiding these pitfalls, you will save time, money, and frustration.

Conclusion

Building a 50+ horsepower Infiniti G37 with OEM+ upgrades is entirely achievable without gutting reliability. Focus on the core breathing mods—intake, headers, exhaust, tune—and consider the throttle body and flywheel for extra responsiveness. Always use reputable parts from known vendors like Z1 Motorsports, Stillen, Fast Intentions, and Motordyne, and have the car professionally tuned. The result is a G37 that drives like a factory upgrade—faster, sharper, and more enjoyable, yet still comfortable and dependable for daily use. Start with the tune, then build outward, and you will join the thousands of G37 owners who have unlocked the true potential of the VQ37VHR.

External resources: Z1 Motorsports | Stillen | Fast Intentions | UpRev