Understanding Your Infiniti’s Baseline Performance

Before you modify a single bolt, you must know exactly what your Infiniti is capable of from the factory. Each model—whether it’s a Q50, Q60, G37, or QX70—comes with a specific engine, transmission, final drive ratio, and electronic speed limiter. Check your owner’s manual or the vehicle’s information sticker for the factory-rated horsepower, torque, and top speed (often listed as “maximum speed” or governed). Many modern Infinitis have an electronic limiter set around 130–155 mph to protect the drivetrain and tires. Removing or raising that limiter is one of the most direct ways to increase top speed, but it requires supporting modifications to keep the car safe.

Also note your Infiniti’s engine family: the VQ37VHR (used in many G37 and early Q models), the VR30DDTT (twin-turbo in later Q50/Q60), or the 5.6L VK56 (in QX80 and some Q70). Each responds differently to modifications. Factory specifications also include the transmission type—7-speed automatic (RE7R01A or JR710E) or 6-speed manual. Knowing these details helps you select the right parts and tuning strategy. A thorough baseline includes checking your vehicle’s health: compression test, fluid condition, and any existing fault codes. Starting with a well-maintained car is non‑negotiable for safe speed increases.

Engine Air Intake and Exhaust Upgrades

Improving airflow into and out of your engine is the most common first step. A high-flow cold air intake replaces the restrictive factory airbox and air filter, drawing cooler, denser air from outside the engine bay. This can add 5–10 horsepower on naturally aspirated VQ engines and slightly more on turbocharged VR engines because it also reduces intake restriction. Look for a kit with a heat shield and a dry or oiled cotton filter that is washable. Pair it with a larger diameter intake tube and a high-flow MAF sensor housing if your tune requires it.

On the exhaust side, a cat-back exhaust system reduces backpressure and improves scavenging. Systems with mandrel-bent tubing and a free-flowing muffler (or dual mufflers) can free up 8–15 horsepower. For more aggressive gains, replace the exhaust headers or downpipes. On the VR30 twin-turbo engine, aftermarket downpipes with high-flow catalytic converters or catless downpipes significantly lower turbo spool time and allow for more boost. However, ensure any exhaust modification complies with Tennessee emissions laws—catalytic converters may be required for road legality. Professional installation is advised to avoid exhaust leaks that could affect oxygen sensor readings.

Intake Manifold and Throttle Body

If you are building for top speed, consider upgrading the intake manifold and throttle body on naturally aspirated engines. A ported or aftermarket intake manifold (like those from Motordyne or Z1 Motorsports) improves airflow distribution, while a larger diameter throttle body (e.g., 75mm or 80mm) lets the engine breathe more freely at high RPM. These modifications work best when combined with ECU tuning. Be aware that they can shift the powerband upward, which may require higher RPM to see benefits at top speed.

ECU Tuning – The Most Critical Upgrade

Modern Infiniti engines are heavily controlled by the Engine Control Unit (ECU). Factory calibration prioritizes fuel economy, emissions, and drivetrain protection, often leaving significant untapped power. Custom ECU tuning remaps fuel tables, ignition timing, throttle response, and—on turbocharged models—boost pressure. For naturally aspirated engines, a reflash can raise the rev limiter, adjust variable valve timing, and optimize air-fuel ratios for higher RPM power, directly increasing top speed. For VR30 twin-turbo engines, tuning can safely increase boost from the factory ~7–9 psi to 14–16 psi with the right supporting mods, yielding 100+ horsepower gains.

There are two main paths: a handheld tuner with pre-loaded maps (like an Ecutek or Cobb Accessport) or a custom dyno tune. A dyno tune is always preferred for safety and performance because the tuner can monitor knock, fuel pressure, and exhaust gas temperatures in real time. Many well-known Infiniti tuners operate remotely or are located in the Southeast; some even travel to events at Nashville Superspeedway. Ensure your tune disables or raises the electronic speed limiter and adapts your transmission shift points if needed. Do not run a tune without verifying that your fuel system (injectors, fuel pump) can support the increased power.

Forced Induction and Boost Control

For the highest top speed gains, adding a supercharger or turbocharger to a naturally aspirated VQ engine, or upgrading the turbos on a VR30, yields dramatic results. A centrifugal supercharger kit (e.g., from Stillen or Vortech) can push a VQ37 to 500+ whp, while a big single turbo system can exceed 600 whp. With the VR30, upgraded turbochargers (e.g., from Z1 or GTM) combined with methanol injection and a fuel system upgrade can support well over 700 whp. However, forced induction requires meticulous attention to cooling and engine internals to avoid catastrophic failure at sustained high speeds.

If you are aiming for top speed runs (e.g., over 180 mph), consider upgrading the intercooler (or adding a larger one), installing an oil cooler, and possibly upgrading pistons and connecting rods on higher boost applications. A quality boost controller integrated with the ECU tune allows you to adjust pressure safely. Always check your engine’s compression and use a wideband oxygen sensor to monitor air-fuel ratios during the initial runs.

Drivetrain Upgrades for High-Speed Stability

Your Infiniti may have an electronic speed limiter in the transmission or differential. With the 7-speed automatic, a transmission tune that adjusts shift firmness and line pressure is crucial for handling higher torque. Many owners swap to a higher stall torque converter for better acceleration, but for top speed, you want the converter to lock up quickly to minimize slippage. The final drive ratio also matters: numerically lower gears (e.g., 3.13:1 vs 3.69:1) reduce engine RPM at a given speed, allowing a higher top speed if the engine has enough power to overcome aerodynamic drag. Some enthusiasts swap to a taller final drive from a different model (e.g., Q70) to extend top speed on the highway.

Reinforce the differential with a limited-slip differential (LSD) if your car does not have one. A quality LSD (e.g., Quaife or OS Giken) improves traction under hard acceleration and cornering, essential when approaching high speeds on a track. Upgrade the half shafts and axles if you are exceeding 500 whp to prevent breakage.

Suspension and Chassis Tuning

High speed demands stability. A soft, stock suspension allows body roll and weight transfer that can become dangerous over 130 mph. Install coilover suspension with adjustable dampers and ride height. Brands like KW, Ohlins, and BC Racing offer Infiniti‑specific kits. Lowering the car slightly reduces aerodynamic drag and lowers the center of gravity. Add stiffer anti‑roll bars (sway bars) front and rear to minimize body roll during lane changes or crosswinds.

Upgrade bushings throughout the front and rear subframes to polyurethane or solid units. This reduces slop and improves steering response. A front strut tower bar and rear chassis brace tie the unibody together, preventing flex that can cause unpredictable handling at high speed. Finally, a proper performance alignment with maximum negative camber in the front (roughly -1.5 to -2.0°) and a slight toe‑in at the rear improves high‑speed stability but may increase tire wear.

Brake System Upgrades – Safety First

Increasing top speed means you need to slow down from higher speeds repeatedly. Factory brakes may fade after a few hard stops from 140+ mph. Upgrade to a big brake kit (BBK) with larger rotors (e.g., 14‑inch or 15‑inch) and multi‑piston calipers from Brembo, StopTech, or Wilwood. Choose slotted or drilled rotors for better heat dissipation. High‑performance brake pads with a high temperature rating (like Ferodo DS2500 or Pagid RSL1) and DOT 4 or 5.1 brake fluid with a high boiling point (over 600°F dry) are essential.

Do not overlook brake cooling. Ducting from the front bumper to the rotors helps keep temperatures in check during sustained high‑speed runs. If your car is equipped with electronic brake assist or stability control, ensure that those systems work properly with the upgraded hardware. A safety note: never go faster than your brakes can handle.

Tires and Wheels for Top Speed

Your tires are the only contact patch with the road. For speeds above 150 mph, you need tires with a speed rating of Z (over 149 mph) or W (up to 168 mph), ideally Y (up to 186 mph). Summer performance tires like Michelin Pilot Sport 4S or Continental ExtremeContact Sport offer excellent grip and stability at high speed. Ensure load rating matches your vehicle’s weight. Check tire pressure frequently; even a few PSI difference can affect stability.

Wheels should be lightweight and strong, such as forged alloys from brands like Enkei, Rays, or BBS. Reducing unsprung weight helps acceleration and braking. Get a proper wheel alignment after installing new wheels and tires. Also consider wheel studs and lug nuts of adequate strength—ARP extended studs are common for track‑oriented Infinitis.

Weight Reduction

Less weight means higher top speed and better acceleration. Remove unnecessary interior items: spare tire, rear seats (if not needed), sound deadening materials, and heavy floor mats. Install lightweight racing seats (e.g., Recaro Pole Position or Bride) and a lighter battery (lithium‑ion or Odyssey PC680). Carbon fiber body panels, such as a hood or trunk lid, reduce weight over the crucial front axle. Every 100 pounds saved can translate to a small increase in top speed and better handling.

Tennessee law strictly prohibits street racing and exceeding posted speed limits. The Nashville Metro area has a zero‑tolerance policy for reckless driving, with penalties including fines, license suspension, and even vehicle impoundment. Do not test your Infiniti’s top speed on public roads. Instead, use a controlled facility such as:

  • Nashville Superspeedway in Lebanon (about 30 minutes east of downtown). They offer track days, high‑performance driving events, and occasionally open‑track sessions where you can safely explore your car’s limits.
  • Music City Dragway in Nashville offers a 1/4‑mile track. While not a top‑speed venue, you can test acceleration and braking in a safe environment.
  • Lucas Oil Raceway in Indianapolis (about 5 hours north) has longer straights suitable for high‑speed events.

Always verify your modifications with Tennessee’s vehicle inspection requirements: any modification that deletes catalytic converters or bypasses emissions equipment can lead to a failing inspection and fines. Keep all receipts for parts and professional labor to show compliance if needed.

Ongoing Maintenance for Performance

High‑speed driving places extreme stress on your Infiniti. After each track day or speed session, perform the following:

  • Engine oil change: Use a full synthetic with a higher viscosity (e.g., 5W‑40) if you track frequently. Check oil pressure and temperature gauges.
  • Cooling system: Flush coolant and upgrade to a higher capacity radiator if you notice overheating. Consider a lower thermostat for more consistent temperatures.
  • Spark plugs: On VR30 engines, change plugs more often (every 15,000 miles or after heavy tuning) to avoid misfire at high boost.
  • Fuel system: Clean injectors and check fuel pressure. On high‑power builds, upgrade to a return‑style fuel system with a larger pump.
  • Transmission and differential fluids: Switch to a high‑quality synthetic that can withstand higher temperatures (e.g., Motul or Redline). Change every 30,000 miles or after a season of track use.

Final Recommendations

Increasing your Infiniti’s top speed safely is a systematic process. Start with the basics: ensure the car is in perfect mechanical condition, then improve airflow with intake and exhaust, unlock power with ECU tuning, and finally address suspension, brakes, and tires. Never skip the safety upgrades, and always test at a track. Nashville offers excellent venues to push your car legally. With careful planning and professional help, you can enjoy thrilling speed while keeping yourself and others safe on the road.

For further reading, consult Infiniti’s official website for model specifications, Tennessee Department of Safety for traffic laws, and Z1 Motorsports for quality performance parts specific to Infiniti vehicles.