Before You Begin: Understanding the HKS GT Supercharger System

The HKS GT Supercharger Kit is one of the most respected forced-induction systems for the Nissan 370Z (Z34 chassis). Built around a high-efficiency centrifugal supercharger, the kit delivers linear, reliable power gains without the heat-soak issues common with some turbo setups. Typical output with the standard GTS8550 supercharger unit is around 450–500 horsepower at the wheels on a stock VQ37VHR engine, depending on supporting mods and tuning.

This guide assumes you have intermediate mechanical experience and a fully equipped garage. While the kit is designed as a bolt-on system, installation still requires careful attention to detail, proper torque specs, and a thorough understanding of the VQ37’s cooling and fuel systems. If at any point you feel unsure, consult a professional performance shop. The HKS official installation manual should always be your primary reference.

Tools & Supplies Checklist

Beyond the obvious hand tools, having the right specialty items will make the job smoother and safer.

  • Standard hand tools: 3/8″ and 1/2″ drive socket sets, wrenches (10mm–19mm), Allen keys, Torx bits (T25, T30, T40)
  • Torque wrench (ft-lb and in-lb ranges) – critical for fasteners on the supercharger bracket and intake manifold
  • Jack and jack stands (capable of supporting the 370Z’s curb weight)
  • Coolant: Nissan long-life blue coolant or equivalent (approx. 2 gallons mixed 50/50 with distilled water)
  • Engine oil: 5W‑30 or 5W‑40 high‑quality synthetic (post‑break‑in; fill to spec after supercharger installation)
  • New gaskets: intake manifold gaskets, throttle body gasket, oil cooler seals (kit may include some, but have spares)
  • Vacuum hose: 5/32″ silicone hose for boost reference lines (if not included)
  • Safety gear: impact-resistant glasses, mechanic’s gloves, fire extinguisher nearby
  • Optional but helpful: coolant funnel, oil filter wrench, flashlight, shop vac, parts magnetic tray

Preparation: Getting the 370Z Ready

Work Area & Safety

Park on a level surface and disconnect the negative battery terminal. Allow the engine to cool fully – the VQ37’s aluminum block holds heat. Lift the car securely and place jack stands under the factory lifting points. Never rely on the jack alone.

Fluid Drain

  • Coolant: Place a drain pan under the radiator petcock (driver side, lower). Open the petcock and remove the radiator cap to speed drainage. Also drain the engine block drain plug (passenger side, near the starter) for complete evacuation.
  • Engine oil: Remove the drain plug and oil filter. Let it drain for at least 15 minutes. While the oil is out, you can inspect the oil pan gasket area for any leaks.

Removing Obstructions

Remove the engine undercover (if equipped), the strut tower brace (aftermarket or stock), and the air box assembly. Unbolt the engine beauty cover. Label and set aside all fasteners – this will save hours during reassembly. Disconnect the mass air flow (MAF) sensor and any harness clips on the intake tube.

Removing Stock Intake & Manifold

With access clear, you can now remove the factory intake components.

  1. Throttle body: Unplug the electrical connector, loosen the two 10mm bolts, and carefully lift the throttle body off. Use a clean rag to block the opening – you don’t want debris falling into the intake ports.
  2. Intake manifold: The stock manifold is held by multiple 10mm and 12mm bolts. Work in a crisscross pattern to avoid warping the plastic manifold. Disconnect the vacuum lines, PCV hose, and the brake booster line.
  3. Fuel rail: You do not need to remove the fuel rail entirely for the HKS kit, but carefully unclip the injector harness and move the harness out of the way. The factory fuel system is used; only the hard lines and regulator remain untouched.
  4. Oil cooler: The factory oil cooler (heat exchanger) is located above the oil filter. Disconnect the two coolant lines and the oil lines. You will replace this assembly with the HKS oil cooler adapter and remote filter mount (included in the kit). Save the factory parts if you need to revert.

Installing the HKS GT Supercharger Kit

Step 1: Mount the Supercharger Bracket

The HKS bracket replaces a section of the lower intake manifold support. Apply a thin coat of anti-seize to the bolts (especially those that thread into the aluminum block). Using the supplied bolts and the included gasket/seal, torque the bracket to 35 ft‑lb (47 N·m) as per the HKS manual. Ensure the bracket sits flush against the block – any misalignment could cause belt tracking issues.

Step 2: Attach the Supercharger Unit

Lift the supercharger (GTS8550) onto the bracket. There is a locating pin that helps align the unit. Install the four M8 bolts from the kit and torque them in a cross pattern to 18 ft‑lb (24 N·m). Connect the oil return line (from the supercharger to the oil pan) using the provided -10AN fittings. This step is critical: ensure the return line is not kinked and clears the chassis crossmember.

Step 3: Throttle Body & Intake Manifold

Reinstall the factory throttle body onto the new HKS intake manifold (which incorporates the supercharger inlet). Use a new gasket and torque the throttle body bolts to 7 ft‑lb (9 N·m). Carefully seat the manifold onto the engine using new manifold gaskets – there is a specific bolting sequence in the HKS instructions. Torque the manifold bolts in three stages to 15 ft‑lb (20 N·m). Connect all harnesses: throttle actuator, MAF sensor, IAT sensor, and boost solenoid (if present).

Step 4: Charge Piping & Blow‑Off Valve

The kit includes a polished aluminum charge pipe that runs from the supercharger outlet to the throttle body. Use silicone couplers and T‑bolt clamps – tighten to just snug, not bone‑crushing, to avoid cutting the silicone. The blow‑off valve (BOV) is typically mounted near the passenger side strut tower. Route the vacuum line from the BOV to a port on the intake manifold (not to the supercharger inlet – that would cause idle issues). Use thread tape on any NPT fittings for the boost reference.

Cooling System Rework

The supercharger generates significant heat, so a robust cooling setup is non‑negotiable.

  • Intercooler: The HKS kit uses an air‑to‑air intercooler that mounts in front of the radiator. Remove the front bumper cover to access the crash bar. Temporarily position the intercooler to mark mounting holes. Drill and bolt the intercooler using the supplied brackets. Connect the two charge pipes (turbo‑out to intercooler, intercooler to throttle body).
  • Radiator & Overflow: Reconnect the radiator hoses exactly as factory. Some kits include a lower radiator hose adapter for the coolant expansion tank – ensure the hose routing does not contact the supercharger belt.
  • Oil cooler: Mount the remote oil filter head and cooler sandwich plate using the HKS supplied adapter. Run the oil lines (braided stainless) to a quality oil cooler (if you choose to add one beyond the HKS kit, but the kit’s thermostatic plate works well for street use). Fill the engine with 5 quarts of oil, then with the engine off, crank it for 10–15 seconds to prime the oil system. Check for leaks at the oil filter adapter and cooler lines.

Belts, Tensioner & Final Mechanical Check

The HKS GTS8550 uses a dedicated drive belt. Install the supercharger belt over the pulleys. The tensioner is automatic (spring‑loaded), but you must confirm the belt is centered on all pulleys. Rotate the engine by hand with a 22mm socket on the crankshaft bolt – check for binding. If everything spins freely, proceed.

Reassembly & Fill Fluids

  • Refill the cooling system with 50/50 Nissan blue coolant and distilled water. Use a spill‑free funnel to burp air from the system. Idle the engine with the heater on high to cycle coolant – the VQ37 can be stubborn about air pockets. Top off as needed.
  • Fill the engine with the recommended oil (5W‑30 synthetic) and replace the oil filter (use a quality aftermarket filter like WIX or OEM Nissan). Do not overfill – run the engine, check the dipstick, and add until the level is between the marks.
  • Reinstall the battery, check all electrical connections, and secure any loose wiring with zip ties. Double‑check every fastener, especially on the intake manifold, supercharger bracket, and oil lines.

Starting & Initial Break‑In

Turn the key to the ON position for 5 seconds (prime the fuel pump) then crank. The engine should start quickly. Let it idle for 10 minutes – listen for any rattles, clunks, or air leaks. The supercharger will whine; that’s normal. Check for coolant and oil drips. If the idle is rough, inspect the MAF connection and the camshaft position sensors (they are easy to bump).

Once you’re confident there are no leaks, take the car for a gentle test drive. Avoid hard acceleration for the first 50 miles to allow the supercharger bearings and seals to seat. After that, you can perform a few full‑throttle pulls (on a closed course or dyno preferred) to verify boost pressure. The HKS kit typically runs 7–9 psi on the factory tune, but for safety you should use a piggyback ECU or a custom tune from a reputable shop like Z1 Motorsports or AMS Performance.

Tuning & Fuel System Considerations

The HKS GT kit includes a V2 boost controller and an optional fuel computer (F‑CON). A proper tune is mandatory – the factory ECU cannot handle the extra airflow and will run dangerously lean. Options include:

  • UpRev tuning: A common approach for 370Zs. UpRev allows flash tuning via the OBD2 port. Many shops offer base maps for the HKS kit. Expect to pay $500–$800 for a custom dyno tune.
  • HKS F‑CON iS: The HKS piggyback ECU is plug‑and‑play with the kit and provides fine control over fuel and timing. It’s more expensive but retains full factory safety features.
  • Standalone ECU: For high‑horsepower builds (above 500 whp), a Haltech or Motec ECU is recommended but not required for the basic kit.

Do not drive the car without a tune. Even 10 minutes of part‑throttle operation can cause knock and damage the VQ37’s thin cylinder walls.

Post‑Installation Maintenance Tips

  • Oil changes: The supercharger increases oil temperature. Change your oil every 3,000–4,000 miles with high‑quality synthetic. Consider adding an oil cooler after the kit if you track the car.
  • Belt inspection: Check the supercharger belt every oil change. The HKS belt tends to stretch slightly during the first 500 miles – you may need to re‑tension (the automatic tensioner compensates, but visually inspect for fraying).
  • Intake filter cleaning: The cotton air filter should be cleaned and re‑oiled every 15,000 miles (or more often in dusty conditions). A dirty filter restricts boost and robs power.
  • Intercooler care: After a track day or spirited drive, let the intercooler get airflow before parking. Heat soak from the radiator can reduce intercooler effectiveness.
  • Listen for changes: If the supercharger whine becomes a grind, or you notice boost fluctuations, inspect the couplers and the bypass valve. Small silicone coupler leaks are common – tighten all clamps periodically.

Common Mistakes & How to Avoid Them

  • Forgetting the oil return line gasket: The return line uses an O‑ring that can roll during installation. Grease it lightly to keep it seated.
  • Over‑tightening couplers: T‑bolt clamps can cut silicone hoses. Use a torque screwdriver set to 30 in‑lb (3.4 N·m) – that’s “snug plus a quarter turn.”
  • Not labeling vacuum lines: The kit has multiple ports. Mixing the BOV line with a manifold reference line can cause idle instability. Take photos before disconnecting.
  • Skipping the coolant bleed: The VQ37 is prone to air pockets in the rear cylinders. If you see the temp gauge spike, rev the engine to 3,000 rpm for 30 seconds to burp the system.

Performance Results & Real‑World Feedback

Owners report that the HKS GT supercharger transforms the 370Z from a naturally aspirated sports car into a serious power player. On a dyno, expect around 420 whp on a conservative tune with the 7‑psi pulley, and up to 500 whp with a 9‑psi pulley and supporting fuel upgrades. The centrifugal supercharger provides smooth, progressive power – no sudden boost spike like a turbo, which makes it very manageable on the street. Throttle response remains sharp, and the sound is intoxicating.

For comparison, a full‑bolt‑on 370Z with headers, exhaust, and tune makes about 320 whp. The HKS kit nearly doubles that figure, giving you usable power from 3,500 rpm all the way to the 7,500 rpm redline. Community discussions on My350Z highlight that reliability is excellent when the install is done correctly and the car is maintained. The key weak point is the factory clutch – you will almost certainly need an upgraded clutch (such as a South Bend Stage 2 or Competition Clutch) within the first 10,000 miles if you drive hard.

Final Words

Installing the HKS GT Supercharger Kit on your Nissan 370Z is a rewarding project that unlocks the true potential of the VQ37VHR engine. Take your time, follow the directions, and don’t skip the tune. With careful installation and proper maintenance, your supercharged 370Z will deliver miles of reliable, exhilarating performance. If you’re looking for further reading, check out the official HKS USA website for the latest kit revisions and tech bulletins. And as always, drive safe and respect the power.