Before You Start: Understanding the Flyin’ Miata Stage 2 Supercharger

The Flyin’ Miata Stage 2 Supercharger Kit is one of the most popular forced-induction upgrades for the NB Miata (1999–2005). It uses a Rotrex C30‑74 supercharger paired with an intercooler, delivering a reliable power increase from the stock 140 hp to approximately 200–210 whp on a stock engine. This kit is designed to be a bolt‑on affair, but a careful, methodical installation is essential for longevity and performance.

This guide expands on the basic six‑step process, adding detailed torque specs, wiring tips, coolant bleeding procedures, and common pitfalls to avoid. We’ll also cover post‑install tuning and break‑in requirements. Plan for a full weekend if you’re working alone; having a helper for lifting the supercharger into place is recommended.

Step 1: Gather Tools, Materials, and Workspace Requirements

Necessary Tools

Missing a single tool mid‑install can waste hours. Assemble everything before you start:

  • Flyin’ Miata Stage 2 Supercharger Kit – Verify all parts are present against the included parts list. Common missing items: a specific bracket bolt or an intercooler coupler.
  • Metric socket set – 8mm, 10mm, 12mm, 14mm, 17mm, 19mm sockets (deep and shallow).
  • Combination wrenches – same sizes plus 21mm for crank pulley bolt.
  • Torque wrench – ¼‑inch drive for small fasteners (in‑lbs) and ⅜‑inch or ½‑inch drive for larger bolts (ft‑lbs).
  • Allen keys (hex bits) – 5mm, 6mm, 8mm for supercharger mounting.
  • Zip ties – various sizes for routing hoses and wiring away from heat sources.
  • Shop towels, brake cleaner, and a wire brush – to clean mounting surfaces.
  • Coolant – 50/50 pre‑mixed or concentrate + distilled water (about 2 gallons). Note: NB Miatas use FL22 or standard ethylene glycol; check your year.
  • Engine oil – 5W‑30 or 10W‑30 (consult your climate) and a new oil filter (Mobil 1 or OEM Mazda).
  • Jack and jack stands – for wheel removal if needed.
  • Floor jack (optional but helpful for raising the engine slightly).
  • Drill with 3/8” bit – for a small accessory bracket hole (if required by your kit version).

Workspace Prep

Park the car on a level, concrete floor. Let the engine cool completely (2–3 hours after last drive). Disconnect the negative battery terminal first, then the positive. Remove the battery entirely to improve access to the passenger side of the engine bay. Have a fire extinguisher nearby and ensure good ventilation if working indoors.

Step 2: Prepare the Miata – Remove Stock Components

This step involves removing the factory intake, throttle body, and belts. Take photos or label everything—you’ll be reinstalling some parts later.

2.1 Remove the Engine Cover and Intake

Unbolt the decorative plastic engine cover. Remove the airbox and intake tube assembly (use a flathead to loosen the MAF sensor retaining clip; be gentle with the plastic). Disconnect the mass airflow (MAF) sensor connector. Set aside the intake system—some parts remain in place, like the air filter housing, but the crossover tube goes.

2.2 Remove the Throttle Body (Optional but Recommended)

On NB Miatas, the throttle body sits on the intake manifold. The supercharger bracket replaces the stock throttle body mounting location. Remove the throttle body with the two 12mm bolts. Important: Do not lose the tiny gasket behind it—it can be reused if still pliable. Cover the intake manifold opening with a clean towel to prevent debris entry.

2.3 Drain Coolant and Remove Radiator (If Needed)

The Flyin’ Miata Stage 2 kit includes an intercooler that mounts in front of the radiator. You can install the intercooler without removing the radiator if you have enough clearance, but many installers find it easier to remove the radiator (two 10mm bolts at top, two 8mm bolts at bottom). Drain the coolant at the petcock (passenger side, lower radiator tank) into a clean container for reuse if not contaminated. If you remove the radiator, also unplug the coolant temperature sensor and the fan connectors.

2.4 Remove Serpentine Belt and Accessories

The supercharger drive belt replaces the AC/alternator belt. Loosen the alternator pivot bolt and the locking bolt, then pivot the alternator inward to release belt tension. Slip off the belt. You may also need to remove the AC compressor bracket bolts (not the AC lines) to mount the supercharger bracket. Mark the positions of the idler pulleys with a grease pen.

Step 3: Install the Supercharger Bracket

This is the most critical step for alignment. The bracket must be torqued precisely and sit flush against the engine block.

3.1 Clean Mounting Surfaces

Use brake cleaner and a rag to remove any oil, grease, or old gasket material from the engine block where the bracket mounts. Pay attention to the front of the engine near the water pump and timing cover.

3.2 Position the Bracket

Slide the billet aluminum bracket into place. It replaces the AC compressor bracket and also mounts to two lower holes on the side of the engine. Use the supplied bolts: typically M10x1.25 for the main holes and M8x1.25 for the smaller ones. Do not use thread locker on every bolt – only those that go into aluminum (medium strength Loctite 243) and follow the Flyin’ Miata instructions for specific bolts.

3.3 Torque Bolts in Sequence

Torque the M10 bolts to 30–35 ft‑lbs (using a 6‑point socket). Torque the M8 bolts to 18–20 ft‑lbs. Use a criss‑cross pattern to avoid warping the bracket. Verify that the bracket is square to the engine: the supercharger mount surface should be parallel to the front of the engine. If it is misaligned, you may have a wrong‑size bolt or an obstruction (check for leftover AC bracket spacers).

3.4 Install Idler Pulley and Belt Tensioner

The kit comes with a dedicated idler pulley and a manual tensioner (turnbuckle style). Bolt the idler pulley onto the bracket using the supplied spacer and M8 bolt. Do not fully tighten yet. Install the tensioner assembly loosely—you will adjust it after the supercharger is mounted.

Step 4: Attach the Supercharger Unit

The Rotrex supercharger is heavy (about 15 lbs). Use a helper or a strap to hold it while you align the mounting bolts.

4.1 Prep the Supercharger

Remove the shipping plugs from the Rotrex unit. The kit includes an oil feed line (for the Rotrex’s dedicated oil system) and a return line. Important: The Rotrex must never run without oil. Do not rotate the supercharger by hand until the oil lines are connected. If you accidentally rotate it, you may damage the internal clutches. Attach the oil feed and return hoses now (they use AN fittings; tighten with a wrench, not excessive torque). Route the hoses away from exhaust heat.

4.2 Mount the Supercharger

Slide the supercharger onto the bracket studs (or bolt holes). Use the provided M10 bolts and washers. Torque to 30 ft‑lbs in two stages: first snug, then final torque. Check that the pulley aligns with the idler pulley and crankshaft pulley. The belt should run straight; if it’s cocked, you may need to shim the bracket or adjust the idler.

4.3 Install the Belt

Route the new serpentine belt around the crank pulley, supercharger pulley, and idler pulley. Use the tensioner to take up slack. Tighten the tensioner bolt (typical torque: 18 ft‑lbs). Rotate the engine by hand (use a breaker bar on the crank bolt) to ensure the belt tracks correctly. Readjust tension if you hear slipping.

Step 5: Connect Hoses, Wiring, and Intercooler

Now the supercharger is mounted, but it needs its life support systems: intercooler piping, coolant hoses, vacuum lines, and electrical connections.

5.1 Intercooler Installation

The Flyin’ Miata Stage 2 includes an air‑to‑air intercooler that mounts in front of the radiator. Position the intercooler in the lower opening of the bumper bar. You may need to trim the plastic undertray slightly for clearance. Use the included brackets (attach to frame horns with self‑tapping screws). Connect the aluminum piping: from the supercharger outlet to the intercooler, then to the throttle body. Use T‑bolt clamps (torque to about 30 in‑lbs). Ensure all silicone couplers are fully seated and not kinked. Pro tip: Apply a tiny amount of hairspray to the intercooler pipe ends to make the couplers slide easier and hold better.

5.2 Coolant Lines

Some Stage 2 kits include a coolant reroute for the supercharger’s water‑cooling jacket. Locate the coolant hoses supplied. One connects to the engine water outlet (passenger side), the other to the water inlet near the thermostat. Use spring‑type clamps (supplied) – never use worm‑gear clamps on plastic fittings. Fill the system with coolant now (you’ll bleed air later).

5.3 Vacuum Lines

Run a boost‑referenced vacuum line from the intake manifold (after the throttle body) to the bypass valve on the supercharger. Use silicone hose; secure with small zip ties. Also connect the MAP sensor (if your kit includes a different sensor). The Flyin’ Miata instructions show a split‑second vacuum routing: tap into the brake booster line with a T‑fitting. Avoid routing near hot EGR tubes.

5.4 Electrical Connections

The Stage 2 kit usually includes a wiring harness for the supercharger’s temperature sensor (if equipped) and an optional air‑fuel ratio gauge. Connect the sensor wires to the supplied pigtail – use solder and heat shrink (not butt connectors). Secure the harness along the factory wire looms with zip ties.

5.5 Reinstall Throttle Body and Intake

Mount the throttle body onto the new intake manifold adapter (provided). Use a new gasket or RTV sealant. Connect the throttle cable – adjust the cable bracket to prevent slack. Reinstall the airbox and MAF sensor. The stock intake tube may need a slight trim to fit over the supercharger inlet; use a sharp knife or sawzall. Ensure the MAF sensor is oriented with the arrow pointing towards the engine.

Step 6: Final Checks, Bleed Coolant, and First Startup

Before turning the key, double‑check every fastener and hose.

6.1 Visual Inspection

  • Rotate the engine by hand (breaker bar on crank bolt) – feel for resistance. Should turn smoothly through two full revolutions.
  • Check belt tension: push down on the longest span between pulleys. Deflection should be about ½ inch with moderate pressure.
  • Ensure all wiring is away from moving parts and exhaust manifold.
  • Reconnect battery terminals (positive first, then negative).

6.2 Fill and Bleed Coolant

Fill the radiator with 50/50 coolant. Open the bleed screw on the thermostat housing (a small 10mm bolt) until coolant streams out, then close it. Run the engine at idle with the radiator cap off, heater set to full hot, and fan off. Watch for bubbles. When the thermostat opens (upper radiator hose gets hot), add more coolant. Replace the cap. You may need to do this procedure twice after a test drive.

6.3 Check Oil and Rotrex Oil System

The Rotrex supercharger has its own oil reservoir (supplied). Fill it to the dipstick mark with the special Rotrex oil (not engine oil). Start the engine for 10 seconds, then stop and recheck the dipstick. Add oil as needed. Also check engine oil level – fill as necessary.

6.4 First Startup and Tuning

Start the engine. Listen for unusual noises – a supercharger whine is normal, but grinding or screeching indicates misalignment. Check for coolant and oil leaks. Let the engine reach operating temperature. Important: The Flyin’ Miata Stage 2 kit requires a standalone ECU or a reflash. If you are using the stock ECU with the included plug‑and‑play piggyback (like the Voodoo Box), follow the fuel pressure adjustment instructions. Do not drive hard until the fuel trims are verified with a wideband O2 sensor.

Recommended first drive: short, low‑load trips (2–3 miles) to allow the ECU to learn. Then perform a few gradual pulls in 3rd gear from 2,500 to 5,000 rpm, not exceeding 5 psi of boost. Log air‑fuel ratios – they should stay between 12.0 and 13.0 under boost. If you see lean spikes (AFR above 13.5), stop immediately and adjust fuel pressure or timing.

Post‑Installation: Tuning and Maintenance

Fuel System Upgrades

For Stage 2, Flyin’ Miata recommends a 255‑liter‑per‑hour fuel pump and optional 550cc injectors. If you retain stock injectors, the Voodoo Box will pull timing under boost to prevent detonation. For maximum safety, take the car to a dyno tuner with a wideband and a roll‑road. Expect to spend an hour dialing in the boost curve.

Reliability Tips

  • Change engine oil and filter every 3,000 miles (use synthetic 5W‑30).
  • Inspect supercharger oil level every oil change.
  • Check belt tension monthly – the belt can stretch in the first 500 miles. Re‑tension if you see more than ¾ inch deflection.
  • Replace spark plugs with one range colder (NGK BKR7E) and gap to 0.030” to prevent misfire under boost.

Common Issues and Solutions

  • Whine too loud: Check supercharger mounting bolts – they may be loose. Also ensure the belt is not rubbing against a bracket.
  • Low boost (under 6 psi): Possible belt slip. Tighten tensioner. Ensure intercooler piping is not leaking (listen for hissing).
  • Check engine light on first start: Usually a vacuum leak. Double‑check all intake couplers and the bypass valve hose.
  • Coolant overflow tank overflowing: Air trapped in system. Bleed again with the car on a ramp (nose up).

To supplement this guide, consult the official resources:

With careful installation and proper tuning, your NB Miata equipped with the Flyin’ Miata Stage 2 Supercharger will deliver reliable, grin‑inducing power for thousands of miles. Take your time, double‑check every step, and enjoy the transformation.