Maximizing Your Miata’s Potential: The Jackson Racing M62 Supercharger for 150–200 HP

The Jackson Racing M62 supercharger has long been a benchmark upgrade for Mazda Miata enthusiasts who want a reliable, streetable power increase without the complexity of turbocharging. First introduced for the NA and NB chassis, this Eaton-based roots‑type blower is prized for its instant throttle response and linear power delivery. While the standard kit delivers roughly 140–160 wheel horsepower, many owners push beyond that into the 150–200 HP range by selecting larger supercharger pulley sizes and adding the right supporting modifications. This article breaks down the best size options, the engineering behind them, and all the ancillary upgrades needed to safely and consistently achieve those higher boost levels.

How the Eaton M62 Works in a Miata

The M62 is a positive‑displacement supercharger that displaces 62 cubic inches (about 1.0 liter) per revolution. It is driven via a cogged poly‑rib belt from the crankshaft; its internal rotors trap air and compress it against the outlet plenum. Unlike a centrifugal supercharger, the M62 builds boost almost instantly from idle, making the Miata feel significantly stronger at low and mid RPMs — exactly where the car needs it for daily driving and corner‑exit acceleration.

In the Jackson Racing kit, the M62 is typically paired with a cast manifold, a crossover pipe, and a dual‑throttle‑body setup on the NB or a single throttle body on the NA. The standard pulley ratio (crank pulley diameter ÷ supercharger pulley diameter) produces about 6–8 psi of boost on a 1.8‑liter engine. To reach the 150–200 HP target, you need to increase that ratio — but how much is too much?

Pulley Sizes and Corresponding Boost Levels

Jackson Racing offers a range of supercharger pulleys, and aftermarket manufacturers such as Flyin’ Miata and Track Dog Racing also supply alternative sizes. The critical factor is not just the pulley diameter but the drive ratio — the relationship between the crank pulley (typically 135–140 mm) and the blower pulley. Here is how different setups translate to boost and horsepower:

Small‑Diameter Pulley (≈ 80 mm) – ~150 HP

This is the “street” or “base” upgrade. With a crank pulley of 130 mm, an 80 mm blower pulley yields a drive ratio of about 1.625:1, producing roughly 6–7 psi on a 1.8‑liter engine. On a 1.6‑liter Miata, the same pulley will give slightly higher boost (7–8 psi) because of the smaller displacement. Power output is typically 145–155 wheel horsepower. This option is safe on a stock engine with no changes beyond a reflash or a piggyback ECU. It retains the factory air‑fuel ratio with standard injectors if the fuel pump is upgraded. Ideal for an owner who wants a noticeable bump without any internal engine work.

Medium‑Diameter Pulley (≈ 75 mm) – ~175 HP

Drop the blower pulley to 75 mm while keeping the stock crank pulley, and the drive ratio rises to about 1.73:1, boosting around 8–9 psi on a 1.8L. On a 1.6L, figure 9–10 psi. This level pushes the Miata into the 165–180 wheel horsepower range. At this point, the stock fuel system becomes marginal. You must upgrade to larger fuel injectors (e.g., 305–350 cc/min), a high‑flow fuel pump (Walbro 255 or equivalent), and a programmable ECU to trim the fuel map and adjust ignition timing. Many owners also fit an intercooler to keep intake air temperatures under control; while the M62 produces less heat than a turbo, sustained hard driving can lead to knock without charge cooling.

Large‑Diameter Pulley (≈ 67 mm) – ~200 HP

This is the limit of the M62 supercharger on a Miata without resorting to E85 or internal engine reinforcement. A 67 mm pulley with a 140 mm crank pulley gives a drive ratio of 2.09:1, pushing 11–13 psi depending on engine displacement and exhaust backpressure. Expect 190–210 wheel horsepower. To reach this level reliably, you need all the following: oversized injectors (550–650 cc), a return‑style fuel system or a robust aftermarket regulator, an efficient air‑to‑air intercooler (or water‑meth injection), a standalone ECU (Megasquirt, Hydra, or Adaptronic), and a clutch that can handle the torque. The engine’s compression ratio should ideally be lowered (e.g., 9.0:1 or lower pistons) if the car sees heavy track duty, though many street cars survive on pump gas with conservative tuning.

Matching Supercharger Size to Your Miata Engine

Two engine variants define the Miata world: the 1.6‑liter (1990–1993) and the 1.8‑liter (1994–2005). The M62 kit fits both, but the boost response and reliability trade‑offs differ.

1.6‑Liter Engines (B6)

The smaller displacement means the supercharger spins faster to move the same mass of air. For a given pulley, a 1.6L will see about 1–2 psi more boost than a 1.8L. The smaller engine also has less internal strength: early 1.6 blocks and connecting rods are weaker than the later 1.8s. If you target 200 HP on a 1.6L, you are essentially doubling the factory output. That stresses the rods and main bearings, so a forged rod and piston set becomes advisable. Many builders recommend staying at 170–180 HP on a stock 1.6L to avoid injecting rods through the block.

1.8‑Liter Engines (BP4W, BP-Z3)

The 1.8L engine is more robust, with forged connecting rods starting in 1999 and a stronger block architecture. It can comfortably handle 200 HP with the M62 if properly tuned and supported. The VVT version (2001–2005) can be tricky because the variable valve timing can cause detonation if not accounted for in the ECU. However, with proper cam timing maps, the VVT engine can actually make more midrange torque than the non‑VVT version. For 200 HP, the 1.8L is the ideal platform.

Supporting Modifications: What You Absolutely Need

Reaching 150 HP requires few changes; reaching 200 HP demands a systematic approach. Here is a prioritized list for each power level.

150‑HP Support Set (Base)

  • Fuel pump: A Walbro 190 or 255 lph pump ensures enough flow for the higher boost.
  • Engine management: A piggyback like the Megasquirt PNP2 or a simple timing controller is sufficient. Many Jackson Racing kits originally came with a PowerCard that works fine up to ~150 HP.
  • Cooling: Upgrading the radiator (e.g., Koyo 37 mm) prevents coolant temps from climbing during spirited driving.
  • Exhaust: A 2.25” or 2.5” cat‑back system reduces backpressure, helping the supercharger move air more efficiently.

175‑HP Support Set (Medium)

  • Injectors: 305–350 cc (RX‑8 yellow injectors or Bosch EV14).
  • ECU: Full standalone — Megasquirt MS3, Adaptronic, or a re‑tuned factory ECU (through ChipTorque).
  • Intercooler: A small air‑to‑air intercooler (e.g., Track Dog Racing “Big Boy”) sized to fit without cutting the bumper support. Expect 2–3 psi pressure drop, but huge intake temp reductions.
  • Clutch: A stage 1 clutch (e.g., ACT HD) to handle the increased torque.
  • Belt tensioner: The stock tensioner can slip at higher boost. An aftermarket manual tensioner or a pulley with a larger contact area helps.

200‑HP Support Set (Full Build)

  • Injectors: 550–650 cc high‑impedance injectors.
  • Fuel system: Return‑style with an AFPR or a surge tank for consistent delivery.
  • Intercooler: Efficient 500+ HP core (e.g., Bell Intercooler or custom). Water‑methanol injection can be used as an alternative.
  • ECU: Fully programmable with MAP sensor, knock control, and boost‑compensated fuel and timing.
  • Internal engine: Forged rods (e.g., Manley H‑beam), forged pistons (9.0:1 or lower), and ARP head studs.
  • Oil cooler: A thermostatic oil cooler is highly recommended – the supercharger adds significant heat to the engine oil.
  • Drivetrain: A stronger clutch (stage 2 or 3) and possibly a 1.8‑liter rear differential with upgraded axles if you have a 1.6L.

Installation Considerations for the M62 Kit

Jackson Racing’s instructions are comprehensive, but a few points deserve emphasis:

  • Belt alignment: Misalignment of the supercharger pulley to the crank pulley is the most common cause of belt throwing. Use a straightedge and check the pulley faces. They must be parallel within 0.5 mm. The kit includes spacers; do not skip this step.
  • Bracket rigidity: The M62 mounting bracket can flex under high boost, especially with a 67 mm pulley. Consider reinforcing it with a support bracket that ties to the engine block or using a Track Dog Racing reinforcement plate.
  • Clearance: On NB Miatas, the supercharger sits close to the brake master cylinder. The 67 mm pulley may require slight massaging of the bracket or relocation of the clutch master cylinder.
  • Idler pulleys: Adding an idler on the slack side of the belt reduces vibration and prevents slip. Some aftermarket kits include this.
  • Oil feed/drain: The M62 has internal bearings that are splash‑lubricated from the supercharger oil. For high‑boost use, check the oil level after every oil change. Some owners convert to a self‑contained oil system (using a separate reservoir) but that is not needed for street duty.

Tuning: The Make‑or‑Break Factor

A supercharger that is poorly tuned can destroy an engine in minutes. Even more than the hardware, the ECU calibration determines whether your 200‑HP Miata is a joy or a grenade.

  • Air‑Fuel Ratio: Under boost, target 11.5–12.0:1 for safety. Leaner than 12.5:1 at high load invites detonation.
  • Ignition Timing: Retard timing under boost. A typical 1.8L with 10‑12 psi might need 8–10 degrees of total advance at peak torque, ramping up to 14–16 degrees at redline.
  • Boost Control: The M62 is fixed‑displacement, so boost is determined purely by pulley size and engine RPM. You cannot “turn it down” with a boost controller unless you add a bypass valve or a restrictor plate – which is uncommon. That means you must tune for the maximum boost the pulley produces at redline.
  • Knock Detection: Use a knock sensor (most aftermarket ECUs support one) and log knock events. Even slight detonation will hammer rod bearings over time.
  • E85: If you can run E85, you can safely run 200 HP on a stock 1.8L engine without internal modifications – the ethanol’s octane rating (105–110) is game‑changing. You will need larger injectors (roughly 30% more flow) and a fuel system that can tolerate ethanol, but it is the cheapest way to avoid engine failure.

A reputable tuner experienced with Miatas – such as those at Flyin’ Miata or independent shops like Pakshole Motorsports – should handle the final calibration. Many remote tuning services exist for Megasquirt users.

Reliability and Long‑Term Maintenance

The Eaton M62 supercharger itself is notoriously durable, often lasting >100,000 miles without rebuild if the oil is changed regularly (every 30,000 miles using Jackson Racing’s synthetic oil). However, the rest of the car may not be as forgiving:

  • Cooling system: The Miata’s stock cooling system is marginal even in stock form. A good radiator, fresh coolant, and a properly working fan are mandatory. On track days, a larger radiator (Koyo 55 mm) and an oil cooler are wise.
  • Belt life: Poly‑rib belts driving a supercharger at high ratio wear faster. Inspect monthly and replace every 15,000–20,000 miles. A worn belt can slip, causing boost to spike and then drop, leading to idle issues.
  • Bypass actuator: The M62 kit uses a bypass valve that opens at idle and part throttle. If it sticks closed, you’ll have a parasitic loss; if it sticks open, you lose boost. Check its operation by sucking on the vacuum line – it should click firmly.
  • Oil leaks: The M62 mounts such that oil from the valve cover can drip onto the hot exhaust. Ensure the cam cover gasket is fresh and the PCV system is working.

Cost Considerations and Alternatives

A complete Jackson Racing M62 kit (used) can be found for $1500–$2500. Adding the medium pulley, injectors, and a standalone ECU pushes the budget to $3500–$4500. For the 200‑HP full build with internals, expect $6000–$8000. Compare this to a turbocharger system (e.g., Flyin’ Miata Voodoo II or Garrett kit) that delivers similar power for roughly the same or slightly less money. Turbochargers offer more peak horsepower potential and better highway efficiency, but they have lag and heat‑soak challenges. The M62’s immediate throttle response is its greatest asset – it makes the Miata feel like a naturally aspirated engine that happens to be much larger.

If you prefer a supercharger but want even higher RPM capability, consider the Rotrex C30‑74 or C38‑81 kits. They are centrifugal, meaning boost builds progressively with RPM, and they can exceed 250 HP. However, they lack the low‑end grunt of the M62.

Conclusion — The Right Size for Your Goals

For a street‑focused Miata that rarely sees a track, the medium pulley (75 mm) combined with a proper ECU and intercooler offers the best balance of power (170–180 HP) and reliability without touching internal parts. This gives you a car that is significantly faster than stock yet still docile in traffic.

If you are building a dedicated track car or want to chase every last pony, the 67 mm pulley can deliver 200 HP, but only with the full suite of supporting modifications. Do not skimp on the ECU tuning or the fuel system – your connecting rods will thank you.

The M62 supercharger remains a fantastic way to wake up a Miata. By choosing the right pulley size and investing in the proper hardware and calibration, you can enjoy a reliable, responsive 150–200 HP sports car that punches far above its weight.