Building a high-performance car on a tight budget is a challenge that separates dreamers from doers. The 13B-REW swap has earned a legendary reputation among enthusiasts who want rotary power without the price tag of a factory twin-turbo RX-7. This guide covers a realistic, step-by-step approach to installing a 13B-REW engine in your vehicle for under $3,000 while targeting a solid 350 horsepower.

Why the 13B-REW?

The 13B-REW is Mazda’s most iconic rotary engine. Found in the third-generation RX-7 (FD3S), it features twin sequential turbochargers, a lightweight aluminum housing, and a high-revving character that no piston engine can match. Key attributes include:

  • 1.3-liter displacement with a power-to-weight ratio that shames many larger engines
  • Stock output around 280 hp — easily pushed to 350 hp with modest upgrades
  • Extremely compact and light (roughly 280 lbs with accessories), simplifying installation in almost any chassis
  • High-revving capability — safe to 9,000 RPM with proper cooling and oiling

For a budget build, the 13B-REW offers a unique blend of novelty, performance, and tunability. Many engine swaps start with a cheap junkyard LS, but the rotary delivers a driving experience that is genuinely different.

Budget Reality Check: Under $3,000

A $3,000 budget for a turbocharged engine swap is extremely tight. You will need to source parts used, do your own labor, and make smart compromises. Here’s a realistic breakdown:

  • 13B-REW engine (complete with turbos, intake, manifolds): $1,200 – $1,800
  • Transmission (RX-7 T56 or adapter for your car’s gearbox): $400 – $700
  • Wiring harness and ECU (used stock ECU or basic standalone): $300 – $500
  • Engine mounts, intercooler piping, coolant hoses: $200 – $400
  • Fuel pump, injectors, lines: $150 – $250
  • Consumables (oil, coolant, gaskets, fluids): $100 – $200

Total estimate: $2,350 – $3,850. To stay under $3,000 you must hunt for deals, reuse your existing transmission if possible, and skip unnecessary frills. A junkyard 13B-REW with a rebuild kit is the most cost-effective path.

Sourcing the Engine and Parts

Finding a 13B-REW

Look for complete front clips or engine packages from crashed FD3S RX-7s. Check RX7Club forums, local Facebook Marketplace, and import salvage yards. Avoid engines with known apex seal failure — ask for a compression test or buy a non-running core for a rebuild.

What to Buy with the Engine

Try to get the following included in your purchase:

  • Complete intake and exhaust manifolds
  • Stock twin turbos (they are fine for 350 hp)
  • Engine wiring harness and ECU (even if modified, it saves time)
  • Alternator, starter, and power steering pump

If you can’t find a full package, be prepared to spend extra on these parts individually, which can blow your budget.

Vehicle Preparation

Before the 13B-REW goes in, prepare the chassis. This stage is critical for a clean swap that doesn’t nickel-and-dime you later.

  • Remove the old engine, transmission, and all associated wiring. Label everything you plan to reuse.
  • Clean the engine bay thoroughly. Pressure wash and degrease to spot leaks or rust later.
  • Inspect and replace worn rubber components: motor mount inserts (or fabricate new ones), steering rack bushings, coolant hoses.
  • Test fit the 13B-REW and transmission. You will likely need custom motor mounts — Granny’s Speed Shop offers off-the-shelf kits for popular chassis like the Miata, RX-8, or older RX-7.

If your donor car is a front-engine, rear-wheel-drive platform like an FC RX-7, Miata, or BMW E30, the swap is relatively straightforward. Front-wheel-drive or AWD cars require far more fabrication.

Engine and Transmission Installation

This is where the physical work happens. Patience and proper hoisting are key.

  • Attach your custom engine mounts to the 13B-REW block. Use Grade 8 bolts.
  • Bolt the transmission to the engine. If using the stock RX-7 T56, ensure the bellhousing aligns. For other gearboxes, you may need an adapter plate from IRP or a custom solution.
  • Use an engine hoist to lower the assembly into the bay. Tilting the engine helps clear the firewall and frame rails.
  • Secure mounts to the chassis. Torque to spec (typically 40–60 ft-lbs for mounts).
  • Connect driveshaft, shift linkage, and clutch slave cylinder.

Take your time aligning the drivetrain. A misaligned engine can cause vibrations and premature wear on axles and mounts.

Wiring and ECU Tuning

The 13B-REW uses a complex sequential turbo system and requires careful wiring. The stock ECU is adequate for a stockish build, but for 350 hp you’ll want a standalone.

  • Use the factory harness if it’s intact. Simplify it by removing unnecessary circuits (power windows, audio, etc.) to save weight and clutter.
  • If the harness is cut or missing, buy a pre-built standalone harness from Racing Beat or wire it yourself using a diagram from FSMs available on RX7Club.
  • Choose an engine management system. The F-C Powerhouse offers affordable reflashes of stock ECUs. For full control, consider a Haltech Elite 750 or MicroSquirt — tuneable, widely supported, and capable of handling 350 hp.
  • Wire in the engine management: connect crank and cam sensors, TPS, MAF (or switch to MAP), injectors, ignition coils, and wideband O2.

Professional tuning is recommended for a rotary — they are sensitive to air/fuel ratios and timing. A bad tune can destroy apex seals in minutes.

Fuel and Cooling Systems

Rotaries generate a lot of heat and have specific fuel needs. For 350 hp, these upgrades are non-negotiable:

  • Fuel pump: A Walbro 255 lph in-tank pump is the standard. Hardwire it with a relay to avoid voltage drop.
  • Injectors: Stock 550cc secondary injectors are adequate for 350 hp, but upgrade to 720cc or 1000cc if you plan to run E85 or larger turbos later.
  • Cooling: A high-flow aluminum radiator (Koyo or Mishimoto) is a must. Add an oil cooler — the 13B-REW relies heavily on oil cooling. Use a thermostatic sandwich plate and a quality cooler core.
  • Intercooler: The stock twin turbos benefit from a front-mount intercooler. A 24x12x3 core with 2.5” piping is sufficient for 350 hp.

First Start and Break-In

Before turning the key, triple-check everything:

  • Fill engine with 20W-50 conventional oil (rotary-specific or diesel-rated). Pre-lube by cranking with the fuel pump relay pulled.
  • Fill coolant and bleed the system — air pockets cause rapid overheating in rotaries.
  • Check for fuel leaks at every connection.
  • Start the engine and let it idle at 1,200–1,500 RPM for 10 minutes. Listen for smooth operation and no odd rattles.
  • During the first 500 miles, vary RPM but avoid sustained high load. Break in the apex seals with moderate acceleration and deceleration.

If the engine runs rough, check for vacuum leaks, incorrect timing, or faulty sensors. Rotaries are finicky but rewarding once dialed.

Achieving 350 HP: Modifications and Tuning

Stock 13B-REW engines make around 280 hp at the crank. To reach 350 hp (about 300 whp on most dynos), you need a few targeted upgrades:

  • Boost increase: Stock twins can handle 14–15 psi safely. This alone can add 40–50 hp.
  • Free-flowing intake and exhaust: A cone filter, 3-inch downpipe, and cat-back system reduce backpressure.
  • Fuel system upgrade: Higher flow injectors (720cc secondary) and a fuel pressure regulator.
  • Tuning: A base tune by a rotary specialist on a dyno or with a wideband. Target 11.5:1 AFR under boost and 14.7:1 at cruise.
  • Ignition: Replace spark plugs with NGK BR7EV or BUR9EQ, and use a quality coil upgrade pack (e.g., Scott Performance Coils).

These mods are budget-friendly and keep the total build under $3,000 if you buy used parts. Skip porting the engine — it’s expensive and unnecessary for 350 hp.

Maintenance and Reliability

Rotary engines require more frequent care than piston engines. Plan for:

  • Oil changes every 3,000 miles with high-quality 20W-50 or rotary-specific oil.
  • Premix fuel (1 oz per gallon of 2-stroke oil) to lubricate apex seals, especially if you delete the OMP.
  • Check spark plugs every oil change — rotaries foul plugs easily with rich tuning.
  • Monitor coolant and oil temps — install gauges. Over 220°F coolant or 250°F oil is dangerous.
  • Rebuild at 80,000–100,000 miles as a general rule, though a well-maintained engine can last longer.

Reliability at 350 hp is good if the tune is conservative and cooling is adequate. Many street-driven 13B-REWs run for years without issues.

Conclusion

Installing a 13B-REW swap for under $3,000 and 350 hp is a demanding but achievable project. It requires mechanical skill, patience in sourcing parts, and a willingness to learn rotary-specific quirks. The payoff is a uniquely thrilling engine that revs to the moon and turns heads. Whether you put it in an old RX-7, a Miata, or a lightweight sports car, the 13B-REW swap delivers smiles per dollar that few other builds can match.