Understanding the 13B-REW Engine

The Mazda 13B-REW is a twin-rotor rotary engine that powered the third-generation Mazda RX-7 (FD3S) from 1992 to 2002. It features sequential twin-turbocharging, an advanced fuel injection system, and a lightweight aluminum housing that makes it a favorite for engine swaps. The engine produces approximately 255–280 horsepower in stock form, with peak torque of about 217–250 lb-ft. The 13B-REW is known for its high-revving nature and compact dimensions, enabling it to fit into many lightweight platforms, such as the Mazda MX-5 Miata, older RX-7s (FB/FC), and even kit cars like the Factory Five GTM.

Before proceeding, understand the engine’s key specifications:

  • Displacement: 1,308 cc (1.3L) per two rotors
  • Configuration: Twin-rotor, twin-turbo (primary and secondary turbos)
  • Injector setup: Primary 550 cc/min, secondary 850 cc/min
  • Compression ratio: 9.0:1
  • Dry weight: Approximately 280 lbs (127 kg)
  • Redline: 8,000 RPM (stock ECU)

Because rotary engines generate power differently than piston engines, they require specific cooling and oiling considerations. The 13B-REW also has a unique exhaust port design that can produce a linear torque curve if the sequential turbo system is properly maintained or replaced with a single-turbo conversion. For a swap, you will likely encounter three engine variants: the JDM (Japanese Domestic Market) version with 280 hp limit, the USDM version with slightly lower output, and remanufactured units. Source your engine from a reputable supplier; check Rotary Aviation or RX7Club for trusted sellers.

Total Cost Breakdown for a 13B-REW Swap

Budgeting for a 13B-REW swap requires planning across multiple categories. Prices vary by region, condition of parts, and whether you perform labor yourself. Below is a detailed estimate for a complete swap including the engine, transmission, cooling, fueling, and electronics. All prices are in USD and assume a clean donor or reman engine.

  • Engine Core (used, complete with turbos): $2,500 – $5,500
  • Remanufactured 13B-REW: $4,000 – $7,000
  • Transmission (stock FD or custom): $1,000 – $2,500
  • Engine and transmission mounts: $200 – $600
  • Wiring harness (standalone or modified stock): $300 – $1,500
  • ECU (Megasquirt, Haltech, PowerFC, etc.): $700 – $2,000
  • Radiator and oil cooler: $400 – $1,200
  • Fuel system (pump, lines, regulator): $300 – $800
  • Exhaust system (downpipe, midpipe, muffler): $400 – $1,200
  • Intercooler and piping: $200 – $600
  • Misc (gaskets, seals, fluids, hardware): $300 – $800
  • Labor (if not DIY): $1,000 – $3,000
  • Tuning and dyno time: $400 – $1,000

Total estimated range: $7,000 – $17,000 depending on condition and upgrades. A budget build using a used engine, stock ECU with reflash, and reused transmission might cost under $8,000, while a high-end build with a rebuilt engine, six-speed transmission, and standalone ECU could exceed $18,000. Always allocate an additional 10–15% for unplanned expenses like custom driveshafts or unexpected corrosion.

Preparation: Tools and Workspace

Before lifting the hood, gather the essential tools. This swap requires at least a weekend of solid work for a skilled enthusiast, but first-timers should plan for two to three weekends. You will need:

  • Engine hoist (2-ton capacity)
  • Engine leveler
  • Socket set (metric, 8–24 mm)
  • Wrenches and ratcheting wrenches
  • Impact wrench
  • Torque wrench (ft-lb and in-lb)
  • Jack stands (4) and a floor jack
  • Pickle fork and ball joint separator
  • OBD or rotary-specific diagnostic tool
  • Multimeter and soldering iron (for wiring)
  • Safety glasses, gloves, and fire extinguisher

Clean your workspace, have adequate lighting, and store parts in labeled bins. If possible, lift the vehicle onto four stands to allow access underneath. Read the factory service manual for both the donor car and your chassis; many resources are available on RTFM or community forums.

Step-by-Step Installation Guide

Step 1: Remove the Original Engine and Transmission

Disconnect the battery and drain all fluids (coolant, oil, transmission fluid). Remove the hood for better access. Disconnect the intake, exhaust, and all electrical connectors. Label connectors with tape if using the original harness. Remove the radiator and fan assembly. Unbolt the transmission from the engine and support it with a jack. Use your engine hoist to lift the old engine out carefully. Check for any obstructions like hidden bolts or hoses.

Step 2: Prepare the 13B-REW Engine

Inspect the engine thoroughly. If bought used, do a compression test (ideal: above 100 psi per face, 84–100 psi acceptable). Replace the front main seal, oil pan gasket, and apex seals if unknown condition. Install new spark plugs (NGK BUR9EQP recommended). Attach engine mounts—these will depend on your chassis. For a Miata swap, use adapters from IR Performance or fab your own. For an FC RX-7, the 13B-REW can bolt to stock mounts with minor modification. Pre-fit the turbo system or decide on a single-turbo conversion now to save access later.

Step 3: Install the Engine and Transmission

Attach the transmission (typically a 5-speed from an FC or a 6-speed from an FD) to the engine before dropping it in. Use a pilot bearing specific to the combination. Grease the clutch disc splines. Using the hoist and leveler, lower the assembly into the engine bay. Align the mounts to the chassis; it may be necessary to adjust the transmission crossmember. Bolt the engine and transmission firmly. Reinstall the radiator, intercooler, and all cooling hoses. The 13B-REW runs hot, so upgrade to a high-flow radiator (e.g., Koyo or Mishimoto) and a thermostatic oil cooler.

Step 4: Wiring and ECU Installation

This step is the most complex. You have two paths: reuse the stock FD ECU and harness (requires integrating with donor chassis) or install a standalone ECU. Standalone options like Haltech Elite 2500 or AEM Infinity allow custom tuning and delete unused systems. If you choose standalone, remove all unneeded wiring (secondary air, EGR, etc.). Modify the stock harness if you are comfortable: cut connectors, repin for the new chassis, and add fuses. Always use relayed power for fuel pumps and ignition. Protect all wiring with loom and zip ties. If you get stuck, consider a plug-and-play harness from companies like Wireworx.

Step 5: Fuel and Cooling Systems

Remove the old fuel tank or prepare an in-tank pump. The 13B-REW demands high flow; use a Walbro 255 lph or larger pump. Replace fuel lines with -6AN or larger to handle pressure. Install an adjustable fuel pressure regulator (set to 43 psi base for injectors). For cooling, upgrade to a high-capacity radiator with dual electric fans. The rotary engine’s rotor housings need consistent coolant flow; ensure you route the upper and lower radiator hoses correctly. Add an oil cooler with a thermostat—mount it in front of the radiator. Also, consider an aluminum radiator shroud for proper airflow.

Step 6: Exhaust and Drivetrain

Test-fit the downpipe. The 13B-REW’s turbo outlets are close to the firewall in many swaps; a custom downpipe may be needed. Use a flexible exhaust section to reduce stress. For the driveshaft, have it shortened or custom-made to match the new transmission tail and differential flange. If your donor car has a weaker differential, upgrade to a Torsen or clutch-type limited-slip unit from the FD or Miata. Check axle splines and output flanges. Bleed the clutch hydraulic system and adjust the pedal travel.

Step 7: Final Checks and Startup

Double-check all bolts: engine mounts, transmission crossmember, turbo nuts, and wiring grounds. Fill engine oil (synthetic 5W-40 or 10W-40 with rotary-specific additive). Fill coolant with a 50/50 mix and bleed the system. Reconnect the battery and turn the key to prime the fuel pump. Inspect for fuel leaks. For the first start, disable spark/fuel initially to build oil pressure by cranking for 10 seconds a few times. Then reinstall spark plugs and fuel injector connectors. Start the engine and listen for unusual noises. Allow the engine to idle and warm to normal temperature. Check for oil pressure on the gauge. If using a standalone ECU, load a base map from the manufacturer or tuner. Perform a short test drive, then return for spark plug inspection and to re-torque header bolts.

Common Challenges and Troubleshooting Tips

  • Overheating: The 13B-REW swaps often run hot due to inadequate radiator airflow. Solution: Use a larger radiator, high-flow thermostat (170°F), and electric fan with proper shrouding.
  • Wiring gremlins: Mismatched connectors and accidental shorts. Tip: Label all wires, use a multimeter for continuity checks, and consider a dedicated fuse box for new circuits.
  • Turbo lag: The sequential system is complex. Many swappers convert to a single turbo for simplicity and quicker spool. Plan this before installation.
  • Transmission alignment: If the bellhousing does not sit flush, the pilot bearing may be wrong. Always measure the input shaft length and pilot bearing diameter.
  • Tuning difficulty: Rotary engines have a narrow tuning window for air/fuel ratio (12.2:1 at WOT). Seek a professional tuner with rotary experience; see recommendations on RX8Club.

Conclusion

A 13B-REW swap is an achievable project for a dedicated enthusiast with basic mechanical skills. The key to success lies in thorough preparation, a realistic budget, and patience with the wiring and cooling systems. By following this expanded guide, you can transform your chassis into a lightweight, high-revving rotary machine. Always prioritize safety, use torque specifications, and consult community resources like the RX7Club forums when challenges arise. With careful planning, the sound and performance of a 13B-REW swap will reward you every time you press the starter.