Guide To Swapping A Mazda 13b Rotary Engine Into A Nissan 240sx

The allure of the Mazda 13B rotary engine is undeniable. Its compact size, high-revving nature, and distinct sound make it a desirable powerplant for enthusiasts seeking something different. Combining this engine with the lightweight and readily available Nissan 240SX (S13 or S14 chassis) presents a tempting proposition. However, this swap is far from a bolt-in affair. It demands careful planning, meticulous execution, and a thorough understanding of both the engine and the chassis. This guide will walk you through the key considerations and technical challenges involved in this complex but rewarding swap.

Planning and Preparation: Laying the Groundwork

Before even turning a wrench, planning is paramount. A successful 13B swap hinges on diligent research and acquisition of the necessary components. Start by defining your goals. Are you aiming for a reliable street car, a track weapon, or something in between? This will influence your engine choice, fuel system requirements, and other crucial decisions.

Engine Selection: Which 13B is Right for You?

Numerous 13B variants exist, each with its strengths and weaknesses. Common options include:

13B-REW (FD RX-7): The most powerful stock 13B, featuring sequential twin turbos. Complex and potentially problematic due to its age and intricate plumbing. Expect to rebuild or replace the turbos.
13B-RE (JDM Cosmo): Similar to the REW but with a single, larger turbo. Potentially more reliable and simpler to tune.
13B (NA): Naturally aspirated versions found in various RX-7 models. Simpler and generally more reliable than turbocharged variants, but with significantly less power. A good option for budget builds or those prioritizing responsiveness over outright horsepower.
13B-MSP Renesis (RX-8): While modern, the Renesis presents unique challenges. Its side-port design and auxiliary ports require careful management. It also suffers from oiling issues and lower power potential than earlier 13Bs without significant modifications.

Regardless of your choice, factor in the engine's condition. A complete rebuild is highly recommended, especially for older engines. This allows you to inspect and replace worn components, ensuring reliability and longevity. Consider upgrading to stronger apex seals, a common failure point in rotary engines, particularly under boosted conditions.

Essential Components and Considerations

Beyond the engine itself, you'll need a variety of parts specifically designed for this swap:

Mounting Kit: Aftermarket kits provide engine and transmission mounts compatible with the 240SX chassis. These kits simplify installation and ensure proper engine alignment.
Transmission Adapter: The 13B doesn't directly bolt to the 240SX transmission. An adapter plate is required. Consider using a stronger transmission than the stock 240SX unit, such as a Toyota R154 or CD009, as the rotary's high-revving nature can quickly overwhelm the factory gearbox.
Driveshaft: A custom driveshaft will be necessary to connect the transmission to the rear differential. Ensure it's properly balanced and rated for the intended power level.
Fuel System: The stock 240SX fuel system is unlikely to be adequate, especially for turbocharged 13Bs. Upgrade the fuel pump, injectors, and fuel lines to handle the increased fuel demands. A fuel pressure regulator is also crucial for maintaining consistent fuel pressure.
Cooling System: The 13B generates significant heat. A larger radiator, upgraded fans, and proper ducting are essential to prevent overheating. Ensure the radiator cap is rated for the correct pressure.
Exhaust System: Fabricating a custom exhaust system is almost unavoidable. Consider the placement of the turbocharger (if applicable) and the desired exhaust note. A properly designed exhaust system can significantly improve performance.
Wiring Harness: Integrating the 13B's wiring harness into the 240SX chassis is one of the most challenging aspects of the swap. You can either modify the existing harnesses or opt for a standalone engine management system (EMS).
Engine Management System (EMS): A standalone EMS provides precise control over fuel, ignition, and other engine parameters. This is highly recommended for turbocharged engines and allows for custom tuning to maximize performance and reliability. Common choices include Haltech, AEM, and Megasquirt.
Sensors and Gauges: Monitor vital engine parameters such as oil pressure, coolant temperature, and air/fuel ratio. Aftermarket gauges provide real-time feedback and can alert you to potential problems before they become catastrophic.

The Swap Process: A Step-by-Step Overview

Once you've gathered all the necessary components, the real work begins. This is a complex project that requires mechanical aptitude, welding skills, and a thorough understanding of automotive systems.

Engine and Transmission Installation

Remove the existing engine and transmission from the 240SX. Thoroughly clean the engine bay.
Install the engine and transmission mounts. Ensure they are properly aligned and securely fastened.
Lower the 13B and transmission into the engine bay. Take your time and carefully maneuver the engine to avoid damaging any components.
Connect the transmission to the engine using the adapter plate. Verify proper alignment and torque the bolts to the manufacturer's specifications.
Install the driveshaft. Ensure it's properly balanced and connected to the transmission and rear differential.

Fuel System Installation

Install the upgraded fuel pump. Ensure it's properly wired and grounded.
Install the fuel injectors. Replace the fuel lines and fittings with those compatible with the new injectors.
Connect the fuel pressure regulator. Adjust the fuel pressure to the manufacturer's specifications.
Test the fuel system for leaks. Use a fuel pressure gauge to verify proper operation.

Cooling System Installation

Install the larger radiator. Ensure it's properly mounted and connected to the engine.
Install the upgraded fans. Wire the fans to operate at the correct temperature.
Connect the coolant hoses. Use high-quality hoses that are resistant to heat and pressure.
Fill the cooling system with coolant. Bleed the system to remove any air pockets.

Exhaust System Fabrication

Plan the exhaust routing. Consider the placement of the turbocharger (if applicable) and the desired exhaust note.
Fabricate the exhaust system using mandrel-bent tubing. Ensure all welds are strong and leak-free.
Install the exhaust system. Use proper hangers to support the exhaust system and prevent it from rattling.

Wiring and EMS Installation

Identify the necessary wires from the 13B wiring harness. This includes power, ground, ignition, fuel injection, and sensor signals.
Integrate the 13B wiring harness into the 240SX chassis. This may involve splicing wires, adding connectors, and rerouting cables.
Install the standalone EMS. Connect the EMS to the engine sensors and actuators.
Configure the EMS software. This involves setting up the fuel and ignition maps, as well as configuring the sensor inputs and outputs.

Tuning and Troubleshooting: Fine-Tuning Your Rotary Swap

Once the swap is complete, tuning is crucial for achieving optimal performance and reliability. This typically involves dyno tuning by a qualified professional experienced with rotary engines and standalone EMS systems.

Common issues that may arise during tuning include:

Apex Seal Failure: As mentioned earlier, apex seals are a weak point in rotary engines. Detonation or improper tuning can lead to premature failure.
Oiling Issues: Rotary engines require a constant supply of oil to lubricate the rotors and housings. Insufficient oil pressure or improper oil metering can lead to engine damage.
Overheating: Rotary engines generate significant heat. An inadequate cooling system can lead to overheating, which can damage the engine.
Fueling Problems: Inadequate fuel supply or improper fuel pressure can lead to lean conditions, which can damage the engine.
Ignition Problems: Weak or misfiring ignition can lead to poor performance and engine damage.

Thoroughly inspect all components after each tuning session and address any issues promptly. Regular maintenance, including oil changes and spark plug replacements, is essential for maintaining the longevity of your rotary-powered 240SX.

The 13B rotary swap into a 240SX is a challenging but rewarding project. With careful planning, meticulous execution, and a thorough understanding of both the engine and the chassis, you can create a unique and exciting machine that stands out from the crowd.

Conclusion

This guide provides a comprehensive overview of the Mazda 13B rotary engine swap into a Nissan 240SX. While it covers the major aspects, it is crucial to remember that each build is unique and may require variations to the process. Research extensively, consult with experienced builders, and take your time. The result, a screaming rotary in a nimble chassis, is well worth the effort.