Understanding the Cosworth Intake System

The RB20DET engine in the Nissan Skyline R32 responds exceptionally well to improved airflow. Cosworth, a name synonymous with high-performance engine components, has engineered an intake system specifically for this motor. The system replaces the restrictive factory intake manifold with a larger plenum, straighter runners, and a smoother internal surface. This reduces airflow resistance and allows the engine to breathe more freely, resulting in a documented gain of up to 20 horsepower at the wheels when paired with a supporting tune. Beyond the power increase, the improved airflow can enhance throttle response and push the torque curve higher in the rev range, making the R32 more engaging to drive.

The Cosworth intake kit includes the manifold, gaskets, and necessary hardware. Some kits may also include adapter hoses for the idle air control valve and other vacuum lines. Before beginning the installation, verify that the kit is complete and matches your Skyline R32’s specific model year and engine version. Always refer to the Cosworth installation manual for torque values and specific fitment notes.

Tools and Materials Needed

Gathering the correct tools before you start will save time and prevent unnecessary interruptions. Below is the complete list of items you will need.

  • Cosworth intake manifold kit (with gaskets and hardware)
  • Metric socket set (8mm, 10mm, 12mm, 14mm, 17mm)
  • Combination wrenches (10mm, 12mm, 14mm)
  • Phillips and flathead screwdrivers
  • Torque wrench (capable of ft-lbs and in-lbs)
  • Pry bar or trim removal tool (for hose clips)
  • Shop towels or lint-free rags
  • Engine degreaser or brake cleaner
  • Thread-locking compound (medium strength, e.g., Loctite 242)
  • Dielectric grease (for sensor connectors)
  • Vacuum hose replacements (if original hoses are brittle)
  • Antiseize lubricant (for fasteners exposed to heat)
  • Safety glasses and mechanic gloves
  • Fire extinguisher (rated for Class B and C)

Safety Precautions

Working on an engine bay involves flammable fluids, hot surfaces, and electrical hazards. Park the car on a level surface with the engine completely cool. Disconnect the battery negative terminal and wait at least five minutes before proceeding. Keep a fire extinguisher nearby and ensure adequate ventilation if you work indoors. Never work on a hot engine; components can cause burns and gaskets may not seal properly against hot metal. Use jack stands if you need to access the underside of the intake—never rely on a hydraulic jack alone.

Step 1: Preparation and Battery Disconnect

Begin by opening the hood and securing it. Use a memory saver if you wish to preserve radio presets and ECU adaptations, though disconnecting the battery will reset the ECU and allow it to learn the new intake characteristics more quickly. Loosen the negative terminal bolt with a 10mm wrench and slide the cable off. Tuck it away from the battery so it cannot accidentally touch the terminal.

Drain the Coolant (If Necessary)

Some R32 intake manifolds have coolant passages for the throttle body heater. The Cosworth manifold may or may not include these passages depending on version. Check the instructions. If coolant lines are connected, drain the radiator coolant into a clean container before disconnecting hoses. Use a drain pan under the radiator petcock and open it slowly. This step prevents coolant from spilling onto wiring and the alternator.

Step 2: Removing the Factory Intake System

Remove the air filter box, intake pipe, and air flow meter assembly to gain access to the intake manifold. Label the hoses and electrical connectors with tape or a marker. Take reference photos with your phone—this will be invaluable during reassembly.

Disconnect Vacuum Lines and Sensors

The RB20DET intake manifold has several vacuum lines: fuel pressure regulator, blow‑off valve, boost controller, brake booster, and the idle air control valve. Carefully disconnect each one. Remove the throttle cable from the bracket and throttle linkage. Unplug the engine coolant temperature sensor and knock sensor connectors that may be attached to the manifold. Use dielectric grease on the connectors before reinstalling.

Unbolt the Intake Manifold

Using a 12mm socket, remove the manifold mounting bolts. There are typically 10–12 bolts and a few nuts on studs. Work from the outside inward to avoid warping the manifold. Keep the old gaskets; you can compare them to the new Cosworth gaskets for correct orientation. Lift the manifold off the engine. Be careful not to damage the intake valves or drop debris into the ports—stuff a clean rag into the intake openings on the cylinder head.

Step 3: Engine Bay Cleaning and Inspection

With the intake removed, use engine degreaser and shop towels to clean the engine block deck, the area around the intake ports, and any surfaces where the new gasket will sit. Remove any old gasket material with a plastic scraper—do not use a metal scraper that can scratch the aluminum or steel. Blow out the bolt holes with compressed air to ensure no standing cleaner or debris remains. Inspect the intake ports for carbon buildup; if heavy deposits are present, consider a walnut blasting service before installing the new manifold.

Check the Throttle Body and IACV

Now is a good time to clean the throttle body and idle air control valve (IACV). Use a dedicated throttle body cleaner and a soft brush. Replace the throttle body gasket if it shows signs of wear. Ensure the IACV passageways are clear to prevent erratic idle after installation.

Step 4: Installing the Cosworth Intake Manifold

Prepare the new Cosworth manifold. Verify that the intake runner outlets are free of packaging debris. Place the new gaskets onto the cylinder head studs or locate them with dowel pins if provided. Some Cosworth kits use a silicone gasket that must be positioned carefully—do not use additional sealant unless instructed.

Position the Manifold

Lower the manifold onto the engine. Align all runners with the gaskets simultaneously. Do not force it; if it does not seat easily, check for misaligned gaskets or obstructions. Once seated, hand‑tighten all bolts and nuts in a crisscross pattern starting from the center. This ensures even compression of the gaskets.

Torque to Specification

Using a torque wrench, tighten the manifold fasteners to the specification provided by Cosworth. Typically this is around 14–18 ft‑lb for the main bolts and 6–10 ft‑lb for smaller stud nuts. Follow the tightening sequence in the Cosworth manual (usually center outward). Apply a drop of thread‑locking compound to bolts that are not on studs to prevent loosening from vibration.

Step 5: Reconnecting Ancillaries and Sensors

Reattach the throttle body to the new manifold using a new gasket. Torque the throttle body bolts to factory spec (approximately 7–9 ft‑lb). Reconnect all vacuum lines according to your reference photos. The Cosworth manifold may have relocated vacuum ports; some lines may need extended hoses. Use quality silicone vacuum hose to replace any short sections.

Reattach Electrical Connectors

Plug in the coolant temperature sensor, knock sensor, idle air control valve connector, throttle position sensor, and any other sensors that were disconnected. Apply dielectric grease to the terminals for corrosion protection. Route wiring harnesses away from hot surfaces and sharp edges.

Reconnect the Coolant Hoses

If your Cosworth manifold incorporates coolant passages, reconnect the two small coolant hoses to the throttle body. Use new clamps. Refill the coolant system with the proper Nissan blue or green ethylene glycol coolant mixed 50/50 with distilled water. Bleed the cooling system per the R32 service manual.

Step 6: Final Checks and Startup

Before reconnecting the battery, double‑check that all bolts are torqued, all connectors are seated, and no tools or rags remain in the engine bay. Reconnect the negative battery terminal and tighten it securely. Turn the ignition key to the ON position but do not start the engine. Listen for the fuel pump prime—check for any fuel leaks around the fuel pressure regulator vacuum line.

Start the Engine

Start the engine and let it idle. The idle may be high initially as the ECU re‑learns. Check for vacuum leaks by listening for hissing sounds. Spray a small amount of brake cleaner around gasket mating surfaces; a noticeable increase in engine speed indicates a leak. Turn off the engine and tighten any suspect connections. Restart and allow the engine to reach operating temperature while monitoring coolant temperature and oil pressure gauges.

Check for Codes

Use an OBD‑I scanner (or a simple LED diagnostic procedure) to check for error codes. Common codes after an intake swap are related to the idle air control or coolant temperature sensor—these usually resolve after a drive cycle. Clear any codes that appear after verifying the sensors are connected correctly.

Post‑Installation Tuning and Performance Validation

Installing the Cosworth intake increases airflow significantly. The standard R32 ECU will provide some adaptation, but to realize the full 20‑horsepower gain and prevent lean fuel mixtures, a custom ECU tune is strongly recommended. A dyno tune by an RB specialist will optimize the fuel and ignition maps for the new intake volume and flow characteristics. Even without a tune, you may notice improved throttle response, but the horsepower gain will be modest (around 8–12 HP) until recalibrated.

Break-In Procedure

Drive the car gently for the first 100 miles. Avoid sustained wide‑open throttle runs until the gaskets have fully compressed and settled. Vary the engine speed to help the ECU learn the new airflow patterns. After 100 miles, re‑torque the intake manifold bolts (cold) to ensure they have not loosened. Check all vacuum lines and hose clamps for tightness.

Common Mistakes and How to Avoid Them

  • Forgetting to re‑torque bolts after heat cycling: Metal expansion and gasket compression can loosen fasteners. Always perform a hot retorque after the first drive.
  • Using incorrect thread locker: Avoid high‑strength thread locker on intake bolts, as disassembly later may be difficult. Medium‑strength (blue) is ideal.
  • Overtightening the manifold: This distorts the runners and causes air leaks. Use a torque wrench every time.
  • Neglecting the throttle body gasket: A worn gasket here can cause a massive vacuum leak. Replace it as part of the job.
  • Failing to reset the ECU: Even if the battery was disconnected, after startup the ECU needs a reset procedure (drive cycle) to fully adapt. Some tuners recommend an ECU reset via disconnecting the battery for 30 minutes after the first start.

External Resources and Further Reading

For additional technical specifications and community advice, refer to these trusted sources:

Conclusion

Installing a Cosworth intake manifold on your Nissan Skyline R32 is a rewarding project that delivers tangible performance gains. By following the detailed steps in this guide—from proper cleaning and gasket preparation to torque sequences and post‑installation tuning—you can ensure a reliable, leak‑free installation. The improved airflow not only adds horsepower but also sharpens the engine’s character, making your R32 even more exhilarating to drive. Regular maintenance, such as checking gaskets and cleaning the throttle body every 20,000 miles, will preserve the benefits for years to come. If you are new to engine work, consider having an experienced mechanic supervise your first attempt. The result—a Skyline that breathes like a true performance machine—is well worth the effort.