Introduction to the Garrett T04 Upgrade for the 3000GT VR4

The Mitsubishi 3000GT VR4 (and its twin, the Dodge Stealth RT/TT) is a legend among 1990s Japanese turbos. Its factory twin-turbo 6G72 engine delivers impressive power from the factory, but enthusiasts quickly find the stock TD04 turbos fall short on top-end flow and reliability when pushing higher boost. Swapping to a single, larger turbo like the Garrett T04 series is a well-trodden path to unlock serious horsepower. The T04 frame offers a broad range of compressor trims and turbine housings, letting you tailor the powerband to your goals—whether you want a fast street car or a track monster.

This guide expands on the basic steps required to install a Garrett T04 turbocharger on a 3000GT VR4. Beyond simply bolting on parts, we’ll cover critical considerations like oil system modifications, wastegate plumbing, intercooler routing, and initial tuning. The goal is a reliable installation that performs consistently. Before you begin, gather your tools, clear your schedule for a full weekend, and have a factory service manual or wiring diagram handy. We also recommend reading the latest discussions on 3SI.org for platform-specific tips.

Tools, Materials, and Preparation

Required Tools and Hardware

  • Garrett T04 turbocharger – choose a trim that matches your power targets. Popular options include the T04E 60-trim for quick spool or the T04B for a broader range. Ensure the turbine housing is flanged for your chosen manifold (T3, T4, or custom).
  • Turbo manifold – a cast or tubular T4 or T3 manifold designed for the 3000GT VR4. Many aftermarket options are available (e.g., from AMS, PAMP, or custom fabricators).
  • Wastegate – external wastegate is mandatory with a single turbo. Choose a 38mm to 50mm unit. Make sure it includes a spring rated for your boost target (e.g., 7 psi spring for base pressure). Vacuum lines and routing hardware also needed.
  • Oil feed and return lines – the T04 requires a constant supply of clean oil. Use a -3AN or -4AN braided stainless feed line with a restrictor if necessary. The return line should be -10AN or -12AN to prevent oil backup. Check your turbo’s bearing type: journal bearings need more oil flow than ball bearings.
  • Intercooler and piping – front-mount intercooler (FMIC) with core dimensions around 24x12x3 inches. Silicone couplers in appropriate sizes (2.5”, 3”, etc.) and T-bolt clamps. Cold-side and hot-side piping to match the compressor outlet and throttle body.
  • Gaskets and sealants – manifold-to-head gasket, turbo-to-manifold gasket, wastegate flange gasket, and copper spray or high-temp RTV for connections.
  • Fasteners – new grade 8 bolts for the manifold, locking nuts, and flat washers. Torque wrench (ft-lb and in-lb), socket set, wrenches, pry bar, and a tap/die set for cleaning threads.
  • Boost gauge and electronic accessories – quality mechanical or electronic boost gauge (e.g., AEM, Autometer). A boost controller can be added later but at least have a gauge.
  • Fuel management system – strongly recommended. Options include an ECU flash (e.g., ECUTek, AEM EMS), piggyback (SAFC), or standalone. Large injectors (850cc+) and a high-flow fuel pump (Walbro 450) are also required.

Pre-Installation Steps

Park the car on a level concrete surface and chock the wheels. Disconnect the battery negative terminal. Remove the engine undercover and drain the coolant and oil if you plan to service them. It’s a good time to change the oil and filter after the install. Remove the heat shields, intake piping, and intercooler plumbing to gain access. Label all connectors and hoses. Take photos of the original twin-turbo configuration—it's your reference if something goes wrong.

Inspect the engine bay for any oil leaks, worn vacuum hoses, or corroded fasteners. Replace them now to avoid chasing issues later. If your VR4 has high mileage, consider replacing the valve cover gaskets, spark plugs, and ignition coils while the area is accessible. Also, verify that your cooling system is in good shape—a single turbo can generate more heat than the twins.

Removing the Factory Twin-Turbo System

Step 1: Remove intake and exhaust components

Unbolt the air filter box and intake ducting. Disconnect the mass airflow sensor (MAF) and set it aside. Remove the intercooler piping and the two side-mount intercoolers (or aftermarket FMIC if previously installed). Label each section to avoid confusion during reinstallation.

Next, loosen the front exhaust downpipes from the turbo outlets. The two turbos are located forward of the engine, below the exhaust manifolds. You’ll need to access the bolts from underneath using a long extension and universal joint.

Step 2: Disconnect oil and coolant lines

Each factory turbo has oil feed lines from the engine block and oil return lines to the oil pan. Coolant lines also run through the turbo bearings. Clamp off the coolant hoses to minimize spillage. Remove the lines carefully—they are often seized. Use penetrating oil and gentle heat if needed. Plug all open ports on the engine to prevent dirt ingress.

Step 3: Unbolt the turbos

With everything disconnected, support each turbo from below and remove the manifold-to-turbo bolts. The casting is heavy; lift it straight out. Repeat for the second turbo. Inspect the exhaust manifold gaskets for damage. Clean the cylinder head mating surfaces with a plastic scraper and brake cleaner. Do not scratch the aluminum.

At this point, you can also remove the twin turbo heat shields and any brackets that are no longer needed. This is a good moment to install a blocked-off oil return port fitting if you plan to reuse the stock oil pan or drill and tap a new -10AN fitting for the single turbo return line.

Installing the Garrett T04 Turbocharger

Step 1: Mount the manifold

Apply a thin layer of copper anti-seize to the exhaust studs. Install the new single turbo manifold using new gaskets. Torque the nuts in a crisscross pattern to the factory specification (typically 15-20 ft-lb). Do not overtighten, as the manifold may warp. If using a tubular manifold, support it with a bracket to reduce thermal stress.

Step 2: Prepare the Garrett T04

Check the turbo for free rotation by spinning the compressor wheel. Apply a few drops of oil to the center bearing housing inlet before installation. If your turbo has ball bearings, ensure the oil restrictor is in place—most Garrett ball-bearing units require a 0.035” – 0.060” restrictor. For journal bearings, use a -4AN feed line without a restrictor unless the manufacturer specifies otherwise.

Step 3: Bolt the turbo to the manifold

Use the supplied T4 or T3 gasket between the manifold and turbo flanges. Apply a light coat of high-temp copper sealant on both sides. Tighten the bolts in sequence to 25-30 ft-lb (check the turbo manual). Mount the wastegate to the flange on the turbo or manifold using the included hardware. The wastegate dump tube should be routed back into the exhaust downpipe, or you can run it open (but be prepared for extra noise).

Step 4: Connect oil lines

Run the oil feed line from an oil pressure source (usually the oil filter housing or a dedicated port) to the turbo. Use a -3AN or -4AN stainless braided hose. Secure the line away from hot surfaces with heat wrap or silicone sleeves. The oil return line must have a large inner diameter (min -10AN) and a gentle slope back to the oil pan. If you drilled the pan, use a weld-on -10AN bung and ensure it is above the oil level. Connect the return line with a silicone 45° or 90° hose to prevent kinking.

Step 5: Coolant lines (optional)

Some T04 turbos are water-cooled. If yours has coolant ports, connect them to the engine’s cooling system using -6AN lines. You can use a tee from the heater core hose or a plugged port near the thermostat. Water cooling helps reduce coking after shutdown. If you don’t use coolant lines, ensure the turbo has adequate oil cooling (ball-bearing turbos can run oil-only).

Intercooler and Piping Installation

Step 1: Mount the front-mount intercooler

Remove the front bumper support trim and crash bar (or relocate it). Test-fit the FMIC core, then fabricate brackets or use universal mounting kits. Ensure the core sits at least 1 inch away from the radiator for airflow. Trim the plastic shroud as needed. Many VR4 owners choose a core with a 3” inlet/outlet and 2.5” end tanks.

Step 2: Build the hot and cold side piping

Using silicone couplers and aluminum tubing (2.5” or 3” diameter), connect the turbo compressor outlet to the intercooler inlet (hot side). Then from the intercooler outlet to the throttle body (cold side). Keep the piping as short and smooth as possible to minimize lag. Use a bypass valve (BOV) on the cold side near the throttle body. Route the BOV recirculation hose back into the intake after the MAF, or vent to atmosphere if you use a speed-density tune.

Secure all couplers with T-bolt clamps torqued to 30-35 in-lb. Test for leaks before the final start by pressurizing the system to 15-20 psi with a boost leak tester (available at Garrett Motion).

Finalizing the Installation

Electrical and sensor connections

Reinstall the MAF sensor (or adapt the intake pipe for a blow-through MAF). If you are using a standalone ECU, remove the MAF and install a MAP sensor and IAT sensor in the intercooler piping. Connect a boost gauge reference line to the intake manifold. Install an electronic boost controller solenoid if desired.

Reinstall components and refill fluids

Replace the battery, reconnect the ground. Fill the engine with new oil and filter. Refill coolant, making sure to bleed air from the system (use the bleed screw on the thermostat housing). Check all hoses, especially the brake booster vacuum line and clutch master cylinder, which may be in the way.

Leak and pressure checks

Before starting the engine, perform a boost leak test on the intercooler piping and intake system. Then, prime the turbo by disabling the fuel pump (pull the fuel pump relay) and cranking the engine for 10 seconds. This will circulate oil without combustion. Reconnect the fuel pump relay.

Start the engine and let it idle. Listen for exhaust leaks at the manifold and wastegate flanges. Check for oil leaks around the feed and return lines. Let the engine reach operating temperature, then shut it off and recheck the coolant level. Ensure the radiator fan cycles on and off.

Testing and Initial Tuning

With the engine idling smoothly, verify the boost gauge reads vacuum (around -20 inHg at idle). Take the car for a very gentle first drive, keeping the boost below 5 psi until you have confirmed everything is secure. After a short run, re-torque the manifold nuts once they cool down.

A single turbo conversion drastically changes the engine’s air/fuel ratios. Do not drive aggressively until the car is properly tuned. Use a wideband O2 sensor (e.g., AEM UEGO) to monitor the mixture. Target 11.5:1 at full boost to be safe. If you are using a piggyback or stock ECU with a tune, install larger injectors (750–1000cc) and adjust the fuel map accordingly. Many shops offer remote tuning for the 3000GT VR4; consider contacting specialists at AMS Performance for a custom calibration.

If you encounter boost creep, check the wastegate spring rate and ensure the exhaust flow is not restricted. A blown wastegate gasket can cause erratic boost. Also verify that the boost controller is set to minimum boost for break-in.

Conclusion

Converting your 3000GT VR4 to a single Garrett T04 turbocharger is a major project that rewards you with a broader torque curve, higher peak power, and a more linear power delivery compared to the factory twin-turbo setup. This guide provides the framework for a reliable installation, but remember that every car is unique. Pay attention to oil routing, wastegate placement, and intercooler efficiency. With proper preparation and tuning, your VR4 will be transformed into a beast that can hold its own against modern sports cars.

For further reading and community support, join the discussion at Stealth316.com and the 3SX Performance parts catalog. Happy boosting!