Unlocking the Full Potential of Your 3S-GTE: The HKS 3037A Turbo Installation Guide

The HKS 3037A is a legendary turbocharger upgrade for the 3S-GTE engine, found in iconic vehicles such as the Toyota MR2 SW20, Celica GT-Four (ST205/ST185), and Caldina GT-T. This single-scroll turbo is designed to deliver a potent balance of quick spool and high top-end power, capable of supporting 350–500+ wheel horsepower depending on supporting modifications. Proper installation is critical to achieving reliable performance and avoiding costly mistakes. This guide provides a detailed, step-by-step breakdown of the entire installation process, from tool preparation to final boost testing.

Tools, Materials, and Parts Checklist

Before lifting a wrench, gather all necessary items. Using correct components ensures a smooth installation and prevents boost leaks, oil starvation, or damaged turbocharger.

Required Tools

  • Socket set (metric, 8mm–19mm) with extensions and universal joints
  • Combination wrenches (10mm–22mm)
  • Torque wrench (capable of 10–80 ft-lb)
  • Screwdrivers (flathead and Phillips)
  • Pry bar or crowbar for stubborn exhaust joints
  • Jack and jack stands (or lift)
  • Drain pan for oil and coolant
  • Vacuum/pressure tester for boost leak checking
  • Safety goggles and mechanic gloves

HKS 3037A Kit Components

  • HKS 3037A turbocharger (includes actuator and diaphragm)
  • Cast iron exhaust manifold (often part of full kit)
  • Downpipe adapter or complete downpipe
  • Oil feed and drain lines with banjo bolts and crush washers
  • Coolant feed and return hoses
  • Gaskets (manifold-to-head, turbo-to-manifold, downpipe-to-turbo)
  • Hardware kit (studs, nuts, bolts, washers)

Additional Parts You May Need

  • New OEM or ARP exhaust manifold studs – the factory studs often break during removal
  • Intercooler piping kit (2.5″ or 3″) with silicone couplers and T-bolt clamps
  • Intercooler core (if upgrading from stock top-mount)
  • Blow-off valve (HKS SSQV recommended for sound and reliability)
  • Oil (5W-30 or 10W-40, quality synthetic) and OEM oil filter
  • Coolant (Toyota long-life coolant or equivalent)
  • Boost controller (manual or electronic) and boost gauge
  • Engine management solution (e.g., standalone ECU, piggyback, or reflash) – the 3037A demands retuning

Preparation Steps – Setting the Stage

Begin working on a cool engine. Disconnect the negative battery terminal to prevent accidental short circuits or fuel pump activation. Raise the vehicle securely on jack stands; you need clearance to access the underside of the engine.

Drain the engine oil and coolant into approved containers. Remove the engine undercover and any heat shields blocking the exhaust manifold and turbo area. If you have a top-mount intercooler, remove it along with its bracket to free up space. Label all vacuum lines and electrical connectors before disconnecting them.

Remove Intake and Exhaust Systems

Detach the air intake system from the turbo inlet, including the mass air flow sensor connector and intake tubing. Unbolt the exhaust downpipe from the turbo outlet and the catalytic converter. It is often easier to remove the downpipe completely along with the turbo support bracket.

If you are replacing the exhaust manifold, unbolt it from the cylinder head. Apply penetrating oil to the manifold-to-head nuts several hours in advance. Use a six-point socket and steady pressure to avoid rounding. If a manifold stud breaks, refer to a thread repair kit or consult a machine shop.

Removing the Factory Turbocharger

With the intake and exhaust manifolds free, you can access the turbo. Disconnect the oil feed line from the turbo center housing (usually a banjo bolt). The oil drain line is a large fitting on the bottom; unbolt it from the turbo and the oil pan. Remove the coolant lines: one feed from the engine block and one return to the coolant pipe.

Carefully unbolt the turbo from the exhaust manifold. If the manifold stays on the engine, remove the four nuts securing the turbo to the manifold. If you are replacing the manifold as part of the HKS kit, unbolt the manifold from the head first, then remove the manifold and turbo as an assembly. Lift the old turbo out of the engine bay. Inspect the oil drain pipe and replace the O-ring if necessary.

Installing the HKS 3037A Turbocharger

Before mounting the new turbo, clean the mating surfaces of the cylinder head and exhaust manifold. Use new gaskets throughout. If you are using the HKS exhaust manifold, install it onto the head with new studs and nuts. Torque manifold nuts to factory spec (approximately 35–40 ft-lb) in a crisscross pattern.

Mounting the Turbo

Place a new turbo-to-manifold gasket on the manifold. Position the HKS 3037A onto the manifold studs. The oil drain flange should face downward, and the coolant ports align with your lines. Install the locking nuts and tighten to 30–35 ft-lb, rotating the turbo slightly to ensure the drain line orientation is correct before final torque.

Connect the oil feed line using a new banjo bolt and two copper or aluminum crush washers (one on each side of the fitting). Torque the banjo bolt to 15–20 ft-lb. Attach the oil drain line using the supplied gasket and bolts; tighten evenly to prevent cracking the cast housing. The drain line must slope continuously downward toward the oil pan—no loops or kinks that could restrict drainage.

Connect the coolant feed and return hoses. Use new crush washers for any banjo connections. Route hoses away from hot surfaces and secure with zip ties if needed.

Actuator and Wastegate Setup

The HKS 3037A comes with an internal wastegate actuator. Adjust the actuator arm so that the wastegate flap closes fully when the actuator is installed. A preload of 2–3mm on the actuator rod is typical; this corresponds to a base boost pressure of around 7–8 psi. After initial installation, use a pressure source (like a bicycle pump with a gauge) to verify the actuator opens at the specified pressure (consult HKS instructions). If you plan to run higher boost, install a boost controller in the line between the compressor outlet and the actuator.

Intercooler and Pipe Routing

For the 3S-GTE, a front-mount intercooler (FMIC) is almost mandatory when using the 3037A due to the increased airflow. Mount the FMIC in front of the radiator, using brackets provided with your kit or custom fabrication.

Connect the compressor outlet to the intercooler inlet using 2.5″ or 3″ aluminum piping and silicone couplers. The HKS turbo typically has a 2.5″ outlet. Use beaded or flanged pipe ends and T-bolt clamps to prevent blow-off under boost. Install the blow-off valve on the cold side pipe near the throttle body—mount it as close as practical to reduce surge risk.

Route the piping carefully to avoid rubbing against the chassis, fan shroud, or engine belts. Use a boost leak tester (pressurize the system to 20 psi) to identify any leaking connections before starting the engine. Even a small leak causes lean conditions and poor performance.

Reassembly, Fluids, and First Start

Reinstall any heat shields and undercovers that were removed. Double-check that all wiring connectors and vacuum hoses are secure. Fill the engine with fresh oil (approximately 4.5–5.0 quarts depending on pan) and new filter. Refill coolant using the proper bleed procedure for the 3S-GTE (open the bleed valve on top of the heater pipe while filling).

Oil Prime Procedure

Before cranking the engine, prime the oil system to prevent dry start on the new turbo bearings. Disable the fuel pump (pull the EFI fuse or relay) and crank the engine in 10-second bursts until the oil pressure light goes out (or the gauge shows pressure). This may take three to five cranking intervals. Reconnect the fuel pump fuse.

Initial Start and Break-In

Start the engine and let it idle. Check for oil leaks at the turbo feed and drain, coolant leaks, and exhaust leaks at each joint. Monitor the boost gauge while revving—the engine should build at least 5–7 psi idle or light throttle. Let the engine reach operating temperature and then shut off. Check all fluid levels again.

Do not drive hard immediately. Perform a turbo break-in cycle: drive gently under light boost (under 5 psi) for 50–100 miles, varying engine speed without sustained high load. This allows the turbo bearings to seat properly. After break-in, increase boost gradually while monitoring air-fuel ratios.

Final Adjustments and Tuning

The HKS 3037A will not reach its potential without proper engine management. At minimum, you need a piggyback fuel computer (e.g., Greddy E-Manage, AEM F/IC) or a full standalone ECU (e.g., Link, Haltech, MoTeC) to adjust fuel maps, ignition timing, and boost control. If the engine uses a MAF sensor, consider converting to MAP-based tuning to handle increased airflow.

Set base boost using the actuator (8–10 psi is safe for initial mapping). Then use a boost controller to increase boost in small increments while verifying knock-free operation. On the 3S-GTE, safe boost levels with the 3037A on 93 octane pump gas are typically around 18–22 psi, yielding 350–400 whp with proper supporting mods (fuel pump, 750cc+ injectors, intercooler, exhaust). For 500+ whp, you need E85 or race fuel, ported heads, and upgraded intake manifold.

Always have a professional tuner with 3S-GTE experience perform final calibration on a chassis dynamometer. Improper tuning can destroy the engine quickly.

External Resources and Next Steps

For official HKS product specifications and instructions, visit HKS USA. For community support and wiring diagrams, the MR2 Owners Club and AllTrac.net forums are invaluable. A comprehensive tuning guide can be found at 3S-GTE Tuning Resource (example – verify current link).

Remember that forced induction modifications may affect vehicle emissions legality. Check local regulations before modifying your car. With careful installation and tuning, the HKS 3037A turbo turns the 3S-GTE into a formidable powerplant that delivers thrilling performance for street and track.