Upgrading the turbocharger on your Subaru WRX is one of the most effective ways to unlock serious horsepower gains without sacrificing daily drivability. The TD04-L 19T mini turbo is a popular choice among enthusiasts who want a punchy, responsive setup that spools quickly and delivers strong mid-range torque. While the swap is a weekend-project level job, it requires attention to detail, the right tools, and a clear understanding of each step. This guide provides an expanded, step-by-step walkthrough to help you install the TD04-L 19T correctly, avoid common pitfalls, and get the most out of your new turbo.

Why Upgrade to the TD04-L 19T?

The stock TD04 on the WRX is a solid unit, but its small compressor wheel limits top-end airflow. The 19T variant features a larger 19T compressor wheel and a ported shroud, which increases airflow by roughly 10-15% over the stock 15G or 16G found on many early WRX models. This translates to higher boost potential, more power up top, and a broader torque curve—all while keeping spool nearly as quick as the factory turbo. It’s an ideal upgrade for those running a mild tune, upgraded fuel injectors, and a larger intercooler without going to a full aftermarket turbo that requires extensive modifications.

Tools and Materials Needed

Before diving into the installation, gather all necessary tools and parts. Missing an item mid-job can turn a few hours into a multi-day project. Here’s a comprehensive list:

  • TD04-L 19T Mini Turbo – Purchased from a reputable remanufacturer or builder; ensure it comes with the correct actuator and wastegate settings for your WRX model.
  • Full turbo gasket set – Includes inlet gasket, outlet gasket, oil return gasket, and exhaust manifold gaskets. Do not reuse old gaskets.
  • Oil feed line – Either a braided stainless line or OEM replacement. If your stock line is old or crusty, replace it now to prevent leaks.
  • Oil return line – Same as above; inspect the rubber hose for cracks.
  • Intercooler piping kit – Designed specifically for the 19T compressor housing outlet. Many aftermarket kits use silicone couplers and T-bolt clamps.
  • Socket and wrench set – Metric sizes: 10mm, 12mm, 14mm, 17mm, and 19mm. Deep sockets help with tight spaces.
  • Torque wrench – Essential for tightening turbo bolts and manifold studs to spec.
  • Vacuum/pressure lines – For boost reference and wastegate actuation; use silicone lines for durability.
  • Engine oil and filter – After installing, you’ll need fresh oil and a new filter.
  • Coolant – Subaru Super Blue or equivalent; plan on a full drain and refill.
  • Safety glasses, mechanic gloves, jack stands, and a drain pan – Protect yourself and your workspace.

Preparation Steps

Proper preparation saves frustration later. Park the car on level ground, chock the wheels, and disconnect the battery negative terminal. Allow the engine to cool completely—working near a hot exhaust manifold is dangerous and can burn you. Once cool, drain the engine oil and coolant into separate containers. The oil pan plug and radiator drain petcock are straightforward, but be sure to open the reservoir cap to speed coolant drainage. Remove the front bumper cover and the intercooler. On a WRX, the intercooler sits on top of the engine and is held by four bolts; disconnect the recirculation hoses and lift it out. This gives you clear access to the turbocharger.

Removing the Stock Turbo

With the intercooler out, you have a clear view of the turbo mounted on the up-pipe. Follow these steps carefully:

  1. Disconnect intake and exhaust pipes. Loosen the clamps on the intake snorkel and remove the hose from the compressor inlet. For the outlet side, unbolt the downpipe from the turbine housing – note that these nuts are often stubborn; use penetrating oil ahead of time.
  2. Remove the oil feed line. Using a 10mm wrench, disconnect the banjo bolt at the top of the turbo. Have a rag ready to catch residual oil. Separately, unscrew the feed line from the engine block if your setup uses a separate line.
  3. Remove the oil return line. This is a larger rubber hose clamped to the bottom of the turbo and to the oil pan return port. Loosen the clamps and wiggle it free. Expect some old oil to drip.
  4. Unbolt the turbo from the exhaust manifold. There are four nuts holding the turbo to the up-pipe flange. Use penetrating oil if they are rusted. A 14mm socket usually fits. Remove the heat shield bolts first if needed.
  5. Lift the stock turbo out. Maneuver it carefully past the engine block and the frame rail. It may help to rotate the turbo to pull it upward. Place the old unit aside; you may want to keep the core as a core return for a remanufactured unit.

Inspect the up-pipe gasket surface; clean any remaining gasket material with a scraper. If the studs are damaged, replace them now.

Installing the TD04-L 19T Mini Turbo

Installation is essentially the reverse of removal, but with extra care for the new turbo:

  • Position the new turbo onto the up-pipe flange. Place a new exhaust manifold gasket between the turbo and up-pipe. Hand-tighten the four nuts to align the turbo.
  • Torque the turbo bolts to specification. Typically, Subaru specs call for 28–33 ft-lbs (38–45 Nm) on a clean, lightly oiled thread. Do not overtighten as the studs can snap. Use a crisscross pattern.
  • Reconnect the oil feed line. Use a new copper or aluminum washer on the banjo bolt. Torque the banjo bolt to 15–20 ft-lbs (20–27 Nm). If your feed line is a hard line, ensure it does not kink.
  • Attach the oil return line. Slip the hose onto the turbo's return nipple and secure it with a high-quality worm gear clamp or T-bolt clamp. Route it downward without sharp bends. Connect the other end to the oil pan return port, using a new gasket if applicable.
  • Connect intake and exhaust pipes. Slide the intake hose back onto the compressor inlet and tighten the clamp. Bolt the downpipe to the turbine outlet using new gaskets; torque to 25–30 ft-lbs (34–40 Nm).

Take a moment to check that all clamps, hoses, and bolts are tight. Spin the compressor wheel by hand to ensure it rotates freely without binding. If the wheel rubs the housing, the turbo may be defective – do not proceed.

Connecting the Intercooler and Piping

The 19T compressor outlet is larger than the stock TD04 outlet, so you will need a specific intercooler piping kit or a silicone reducer coupler. Many aftermarket kits include a larger-diameter Y-pipe and longer hoses to accommodate the repositioned outlet. Work your way through these steps:

  • Install the new intercooler piping per the kit instructions. Most kits connect the compressor outlet to the intercooler inlet with a silicone coupler and T-bolt clamps.
  • Reinstall the intercooler. Ensure the intercooler outlet hoses fit snugly over the throttle body. Tighten all clamps evenly to prevent boost leaks.
  • Double-check that the turbo-to-intercooler pipe does not rub against the engine or frame. If it contacts metal over time, the hose can wear through and cause a leak.

Boost leaks are a common source of poor performance after a turbo swap. Consider performing a boost leak test using a homemade tester before starting the engine.

Final Steps: Fluids, Start-Up, and Leak Check

Before turning the key, complete these tasks:

  • Replace the oil filter and fill the engine with fresh oil. Due to the dry turbo, it is a good idea to pre-lube the turbo by pouring a small amount of oil into the feed port and spinning the wheel gently.
  • Refill the cooling system with the correct coolant mixture. Bleed the system by loosening the bleeder screw on top of the thermostat housing.
  • Reconnect the battery. Turn the ignition to “on” without starting to prime the fuel system.
  • Start the engine and let it idle for 10–15 minutes. During this time, inspect all turbo connections for oil or coolant leaks. Listen for unusual whining or scraping noises from the turbo.
  • Shut the engine off and recheck the oil level. Top off as needed.

If you have a boost gauge and an aftermarket boost controller, now is the time to adjust wastegate duty cycle. Do not run high boost without a proper tune.

Tuning After Installation

A larger turbo requires a custom tune to run safely. The 19T will move more air than the stock turbo, and without recalibrating the fuel and ignition maps, you risk running lean or knocking. Find a reputable Subaru tuner or use an open-source tuning solution like RomRaider. Specify that you have a TD04-19T and any other modifications (injectors, fuel pump, intercooler). Most owners see peak power around 18–20 psi with safe timing and fueling. Expect around 280–320 whp depending on supporting mods.

Common Issues and How to Avoid Them

Several problems can arise during and after the install:

  • Oil leaks. Usually caused by a reused gasket or a warped flange. Always use new gaskets and ensure the up-pipe surface is flat.
  • Boost creep. The larger turbine housing may not bypass enough exhaust gas with the stock wastegate. Porting the wastegate passage or using an external wastegate can solve this.
  • Over-speeding the turbo. Running boost above 22 psi on the 19T can overspin the small compressor wheel, leading to premature failure. Keep boost reasonable.
  • Incorrect oil drain. If the oil return line has a kink or is too small, oil pressure will build and blow out seals. Ensure a straight, downhill drain path.

For further troubleshooting, consult this IWSI turbo install forum for real-world solutions.

Test Drive and Break-In

After confirming no leaks and stable idle, take the car for a gentle test drive. Keep engine speed below 3000 rpm for the first 20 miles to allow the new turbo bearings to break in. Then, gradually increase load and watch boost pressure. Listen for any unusual sounds. Once confident, perform a few full-throttle pulls in third gear to verify the tune works properly. Monitor your wideband air-fuel ratio; aim for 11.5–12.0:1 under boost.

Conclusion

Installing a TD04-L 19T mini turbo is a rewarding upgrade that delivers noticeable performance gains without the complexity of a larger aftermarket turbo. By following this expanded guide, using fresh gaskets, and paying close attention to oil and coolant connections, you can complete the swap in a weekend and enjoy a more responsive, powerful WRX. Always remember that a proper tune is non-negotiable—investing in a custom calibration will protect your engine and squeeze every bit of power from your new turbo. For more detailed specs, visit Scoobypedia’s 19T comparison page.