Upgrading the turbocharger on your MazdaSpeed3 (MS3) is one of the most effective ways to unlock serious horsepower and torque gains. The ATS Big Turbo Kit is a popular choice among enthusiasts because it delivers a substantial power increase while maintaining reliability when properly tuned. This guide will walk you through the entire installation process, from gathering the right tools to verifying the system after the first startup. Whether you are an experienced DIY mechanic or a dedicated hobbyist, following these steps will help you complete the installation safely and efficiently.

Tools and Materials Needed

Before you start, assemble all the tools and parts. Having everything on hand will save time and prevent frustrating interruptions. The ATS Big Turbo Kit typically includes the turbocharger itself, a new exhaust manifold (if not using the stock one), gaskets, oil and coolant lines, and hardware. You will also need several additional items for a complete installation.

  • ATS Big Turbo Kit (complete with gaskets and hardware)
  • Socket set (metric, 8mm to 19mm) with extensions and universal joints
  • Combination wrenches (10mm, 12mm, 14mm, 17mm, 19mm)
  • Torque wrench (range 5–100 ft-lb)
  • Pry bar and pick set for stubborn clips
  • Oil catch can (highly recommended to reduce carbon buildup)
  • Intercooler piping kit with silicone couplers and T-bolt clamps
  • Gasket maker (high-temp RTV silicone, such as Permatex Ultra Copper)
  • Brake cleaner and shop towels for cleaning surfaces
  • Thread locker (medium strength, blue Loctite)
  • New oil and filter (full synthetic 5W-30 recommended)
  • Cruise control bracket relocation kit (if your MS3 has cruise control)
  • Boost leak tester (can be homemade or purchased)

Optional but recommended: a wideband oxygen sensor and a boost gauge to monitor air-fuel ratio and boost pressure during the tuning phase. You may also need a laptop with tuning software (such as Cobb Accessport or VersaTuner) to adjust the ECU after installation.

Preparation and Safety

Park your MazdaSpeed3 on a level, solid surface. Ensure the engine has completely cooled down. Working on a hot engine increases the risk of burns and makes it harder to break bolts loose. Disconnect the negative terminal of the battery and set it aside to prevent accidental shorts or electrical damage while you disconnect sensors and components.

It is wise to drain the engine oil and coolant before beginning the turbo removal. Even if you plan to reuse them, draining reduces the mess when you disconnect oil and coolant lines. Remove the engine undercover (if equipped) and place drain pans under the oil pan and radiator drain plug.

Take photos of the stock turbo setup and routing of hoses, wires, and vacuum lines. This documentation helps during reassembly, especially if your ATS kit uses some of the original plumbing.

Remove the Intake System and Battery

Start by removing the air intake assembly. Unbolt the factory air box, mass air flow sensor, and snorkel. Carefully unclip the electrical connector from the MAF sensor and set the assembly aside. Remove the battery along with its tray – this creates clearance to access the turbo area from the passenger side. You will also need to remove the battery tray to make room for the new turbo's intake plumbing and oil lines.

Remove the Factory Intercooler and Piping

The stock intercooler sits on top of the engine. Disconnect the charge pipes from the intercooler and from the turbo outlet. Remove the intercooler by unbolting its mounting bracket and lifting it out. Leave the hard pipes and couplers out; they will be replaced by the new intercooler piping included with the ATS kit (or your own aftermarket piping).

Removing the Factory Turbocharger

With the intake, battery, and intercooler out of the way, you have clear access to the turbo. Follow these steps precisely to avoid damaging components.

  1. Disconnect the exhaust downpipe: Unbolt the downpipe from the turbo outlet. You may need to remove the heat shield and a few bolts at the bellhousing. Use penetrating oil on the bolts if they are seized.
  2. Remove the oil feed line: The oil feed line runs from the engine block to the turbo. Use a flare nut wrench to loosen the banjo bolt or line fitting. Have a rag ready to catch residual oil.
  3. Disconnect the coolant lines: There are two coolant lines – an inlet and an outlet. Pinch the rubber hoses with clamps or use a small hose plug to minimize coolant loss. Unbolt the fittings from the turbo.
  4. Unbolt the turbo from the exhaust manifold: The stock K04 turbo is bolted to the exhaust manifold with four nuts. Working from underneath and above, remove these nuts. A universal joint on your socket extension helps reach the lower nuts.
  5. Carefully lift the turbo out: Wiggle the turbo free. Be careful not to drop any bolts or debris into the open exhaust ports. If the turbo feels stuck, check for any hidden bolts or brackets (e.g., a support bracket near the compressor outlet).

Once removed, inspect the exhaust manifold flange for any warping or cracks. The ATS kit may include a new manifold; if you are reusing the stock manifold, it is a good time to have it resurfaced or replaced.

Preparing the Installation Area

Clean the exhaust manifold flange with brake cleaner and a scraper to remove all old gasket material. Wipe down the turbo mounting area on the engine block. Install the new oil drain gasket (supplied with the ATS kit) onto the oil pan or drain port, depending on your kit configuration. Apply a thin bead of high-temp RTV to the gasket for extra sealing.

If your ATS Big Turbo Kit includes an upgraded exhaust manifold, install it now. Torque the manifold bolts to the manufacturer's specification (typically 30–35 ft-lb in a crisscross pattern). Use thread locker on the bolts to prevent loosening from thermal cycling.

Installing the ATS Big Turbo Kit

Now comes the exciting part – setting the new turbo into place. Follow these steps to ensure a proper, leak-free installation.

  1. Mount the turbo: Position the ATS turbo onto the exhaust manifold studs. Use new locking nuts (included) and tighten them to the specified torque (consult the ATS manual; generally 25–30 ft-lb). Make sure the turbo sits square and does not bind against any other components.
  2. Connect the oil feed line: Attach the new oil feed line supplied with the kit. Apply a small amount of thread sealer to the banjo bolt threads (not the sealing face). Tighten to 15–20 ft-lb. Double-check that the line does not rub against the manifold or engine.
  3. Connect the coolant lines: Install the new coolant hoses, using the supplied fittings and clamps. Route them away from heat sources and moving parts. Use zip ties to secure them if needed. Torque the banjo bolts to specification.
  4. Reinstall the oil drain line: The oil drain line returns oil to the pan. Ensure the rubber hose has room to flow freely; any kinks will cause oil backup and turbo seal failure. Secure with clamps.
  5. Install the downpipe: Use the new downpipe that came with the kit (or your existing downpipe if compatible). Apply a thin layer of copper anti-seize to the studs and tighten the nuts evenly. A three-bolt flange should be torqued to 25 ft-lb.

Important: The ATS Big Turbo Kit often requires oil restrictor placement. Check the kit instructions – if a restrictor is needed, install it inline on the oil feed before the turbo. Over-oiling can cause smoke and leaks.

Intercooler Piping and Intake Setup

The larger turbo requires larger charge pipes and a new intake system. Install the intercooler piping provided with the kit or your chosen aftermarket pipes. Use silicone couplers and T-bolt clamps for a secure, leak-free fit. Tighten clamps to 5–6 ft-lb (do not overtighten – it can cut the silicone).

For the intake side, the ATS turbo typically uses a larger compressor inlet. Attach the silicone intake hose from the MAF housing to the turbo. You may need to relocate the MAF sensor or use a blow-through setup if your kit demands it. If the kit includes a blow-off valve (BOV) flange, install the BOV now – a reliable aftermarket unit is recommended for high boost levels.

Check clearance of all piping against the hood, engine, and chassis. Use plastic ties or aluminum tape to protect wires and hoses from rubbing on the pipes.

Reassembly and Final Connections

Reinstall the battery tray and battery, followed by the intake manifold if it was removed. Connect all vacuum lines according to your photos. If the kit uses a new boost control solenoid or electronic boost controller, wire it according to the instructions and route the vacuum lines to the wastegate actuator.

Install the oil catch can in the PCV system to minimize oil vapor entering the intake. This step is strongly recommended for direct injection engines like the MS3 because it keeps valves clean.

Reconnect the MAF sensor, all electrical connectors, and the negative battery terminal. Double-check every hose clamp, bolt, and electrical connection before proceeding.

Verification and Leak Testing

Before starting the engine, perform a boost leak test. Use a boost leak tester attached to the turbo inlet (or MAF housing). Pressurize the system to 15–20 psi and listen for hissing sounds. Check all couplers, the BOV, and the intake manifold gasket. Tighten any leaking connections. This step is critical – a small leak can cause poor running, lean conditions, and even engine damage.

Next, prime the turbo oil system. With the spark plugs removed or the fuel pump fuse pulled, crank the engine for 10–15 seconds to build oil pressure. This ensures oil circulates to the turbo bearings before the first start. Reinstall the spark plugs and fuse.

First Startup and Break-In

Start the engine and let it idle. Listen for any unusual noises like scraping, whistling, or excessive exhaust leaks. Check the turbo for oil or coolant leaks while the engine warms. Allow the engine to reach operating temperature; watch the oil pressure gauge (if you have one).

During the first few minutes, keep the engine speed below 3,000 RPM. The turbo bearings need a break-in period of approximately 500 miles before full power is used. Vary engine speed during this break-in, avoid steady highway cruising, and do not exceed 10 psi of boost.

After a short drive, check all fluids and look for leaks again. Torque the downpipe nuts and charge pipe clamps after heat cycling.

Tuning: Unlocking the Full Potential

The ATS Big Turbo Kit will not perform correctly without a proper tune. The factory ECU cannot compensate for the increased airflow and larger injectors many kits require. You have two main options: a custom tune using software like Cobb Accessport, VersaTuner, or EcuTek, or a remote tune from a reputable tuner. Many ATS customers use the free tunes provided by ATS, but a custom tune from a professional tuner who knows the MS3 platform is highly recommended for safety and maximum power.

Send your tuner a log of the first drive (idle, cruise, light load) so they can adjust fuel and timing columns. Do not attempt to boost the engine without tuning. Running lean can destroy the engine in seconds.

Maintenance After Installation

With the larger turbo, maintenance intervals change. Change engine oil every 3,000–4,000 miles. Inspect the oil catch can and empty it frequently. Check all charge pipe clamps for tightness monthly. Monitor boost levels and look for any signs of oil in the intercooler piping – that could indicate a failing turbo seal or a clogged oil drain.

Consider upgrading the fuel pump and injectors if you plan to run higher boost (over 20 psi). The stock fuel system will run out of capacity quickly after a turbo upgrade.

Conclusion

Installing an ATS Big Turbo Kit on your MazdaSpeed3 is a demanding but highly rewarding project. With careful preparation, attention to detail, and proper tuning, you can transform your MS3 into a street weapon with over 350 wheel horsepower on pump gas. This guide covered the core steps, but always refer to the specific instructions that came with your kit and your vehicle service manual. For additional support, visit the ATS Racing website for product details and tuning resources, and join the MazdaSpeed forums to learn from other builders. For general turbo installation tips, How to Turbo offers excellent guidance. Take your time, follow the steps, and enjoy the thrill of a properly tuned big-turbo MS3.