Introduction

Upgrading the turbocharger on a Mazda Mazdaspeed3 (MS3) is one of the most effective ways to unlock significant horsepower and torque gains. The Precision 5857 turbocharger offers a proven balance of quick spool and high-flow capacity, making it a popular choice for MS3 owners targeting 400–500 wheel horsepower. This expanded guide covers every step of the installation, from tools and preparation to final testing, with detailed notes on common pitfalls, torque specifications, and required supporting modifications.

Whether you are a seasoned DIY enthusiast or a first-time turbo swapper, careful attention to each stage will ensure a reliable and powerful setup. While this kit is designed to be a direct-fit upgrade for the Mazdaspeed3’s factory turbo location, some modifications to intercooler piping, heat shielding, and tuning are essential. For reference, Precision Turbo’s official product page provides the full spec sheet for the 5857 (Precision 5857 Turbo Specs).

Tools and Materials Needed

Having the correct tools and parts on hand before beginning will save hours of frustration. Beyond the turbo itself, you will need a turbo installation kit designed for the MS3, which typically includes gaskets, oil line fittings, and hardware. Below is a comprehensive list:

  • Precision 5857 Turbocharger – ensure it includes the correct turbine housing (usually .72 A/R or .63 A/R for quick spool).
  • Turbo installation kit – includes copper or banjo washers, crush washers, oil feed restrictor, and stainless steel braided lines.
  • Socket and ratchet set – metric sockets from 8mm to 19mm, plus 1/2" drive for torque wrench.
  • Wrenches – combination wrenches (10mm, 12mm, 14mm, 17mm, 22mm for O2 sensors).
  • Torque wrench – needed for exhaust manifold bolts and turbo flange bolts (range 15–50 ft-lb).
  • Intercooler piping and silicone couplers – the 5857’s compressor outlet and inlet may require 2.5” or 3” silicone bends. Confirm fitment with your existing cold-side piping.
  • Oil feed and drain lines – the factory oil drain is typically 5/8” ID; a new drain line with -10 AN or -12 AN fitting is recommended. A steel-braided feed line with -4 AN fitting works best.
  • Gaskets and seals – exhaust manifold gasket, turbo to manifold gasket, downpipe gasket, and O-ring for the coolant return.
  • Engine oil – high-quality 5W-30 or 0W-30 synthetic (to pre-lube the turbo).
  • Coolant – OEM Mazda FL22 or equivalent.
  • Anti-seize compound – for exhaust bolts to prevent future seizing.
  • Thread-locker (blue) – for critical fasteners like the oil feed union.
  • Jack and jack stands – the car must be raised for access to the turbo underneath.
  • Shop towels and brake cleaner – to clean surfaces before reassembly.

For a complete recommended parts list, refer to dedicated Mazdaspeed forums such as this Precision 5857 installation FAQ.

Preparation Steps

Preparation directly affects how smoothly the installation proceeds. Begin by parking the MS3 on a level surface with the engine cold. Disconnect the negative battery terminal to prevent electrical shorts and accidental fuel pump activation. Remove the engine cover and any sound-deadening material in the engine bay that obstructs access to the turbo area.

Drain the coolant from the block into a clean container (the coolant lines will be disconnected). Optionally, drain the engine oil to make it easier to reach the oil drain pan. Removing the splash shield under the car gives better access to the downpipe and turbo oil drain.

Label all vacuum lines and connectors with tape or zip ties before disconnecting. The factory turbo inlet pipe, boost control solenoid hoses, and wastegate actuator line are easily mixed up. Take photos of the stock setup for reference. Finally, spray penetrating oil on the exhaust manifold nuts, downpipe bolts, and O2 sensor threads; allow it to soak for 20 minutes to reduce the chance of snapping bolts.

Removing the Stock Turbocharger

The factory K04 turbo is compact but tightly packaged. Patience is key to avoid damaging surrounding components. Follow these steps in order:

Step 1: Disconnect Intake and Boost Piping

  • Remove the intake air filter box and tube.
  • Disconnect the MAF sensor connector.
  • Loosen the clamps on the cold-side intercooler pipe at the throttle body and remove the pipe assembly.
  • Remove the factory blow-off valve if it is attached to the pipe.

Step 2: Disconnect Oil and Coolant Lines

  • Locate the oil feed line on top of the turbo. Use a 17mm crows foot or flare wrench to loosen the banjo bolt. Capture any residual oil.
  • Unbolt the oil drain flanges from the turbo and the engine block (two 10mm bolts). The drain hose is usually spring-clamped; have a drain pan ready.
  • Disconnect the coolant feed and return lines. These are 10mm banjo fittings and will spill coolant. Plug the lines immediately with rubber caps or vacuum caps.

Step 3: Unbolt the Turbo from the Exhaust Manifold

  • Remove the heat shield over the turbo (three 10mm bolts).
  • Using a 12mm or 14mm socket, remove the four nuts securing the turbo to the exhaust manifold. They are accessed from underneath the car and from above with a long extension.
  • Carefully slide the turbo off the studs. It may require gentle prying with a plastic trim tool. Avoid damaging the manifold studs.
  • Remove the turbo from the engine bay. This is easier if you tilt it forward and lift out from the driver’s side.

Step 4: Remove the Downpipe

  • Unbolt the downpipe from the back of the stock turbo (three 12mm nuts).
  • Lower the downpipe from the vehicle. The O2 sensor may need to be unthreaded using a 22mm wrench.

Inspect the exhaust manifold studs for damage. Replace any that are bent or stripped. Clean the manifold surface with a wire brush and brake cleaner.

Installing the Precision 5857 Turbo

With the stock unit out, the new turbo can be installed. The Precision 5857 is slightly larger than the K04, so plan for some clearance adjustments. The following sequence ensures correct alignment and torque.

Prepping the New Turbo

  • Remove the protective plugs from the oil inlet and outlet of the 5857.
  • Prime the turbo by pouring a few ounces of clean engine oil into the oil feed port and spinning the compressor wheel by hand. This lubricates the journal bearings before first start.
  • Attach the included oil feed restrictor (usually 0.040” to 0.050” orifice) to the turbo’s oil inlet. Use thread sealant on the fitting but avoid Teflon tape near the bearing housing.

Mounting the Turbo to the Manifold

  • Install a new exhaust manifold gasket onto the manifold studs. Apply anti-seize to the stud threads.
  • Align the 5857 turbine housing with the studs. The turbo should sit square; if not, the oil drain orientation may need adjustment.
  • Thread the four nuts onto the studs. Torque them to 30 ft-lb in a cross pattern to ensure even clamping.
  • If the turbo’s internal wastegate actuator bracket interferes with the manifold, a small spacer or bracket modification may be required. Many aftermarket MS3 turbo kits include a bracket relocation plate. Check clearances before final tightening.

Connecting Oil and Coolant Lines

  • Oil feed: Connect the -4 AN braided line from the engine block oil feed port (usually near the oil filter housing) to the turbo inlet. Use the supplied banjo or AN fitting. Torque the union fitting to 18-22 ft-lb (overtightening can collapse the restrictor).
  • Oil drain: Attach the new silicone or rubber oil drain hose (5/8” ID) to the turbo’s 1/2” NPT drain fitting. Use a high-quality hose clamp. Route the hose downward to the engine block drain port. Ensure the hose has a continuous downhill slope with no kinks.
  • Coolant lines: Most 5857 kits do not include water cooling; if you choose to use coolant, follow the manufacturer’s instructions. For simplicity, many owners cap the coolant ports. However, running coolant can extend turbo bearing life. If using coolant, connect the factory banjo lines to the 5857 coolant fittings (often 1/8” NPT). Use new copper washers and torque to 15 ft-lb.

Attaching the Downpipe and Wastegate

  • Install a new downpipe gasket on the turbine outlet. The 5857 uses a standard T3/T4 flange; your downpipe should match. If using an aftermarket downpipe with a catalytic converter, ensure it clears the larger turbine housing.
  • Bolt the downpipe to the turbo using three 12mm nuts. Torque to 25 ft-lb.
  • Connect the wastegate actuator arm to the wastegate flapper on the turbine housing. Adjust the actuator rod length to achieve 8–10 psi of boost spring tension. Secure the arm with the provided cotter pin.
  • If running an external wastegate (common on high-horsepower builds), weld the appropriate flange onto the downpipe and route the dump tube.

Connecting the Intercooler Piping

The Precision 5857’s compressor outlet is typically 2.5” (or 3” with a different cover). The MS3’s factory intercooler piping is 2.5”, but the larger turbo may require modified routing to avoid rubbing against the alternator or power steering lines.

Inlet Side (Cold Side)

  • Attach a silicone coupler and T-bolt clamp to the turbo inlet (3” opening). Connect this to the intake duct or a larger MAF housing if upgrading.
  • If retaining the factory airbox, you may need a reducer coupler to match the turbo’s compressor inlet.

Outlet Side (Hot Side)

  • Install a short silicone elbow onto the compressor outlet (2.5” ID). Route the pipe toward the passenger side of the engine bay, clearing the alternator.
  • Use the factory intercooler but be aware that the stock side-to-side IC becomes a restriction above 400 hp. A larger front-mount intercooler (FMIC) is highly recommended for the 5857.
  • Secure all couplers with T-bolt clamps (not worm-style clamps) to prevent blow-off at high boost.

If you are using an aftermarket FMIC kit, follow that kit’s piping diagram. Ensure the hot-side charge pipe does not contact the AC line or the radiator fan. Use silicone hump couplers to provide flex and reduce stress on the turbo flange.

For detailed piping layouts, the Edge Autosport MS3 FMIC installation guide offers helpful visual references.

Finalizing the Installation

All connections must be verified before startup. Perform these checks in order:

  • Reconnect the intake piping from the MAF sensor to the turbo inlet. Tighten all clamps.
  • Reinstall the engine harness connectors for the MAF, O2 sensors, and any vacuum sensors that were detached.
  • Connect the battery terminal. Do not start the engine yet.
  • Fill the engine with fresh oil (5W-30 synthetic) and new filter. The 5857’s oil capacity is supplemented by the engine oil; no separate oil supply is needed.
  • Refill the cooling system with Mazda FL22 coolant. Use a funnel to slowly fill the radiator and overflow tank. Leave the radiator cap off during the next step.
  • Check all bolts and fasteners one last time: turbo-to-manifold nuts, downpipe bolts, intercooler couplers, oil drain clamp, wastegate lock nut.
  • If you have access to a boost leak tester, pressurize the intake system to 20 psi and listen for leaks. Spray soapy water on every coupler and line connection.

Testing the Installation

The first startup is critical. Follow this procedure to protect the new turbo:

  • Disable the fuel pump or pull the fuel pump fuse, then crank the engine for 10 seconds to build oil pressure without firing. Reconnect the fuse.
  • Start the engine and let it idle at 900–1000 rpm for at least 5 minutes. During this time, oil pressure must reach 20–30 psi. Monitor the oil pressure gauge.
  • Check for oil leaks at the turbo feed line, drain line, and exhaust manifold gasket. Also inspect coolant leaks.
  • Listen for abnormal noises: a faint whistling is normal; a grinding or scraping sound indicates contact between the compressor wheel and housing.
  • Allow the engine to reach operating temperature, then rev to 2000–3000 rpm in neutral for 30 seconds. Listen again for boost leak sounds.
  • If everything sounds and looks normal, perform a short test drive staying under 3000 rpm and below 5 psi of boost. Gradually increase load over 20 miles, monitoring boost pressure and air/fuel ratios (if you have a wideband gauge).

A boost leak test after the first drive will catch any loose clamps. The 5857 should spool noticeably earlier than the stock K04—expect full boost around 3500–4000 rpm depending on your tuning. Be aware that the stock ECU will not manage the larger turbo’s fuel and timing demands. You must have a custom tune from a reputable Mazdaspeed tuner (e.g., Freektune, Purple Drank, or Dynotronics) before pushing full throttle. Driving without a tune risks severe engine knock.

Performance Expectations and Tuning Considerations

The Precision 5857 on the Mazdaspeed3 is capable of 400–480 whp on pump gas with supporting mods (fuel pump internals, injectors, and a front-mount intercooler). On E85, 500+ whp is achievable. However, the turbo’s response is still street-friendly, making it a great upgrade for daily drivers who want occasional track power. For comparison, the stock K04 maxes out around 300 whp with a tune. Upgrading to the 5857 requires revisiting the fuel system: the high-pressure fuel pump (HPFP) must be upgraded to prevent fuel pressure drop. A larger aftermarket fuel pump internals kit from Autotech or Corksport is mandatory.

Expect to also upgrade the clutch; the stock clutch slips around 320–350 whp. A stage 2 or 3 clutch (e.g., ACT, South Bend) will handle the torque. Many owners also add a limited-slip differential to put the power down. The Precision 5857 is a journal-bearing turbo; with proper oil cooling and regular changes, it will last 60,000+ miles. For longevity, consider an oil catch can to reduce carbon buildup and keep the turbo bearings clean.

Conclusion

Installing the Precision 5857 turbo on your Mazda MS3 is a rewarding project that transforms the car into a high-horsepower performer. By following the detailed removal, mounting, and testing steps above, you can execute the upgrade confidently while avoiding common mistakes like oil starvation or boost leaks. Remember that the installation is only half the journey; proper tuning, fuel system upgrades, and supporting modifications are crucial to reliability. Take your time, use quality parts, and verify every connection. With the 5857 under the hood, your MS3 will deliver thrilling acceleration and a broad powerband that makes every drive an event. For ongoing community support and tune recommendations, the MazdaspeedForums 5857 owners thread is an invaluable resource.