Understanding the APR Stage 2 Turbo System

The APR Stage 2 Turbo System is a comprehensive upgrade package engineered specifically for the Mitsubishi 4B11T engine found in models such as the Lancer Evolution X. Unlike a simple bolt-on turbocharger swap, this system is designed as an integrated solution that includes a larger compressor wheel, an optimized turbine housing, and a high-flow intercooler core. The result is a significant increase in airflow capacity, allowing the engine to produce substantially more power while maintaining drivability and reliability under moderate boost levels.

Key components of the APR Stage 2 kit include a replacement turbocharger with a billet compressor wheel, a bar-and-plate intercooler that offers improved heat rejection over the factory unit, and cast aluminum inlet and outlet pipes that reduce flow restrictions. All necessary gaskets, clamps, and hardware are included to facilitate a direct installation. The system is often paired with APR’s own calibration software, but it can also be tuned by aftermarket specialists using platforms like EcuTek or Cobb Accessport.

This upgrade targets enthusiasts who want a noticeable step up from the stock turbo without moving to a full-blown Stage 3 setup that requires extensive internal engine work or fueling modifications. When properly installed and tuned, the APR Stage 2 system can support power levels in the 350–400 whp range, depending on the supporting modifications and fuel quality used.

Complete Cost Breakdown: $3,500 Budget

The following breakdown covers the primary expenses associated with the APR Stage 2 turbo upgrade for the 4B11T. Prices are based on current market averages in the United States and may vary by region and vendor.

  • APR Stage 2 Turbo Kit (including turbo, intercooler, pipes, hardware): $2,200
  • Professional Installation Labor: $800
  • Custom Tuning (dyno session and ECU calibration): $500
  • Contingency budget for incidental items (gaskets, fluids, fasteners): $100

Total baseline: approximately $3,600, though $3,500 is a realistic target if you source the kit on sale or negotiate labor rates. Each of these cost categories warrants further examination.

1. APR Stage 2 Turbo Kit

The kit itself represents the largest single expense at roughly $2,200. This price typically includes the following:

  • Billet compressor turbocharger (journal bearing or ball bearing, depending on revision)
  • Cast aluminum turbo inlet pipe and outlet piping
  • High-capacity bar-and-plate intercooler (core size approximately 3.5–4 inches thick)
  • Silicone couplers and t-bolt clamps
  • Exhaust manifold gasket, turbo-to-downpipe gasket, and oil feed/return lines
  • Mounting hardware and installation instructions

Some retailers may offer the kit without the intercooler for a lower price, but the intercooler upgrade is strongly recommended to keep charge air temperatures in check. If you already have an upgraded intercooler from a previous setup, you could potentially save $300–$500 by purchasing the bare turbo and piping, but the full kit provides a plug-and-play solution.

2. Installation Labor

Professional installation is strongly advised because of the complexity involved in removing the factory turbo and fitting the larger APR components. Labor costs for a job like this at a reputable performance shop typically range from $600 to $1,000, with $800 being a common middle ground. The installation process generally includes:

  • Draining coolant and oil, and removing the factory turbo, intercooler, and associated piping
  • Cleaning mounting surfaces and installing new gaskets
  • Fitting the new turbo and intercooler, ensuring proper alignment of all hoses and clamps
  • Replacing any worn vacuum lines or couplers as needed
  • Priming the oil system and pressure-testing for leaks before startup
  • Road-testing to verify boost control and base functionality

If you are mechanically experienced and have access to a lift and proper tools, you can reduce this cost to zero. However, many enthusiasts find that the time saved and the assurance of a leak-free install are worth the labor fee.

3. Tuning Costs

A conservative flash tune from APR using their proprietary software is sometimes included in the kit price when purchased directly. But most enthusiast-owned vehicles require custom tuning to dial in fuel timing, boost levels, and ignition advance for a specific setup. Custom tuning runs approximately $400–$600, broken down as follows:

  • Dyno time: 1–2 hours at $100–$150 per hour
  • ECU reflash or reflash license: $150–$300 (if not already owned)
  • Data logging and road tuning to finalize part-throttle behavior

An optional upgrade to a stand-alone engine management system (e.g., Motec or Link) can add $1,000–$2,500 but is rarely necessary for a Stage 2 build. Stick with a reliable ECU reflash from a tuner experienced with the 4B11T platform.

While the $3,500 budget covers the core kit, installation, and tuning, you should plan for supporting modifications that ensure the engine can handle the increased airflow safely. These are not optional luxuries—they are essential for reliability and full power output.

Fuel System Upgrades

The stock fuel system on the 4B11T can support roughly 350–380 whp with proper tuning, but the APR Stage 2 system often pushes beyond that threshold on E85. Consider these upgrades:

  • High-flow fuel injectors: 800–1000 cc/min (approx. $400–$600)
  • In-tank fuel pump: Walbro 450 or AEM 340 (approx. $150–$250)
  • Fuel pressure regulator: Optional for E85, recommended for consistent pressure (approx. $150)

If you plan to run pump gas only, the stock injectors and pump may suffice up to 370 whp. But for E85 or higher boost, the fuel system becomes a limiting factor. Budget an additional $600–$1,000 if fuel upgrades are needed.

Exhaust System

The APR Stage 2 turbo has a larger turbine outlet than stock, so a 3-inch downpipe and cat-back exhaust significantly reduce backpressure and help the turbo spool efficiently. A turbo-back exhaust system (downpipe, high-flow catalytic converter, and mid-pipe) costs $600–$1,200. If you already have a quality 3-inch downpipe, you may only need a cat-back section. A full system improves power by 10–15 whp typically.

Intake System

The APR kit includes a new intake pipe, but an open-element cold air intake is often added to reduce intake restriction. A quality intake (e.g., ETS, AMS) runs $250–$400. This also provides more audible turbo spool, which many enthusiasts enjoy.

Cooling System

Higher boost levels increase engine stress and heat. Upgrading the radiator to a larger aluminum unit ($300–$500) and using a high-pressure radiator cap can prevent overheating during track sessions. Additionally, an oil cooler (approx. $300–$600) is wise if you plan to drive aggressively or live in a warm climate.

Performance Expectations and Dyno Results

With the APR Stage 2 system, proper fueling, and a good tune, a 4B11T engine can produce the following power figures (at the wheels on a Dynojet):

  • 93 octane pump gas: 350–370 whp, 330–350 lb-ft torque
  • E85 fuel: 380–410 whp, 350–370 lb-ft torque
  • Boost levels: 23–26 psi (tapering to redline)
  • Spool characteristics: Full boost by 3,800–4,000 RPM (slightly slower than stock, but maintains boost to redline)

These results represent a 80–120 whp increase over a stock 4B11T, which typically dynos around 260–280 whp. The torque curve is broader than the stock turbo, making the car much more responsive in third and fourth gear pulls. Quarter-mile times improve from the low-mid 13s to high 11s or low 12s with a good driver and traction.

Installation Process in Detail

Understanding what the installation entails can help you decide whether to DIY or pay for labor. Here is a step-by-step outline of the major tasks:

  1. Preparation: Disconnect the battery, drain coolant and oil, remove the under-tray and any intercooler ducting.
  2. Removal of factory components: Unbolt the stock downpipe, remove the intercooler, and disconnect the oil and coolant lines from the turbo. Unbolt the turbo from the exhaust manifold and remove the entire assembly.
  3. Upgrade installation: Transfer any necessary fittings (e.g., banjo bolts) to the new turbo. Attach the new intercooler and piping loosely. Secure the turbo to the manifold with a fresh gasket and tighten in a cross pattern to spec.
  4. Piping and couplers: Connect all silicone hoses and clamps. Ensure no kinks in the intake charge path. Install the turbo inlet pipe and attach the recirculation valve.
  5. Fluids: Refill engine oil and coolant. Prime the oil system by cranking with the fuel pump fuse pulled until oil pressure registers.
  6. Startup and leak check: Start the engine and watch for smoke, oil leaks, or coolant seepage. Check boost pressure by revving gently—listen for unusual whistling (which could indicate a leak).
  7. Initial tune: If using a base tune from APR, the car will run decently. A custom tune should follow within a few drive cycles.

Total time for a skilled mechanic: 6–10 hours. For a first-timer, expect 12–16 hours.

Maintenance and Reliability Considerations

With increased power comes increased maintenance demands. Plan for the following after the upgrade:

  • Oil changes every 2,000–3,000 miles using a high-quality full synthetic 5W-30 or 5W-40 (depending on climate).
  • Spark plugs: Upgrade to a colder range (e.g., NGK LFR7AIX) and replace every 15,000 miles.
  • Boost leak test every 6 months; silicone couplers can dry out or slip over time.
  • Intercooler cleaning annually if you drive in dusty conditions or on track.
  • Fuel system cleaning every 30,000 miles to prevent injector fouling.

The APR Stage 2 turbo itself is built to withstand moderate street abuse, but sustained high boost (above 26 psi) will shorten its lifespan. The journal bearing version may need a rebuild after 40,000–60,000 miles, whereas ball-bearing variants last longer. Plan for a future rebuild costing $300–$500.

Comparison with Other Turbo Upgrades

How does the APR Stage 2 compare to other popular options for the 4B11T?

  • Stock turbo upgrade options (e.g., Evo X standard 16G housing enlargement): Lower cost ($600–$1,200) but limited to 330–350 whp. Less intercooler gain; spool is similar to stock.
  • Garrett GTX3071R or G30-770: More expensive ($2,800–$3,500 for turbo alone) and requires more fabrication. Capable of 450+ whp but sacrifices low-end response. Tuning is more complex.
  • Precision 5858 or 6262: Similar price to APR kit, but no intercooler included. More power potential (450–500 whp) but spools later and requires bigger fuel system.
  • BorgWarner EFR 7670: Excellent spool and power, but cost is higher ($2,200+ for turbo, need separate intercooler). Requires custom downpipe.

The APR Stage 2 strikes a solid balance between cost, ease of installation, and real-world drivability. It’s an ideal choice for someone who wants a reliable 370–400 whp street car without diving into custom fabrication.

Conclusion: Is the $3,500 Budget Realistic?

A strict $3,500 budget covers the APR Stage 2 kit, professional installation, and a base tune—but it does not account for potential fuel system upgrades, exhaust, or cooling improvements. Many owners end up spending closer to $4,500–$5,500 once they factor in necessary supporting mods.

If you already have an upgraded downpipe, intake, and a healthy fuel system, the $3,500 figure is achievable. For a complete build from stock, plan an additional $1,500–$2,000 for fuel and exhaust. With proper planning and execution, the APR Stage 2 system transforms the 4B11T into a responsive, powerful machine that remains reliable for daily driving.

For further reading, consult the APR official website for current pricing and product documentation, and check platform-specific forums like EvolutionM for real-world owner experiences. Many tuners also share dyno graphs and installation tips that can help you budget more accurately.