Understanding the 4B11T Turbo Upgrade

The 4B11T turbocharger is a standout upgrade for Mitsubishi owners, particularly those with the 4B11T engine found in late-model Lancer Evolutions and other high-performance applications. This turbo is designed to deliver substantial power increases while preserving daily drivability—provided the installation is done with care. The 4B11T itself is a turbocharged, 2.0-liter inline-four that responds well to boost and airflow improvements. Upgrading the turbo on this platform can push output from stock levels (around 290–300 whp) well past 400 whp with proper supporting mods.

Before you commit to the upgrade, it’s critical to understand what you’re getting into. The 4B11T is a twin-scroll design, which means the exhaust housing is split to improve spool and reduce lag. Aftermarket turbo options range from bolt-on direct replacements to larger frame units requiring extensive fabrication. For most owners, a “stage 2” or “stage 3” turbo—often based on the stock housing but with upgraded internals—offers the best balance of power, response, and reliability.

This guide covers the full process: costs, preparation, step-by-step installation, tuning, and common pitfalls. Whether you’re a seasoned fabricator or a first-time installer, working methodically and respecting the hardware will make the difference between a rewarding build and a headache.

Cost Breakdown

Installing a 4B11T turbo upgrade involves more than just the turbo itself. A realistic budget includes the turbo, supporting parts, labor (if not DIY), and post-install tuning. Prices vary by region, brand, and condition (new vs. used), but here’s a typical breakdown:

  • Turbocharger: $1,200 – $2,500 (quality aftermarket units from brands like FP, Garrett, BorgWarner, or MHI). Some “budget” options exist but may lack reliability.
  • Installation Kit: $300 – $800 (gaskets, oil and coolant lines, clamps, bolts, and sometimes an upgraded intake or charge pipe).
  • Labor Costs: $600 – $1,500 (if you pay a shop; DIY saves this, but be honest about your skill level).
  • Tuning: $300 – $700 (depends on software/hardware: Cobb AccessPort, ECUTek, open-source like Evans-Tuning, or dyno time).
  • Additional Supporting Mods (often required): New intercooler ($400–$900), larger MAF/intake ($200–$400), injectors/fuel pump ($300–$600), boost controller ($150–$300).

If you’re starting from a stock engine, expect the total to land between $2,500 and $5,000 for a well-done, reliable setup. Skipping parts (like gaskets or proper tuning) to save money usually costs more in the long run.

Preparation Steps

Preparation is the key to a smooth installation. Rushing leads to stripped bolts, leaks, and frustration. Gather everything before you start.

Tools You’ll Need

  • Metric socket set (deep and shallow), including extensions and a universal joint
  • Torque wrench (ft-lb and in-lb range)
  • Pry bars, screwdrivers (flathead and Phillips), pliers
  • Oil pan and coolant drain pan
  • Shop rags, degreaser, penetrating oil (e.g., Kroil, PB Blaster)
  • Jack and jack stands or lift
  • Safety glasses, gloves, fire extinguisher

Parts and Consumables

  • New turbocharger (preferably with all necessary fittings and flanges)
  • Complete gasket set: T3/T4 flange gasket, exhaust manifold gasket, downpipe gasket, oil drain gasket
  • New oil feed and return lines (stainless braided recommended)
  • Coolant lines (if applicable for water-cooled turbos)
  • Fresh engine oil and filter
  • New coolant (appropriate type for your climate)
  • Threadlocker (medium strength) for critical bolts
  • Anti-seize compound for bolts that come into contact with exhaust heat

Workspace and Safety

Work in a well-ventilated, clean area. Disconnect the battery before starting. Let the engine cool completely—exhaust components retain heat for hours. Have a plan for dealing with spilled oil and coolant.

Installation Steps

These steps assume you’re replacing the factory turbo with an upgraded aftermarket unit using a similar mounting pattern. Variations exist depending on the turbo kit, so always cross-reference with the manufacturer’s instructions.

  1. Disconnect battery and drain fluids. Remove negative terminal. Drain coolant and engine oil into clean containers (you may reuse the oil if it’s fresh, but replace the filter).
  2. Remove air intake system. Unbolt the intake pipe, airbox, and MAF sensor. Cover the intake manifold opening with a rag.
  3. Disconnect exhaust. Unbolt the downpipe from the turbo. Support the exhaust with a jack or strap to avoid stress on remaining hangers.
  4. Remove intake manifold (if necessary). On many 4B11T setups, the intake manifold must come off to access turbo-to-intercooler piping and oil/coolant lines. Label all vacuum lines and connectors.
  5. Detach oil and coolant lines. Use a flare nut wrench on the oil feed line at the turbo and block. Have a rag handy for residual oil. Similarly, disconnect coolant lines at the turbo.
  6. Unbolt the turbo. The turbo is usually held by three or four nuts on the exhaust manifold studs. A swivel socket helps. Also unbolt the turbo support bracket if equipped.
  7. Remove the old turbo. Wiggle it free from the manifold. Watch for gasket fragments and clean the mating surface thoroughly.
  8. Prepare the new turbo. Before mounting, check that the wastegate actuator arm moves freely. Install the oil feed fitting (use thread sealer on the block side). Pre-lube the turbine bearings with a small amount of clean engine oil.
  9. Install new turbo. Use a new gasket on the manifold flange. Tighten the mounting nuts evenly to torque specs (typically 35–45 ft-lb, but verify per turbo brand). Reattach the support bracket.
  10. Reconnect oil and coolant lines. Use new washers where required. For the oil return line, ensure it slopes downward to the block—no dips that trap oil.
  11. Reattach intake manifold and piping. Install new gaskets on intake manifold and throttle body. Torque to spec in a crisscross pattern.
  12. Reconnect downpipe and exhaust. Tighten downpipe bolts to 30–40 ft-lb. Double-check for clearance against the engine block and chassis.
  13. Reconnect battery, refill oil and coolant. Use the correct oil weight (usually 5W-30 or 5W-40). Fill coolant slowly to burp air from the system.
  14. Prime the turbo. Crank the engine with the fuel pump fuse disconnected (or disable injectors) for about 15 seconds to circulate oil before firing. Then reconnect and start the engine.
  15. Check for leaks. Let the engine idle and inspect all connections. Rev gently to test for exhaust leaks. Correct any issues immediately.

Tuning the Engine

You cannot simply bolt on a bigger turbo and drive off. The ECU must be reprogrammed to account for increased airflow, fuel needs, and boost targets. Here’s what that involves:

ECU Options

  • Cobb AccessPort V3: User-friendly, with pre-loaded maps for common turbo upgrades. Requires a professional tune for best results.
  • ECUTek: More advanced, allows full control. Used by many high-performance tuners. Requires a dongle and license.
  • Open source (Tactrix cable & RomRaider/Evans-Tuning): Budget-friendly but requires significant self-education.

Tuning Goals

  • Target air-fuel ratio: 11.5–12.0:1 under full boost for safety.
  • Boost level: typical for mid-range turbos is 20–24 psi on pump gas (93 octane). Higher requires ethanol or race fuel.
  • Ignition timing: dialed back to prevent detonation.

Recommended: Find a reputable tuner with experience on the 4B11 platform. A poor tune can destroy the engine in minutes. Expect 1–3 hours of dyno time at $100–$200 per hour, or a few hours of street tuning if the tuner is experienced.

Common Challenges and Solutions

Every turbo upgrade has its stubborn moments. Here are the most frequent problems and how to handle them.

  • Stuck exhaust manifold bolts/nuts. Apply penetrating oil hours before. Use a six-point socket and heat if accessible. If a stud breaks, drill and extract—or replace with a timesert.
  • Oil feed line leaks. Often caused by using the wrong banjo bolt crush washers or over-tightening. Always use new OEM or proper copper/aluminum washers. Torque the banjo bolt to spec (around 25 ft-lb).
  • Boost creep / boost spike. Caused by an undersized wastegate or blocked port. Solutions: upgrade to a larger wastegate (external if using an open-dump setup), or port the wastegate hole on the turbo housing. A boost controller (electronic recommended) helps manage spikes.
  • Coolant leaks at turbo water fittings. Ensure the O-rings are intact and seated. Do not over-tighten—the fittings can crack.
  • Intercooler piping not fitting. Aftermarket kits sometimes require trimming. Measure twice, cut once. Use silicone couplers and T-bolt clamps for security.
  • Overheating at idle. If you removed the factory turbo heat shield, consider wrapping the downpipe or installing a new shield. Also ensure the coolant system is fully bled.

Final Tips for a Smooth Upgrade

These extra pointers come from experienced builders and will save you time and money.

  • Replace all gaskets and seals wherever you unbolt something. Gaskets are cheap; leaks are not.
  • Use a turbo timer or let the engine idle for 1–2 minutes after hard driving to cool the turbo bearings before shutdown. This extends turbo life.
  • Check for wheel well clearance if your car is lowered. Potholes can damage a low-hanging downpipe.
  • Don’t skimp on the tune. The most reliable 500 whp cars have excellent tunes; the blown-up 300 whp cars usually had bad tunes.
  • Join community forums like EvoM (evolutionm.net) or the 4B11T Facebook groups. You’ll find model-specific write-ups and troubleshooting.
  • Consider a compression and leak-down test before installation. No point upgrading a tired engine—ensure it’s healthy to handle the extra power.

For further reading, check out Cobb Tuning’s 4B11 guides and the technical resources at EvolutionM.net. For parts sourcing, MAPerformance offers verified turbo kits.

Conclusion

Installing a 4B11T turbo upgrade is a rewarding project that transforms the character of your Mitsubishi. It demands patience, proper tools, and a commitment to detail—especially during tuning. By following the cost breakdown, preparation steps, and installation sequence outlined here, you can avoid the most common pitfalls and enjoy a reliable, powerful upgrade. Respect the hardware, invest in a professional tune, and your car will reward you with thrilling performance for many miles.