The Mitsubishi Lancer Evolution X's 4B11T engine is a legendary turbocharged inline-four that offers exceptional tuning potential for enthusiasts seeking real power gains. While the stock turbo and fueling system limit this engine to around 300–350 horsepower on pump gas, reaching the 400‑plus horsepower mark is not only achievable but can be done without breaking the bank when you select the right components. In this guide, we’ll break down a proven, cost‑effective upgrade path using parts from market leaders Turbosmart, HKS, and Precision Turbo, covering everything from the turbocharger and fuel system to engine management and supporting mods.

Understanding the 4B11T Engine: Strengths and Bottlenecks

The 4B11T is a 2.0‑liter, DOHC, 16‑valve engine featuring MIVEC (Mitsubishi Innovative Valve timing and lift Electronic Control) on both intake and exhaust cams. It comes factory‑equipped with a twin‑scroll Mitsubishi TD05HRA turbocharger and an air‑to‑air intercooler. The closed‑deck cast‑iron block and forged crank are stout enough to handle well over 400 horsepower with proper tuning, but several factory components become limiting as you push past the 350‑hp threshold:

  • Factory turbocharger – The TD05HRA runs out of airflow around 350–380 whp.
  • Fuel system – Stock injectors (560cc) and fuel pump reach their duty cycle limit around 370 bhp.
  • Intake and exhaust – Restrictive intake tract and exhaust system create pressure drop and heat soak.
  • Engine management – Factory ECU has limited tuning flexibility without reflash or standalone.

Addressing these bottlenecks with targeted upgrades from Turbosmart, HKS, and Precision Turbo will unlock the 400+ hp figure you’re after.

Key Upgrades for Achieving 400+ HP on the 4B11T

1. Turbocharger Upgrade – Precision Turbo

The single most effective modification for substantial power gain is a larger turbocharger. Precision Turbo offers bolt‑on and near‑bolt‑on options that are well suited for the 4B11T’s spool characteristics and airflow requirements:

  • Precision Turbo PT5858 GEN2 – A direct bolt‑on replacement for the stock frame. Supports up to roughly 500 hp with excellent response. Ideal for a street‑focused 400‑hp build.
  • Precision Turbo PT6266 GEN2 – Slightly larger, capable of 600+ hp. Requires minor modifications to the compressor cover and inlet piping but delivers top‑end power that easily exceeds 400 whp.

Both turbos use a journal bearing or optional ball bearing center section, and they pair well with a quality wastegate and blow‑off valve (discussed below). For a reliable 400‑hp setup, the PT5858 is the sweet spot: it spools quickly and keeps the power band usable on the street.

2. Fuel System Upgrades – HKS

To support the increased airflow from a larger turbo, you need sufficient fuel delivery. HKS is well known for its precision fuel components that are direct replacements or easy upgrades for the Evo X:

  • HKS 850cc Injectors – Drop‑in injectors that provide 50% more flow than stock. They are built for high‑ethanol fuel blends (E85) if desired.
  • HKS Fuel Pump Upgrade (265 LPH) – A plug‑and‑play high‑flow pump that keeps up with the injectors’ demands. It fits inside the factory fuel hanger.
  • Optional: HKS Fuel Pressure Regulator – If you run aftermarket fuel rails or high boost, an adjustable regulator helps maintain consistent pressure.

With these components (and proper tuning), the fuel system will comfortably support 450+ hp on pump gas or E85.

3. Engine Management and Tuning

Overseeing all the new hardware is the engine management system. A quality tune is mandatory to safely achieve 400+ hp while maintaining drivability and reliability. Two popular choices are:

  • ECUtek Tune – Works with the factory ECU via a reflash or Race ROM. Allows adjustment of fuel maps, ignition timing, boost control, and more. Many tuners offer off‑the‑shelf maps for the Precision Turbo + HKS combination.
  • AEM Infinity Series ECU – A full standalone unit that gives complete control over every parameter, including dual closed‑loop boost control, flex‑fuel capability, and advanced datalogging. AEM Infinity is ideal if you plan further upgrades later.

Whichever system you choose, work with a tuner experienced on the 4B11T platform. A solid tune not only extracts power but also protects your engine from detonation.

4. Boost Control and Blow‑Off Valve – Turbosmart

To manage the higher boost levels (typically 22–26 psi for 400 hp), you need a reliable boost control system and a blow‑off valve (BOV) that handles the flow without leaking. Turbosmart’s products are engineered for high‑boost, high‑flow applications:

  • Turbosmart IWG75 Wastegate – Direct replacement for the factory internal wastegate actuator. Stronger spring pressure prevents boost creep and gives consistent control.
  • Turbosmart Kompact EM BOV – A compact, plumb‑back blow‑off valve that vents excess pressure without causing rich‑on‑lift conditions. It’s fully serviceable and adjustable.
  • Turbosmart e‑Boost2 Controller – An electronic boost controller that lets you dial in boost levels from inside the cabin. Essential for tuning multiple boost maps (e.g., low boost for daily driving, high boost for track).

These components ensure the turbocharger operates efficiently and the throttle response remains crisp.

5. Intercooler Upgrade – Turbosmart / HKS

Higher boost and airflow generate more heat. A larger, more efficient intercooler reduces intake air temperatures (IATs), which is critical for preventing knock and maintaining consistent power. Two excellent options:

  • Turbosmart Front Mount Intercooler (FMIC) Kit – Designed to replace the factory side‑mount or top‑mount intercooler on the Lancer Evolution X. Includes cast end tanks and a bar‑and‑plate core that flows better and cools significantly.
  • HKS Intercooler Kit – A step‑up in size and efficiency, featuring a tapered core that optimizes airflow through the factory bumper opening. Ideal if you plan to run over 400 hp.

Pair your intercooler with upgraded charge piping from Turbosmart to eliminate any restrictive factory rubber hoses.

6. Exhaust System Upgrade – Turbosmart / HKS

A free‑flowing exhaust system reduces backpressure and helps the turbo spool faster. It also drops IATs under the hood. For a 400‑hp build, you want at least a 3‑inch turboback exhaust:

  • Turbosmart Exhaust System – Offers a full 3‑inch system with a high‑flow catalytic converter (optional) and a resonated midpipe for noise control. The mandrel‑bent tubing minimizes restriction.
  • HKS Hi‑Power Exhaust – A well‑known system that uses a straight‑through muffler design. It’s lightweight and produces a deep tone without being obnoxious.

Don’t forget to upgrade the downpipe and test pipe (if legal) – the factory downpipe is a major bottleneck.

7. Intake and Induction – HKS / Turbosmart

Getting cool, dense air into the turbo is essential. The factory airbox and intake tract are restrictive. Upgrade options:

  • HKS Racing Suction Intake Kit – A cone‑style filter with a heat shield that mounts directly to the compressor inlet. Provides a noticeable increase in turbo spool sound and lower pressure drop.
  • Turbosmart Intake Pipe – Replaces the rubber intake elbow with a smooth aluminium mandrel‑bent pipe, eliminating flex under high boost.

Combined with a larger intercooler, these mods will drop IATs and improve throttle response.

Supporting Mods for Reliability at 400+ HP

While the core upgrades above will get you to 400+ hp, a few additional parts ensure your 4B11T stays together under sustained load:

  • Clutch Upgrade – The stock clutch slips around 350 whp. An aftermarket unit such as the HKS Clutch Kit (Launche Control) or a twin‑disc from South Bend Clutch is necessary.
  • Valvetrain – stock valve springs and retainers are okay to around 7500 rpm. For higher revs (8000+), upgrade to HKS Valve Springs and Retainers to prevent valve float.
  • Oil System – A baffled oil pan and an upgraded oil pump (or oil cooler) are recommended for track use. High‑power builds generate more heat and stress.
  • Upgraded Motor Mounts – Stiffer mounts from Turbosmart or HKS reduce wheel hop and protect the drivetrain from shock loads.

Installation and Tuning: Putting It All Together

Once you have sourced all the upgrades from Turbosmart, HKS, and Precision Turbo, professional installation is strongly advised. The 4B11T engine bay is tight, and proper torque specs, wiring, and plumbing are critical. After installation, the car must go to a tuner with a dyno. Expect to spend a session dialing in fuel and ignition maps, boost curves, and knock control. A typical 400‑hp dyno tune using ECUtek or AEM will take a few hours, and many tuners offer remote tuning support if you have the right hardware.

Conclusion

Reaching 400+ horsepower on your 4B11T engine is a realistic goal when you follow a well‑planned upgrade path. By focusing on a quality turbocharger, a capable fuel system, robust boost control, and a proper tune – all using proven components from Turbosmart, HKS, and Precision Turbo – you’ll build a reliable, daily‑driveable Evolution X that punches far above its weight. For more details on specific products, visit the official websites or consult a dedicated Evo X tuning forum.