Best 4b11t Power Gains: How Upgrading to a Garrett Gtx Spec Can Add 80hp
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The 4B11T engine, a turbocharged 2.0-liter inline-four, powers some of Mitsubishi's most iconic performance vehicles. While already potent from the factory, aftermarket turbocharger upgrades offer substantial headroom. Among the most popular and effective options is the Garrett GTX series. This article details how upgrading to a Garrett GTX turbo can unlock up to 80 additional horsepower and explains the supporting modifications required to achieve and maximize these gains.
The 4B11T Engine: A Closer Look
First introduced in the Mitsubishi Lancer Evolution X, the 4B11T features an aluminum block and cylinder head, MIVEC variable valve timing, and a twin-scroll Mitsubishi TF03HL turbocharger from the factory. Key specifications include:
Displacement: 1998 cc (2.0L)
Bore & Stroke: 86 mm x 86 mm
Compression Ratio: 9.0:1
Factory Boost: ~20 psi (peak)
Factory Output: 291 hp (Evo X) — varies by market
The 4B11T’s closed-deck design and strong bottom end make it capable of handling 500+ horsepower with proper fueling and tuning. However, the stock turbocharger becomes a bottleneck above about 350–400 wheel horsepower due to its limited compressor flow and restrictive turbine housing.
Why Upgrade from the Stock Turbo?
The factory TF03HL turbo spools quickly but runs out of steam in the upper rev range. If you’re chasing more than 400 whp for track days, drag racing, or spirited street driving, a larger aftermarket turbo is necessary. Upgrading to a Garrett GTX unit addresses three core weaknesses:
Insufficient compressor flow — at higher boost levels, the stock turbo generates excessive heat and backpressure.
Poor thermal efficiency — the factory unit’s cast wheels create turbulence and reduce efficiency at high airflow.
Limited turbine flow — the stock turbine housing restricts exhaust gas flow, limiting top-end power.
By replacing the turbo with a modern GTX series, you remove these constraints while maintaining a broad powerband.
Garrett GTX Series Overview
Garrett's GTX line uses billet compressor wheels, aerodynamically optimized turbine designs, and advanced bearing systems. Two popular choices for the 4B11T are the GTX2860R and the GTX3076R. Both deliver significant airflow improvements.
Turbo Model
Compressor Inducer/Exducer
Max Flow (lb/min)
Typical HP Range (4B11T)
Spool Characteristic
GTX2860R Gen II
53.8 / 71.4 mm
45
350–450 whp
Fast spool, OEM+ response
GTX3076R Gen II
60.5 / 76.4 mm
65
450–600 whp
Slightly laggy, huge top-end
The GTX2860R is a popular drop-in replacement for those who want an extra 80–100 hp without major fabrication. The GTX3076R is for a full-race setup, offering gains of 150+ hp but requiring injectors, fuel pump, and a custom downpipe.
How the Upgrade Adds 80 Horsepower
A direct comparison between a stock 4B11T running 20 psi and the same engine with a GTX2860R at 22 psi shows a peak increase of roughly 80–90 wheel horsepower. The gain comes from three factors:
Higher mass airflow: The GTX compressor moves more air per revolution, allowing the engine to burn more fuel.
Better charge temperature: The billet wheel’s aero design reduces outlet temperatures by 10–20°F at the same boost, increasing air density.
Reduced backpressure: The GTX turbine flows exhaust gas more freely, lowering cylinder pressures and allowing the engine to breathe at high RPM.
On a mustang dyno, a 4B11T with stock ECU, minimal supporting mods, and a Garrett GTX2860R typically sees a jump from 280–300 whp to 360–380 whp — right in that 80 hp range. With a proper tune, cat-back exhaust, and a front-mount intercooler, 400 whp is common.
Supporting Modifications to Maximize Gains
Installing a Garrett GTX turbo alone won’t yield 80 hp if the rest of the system is restrictive. Here are the essential supporting modifications:
Fuel System Upgrades
The stock fuel pump and injectors run out of capacity around 350 whp. For a GTX setup, install:
High-flow fuel pump: Walbro 255 lph or AEM 340 lph
Larger injectors: 750–1000 cc/min (EVO 14 injectors or FIC units)
Boost reference fuel pressure regulator (FPR): optional but recommended for consistent fueling
Intercooling and Intake
A larger front-mount intercooler (Mishimoto, AMS, or ETS) reduces charge air temperatures under sustained boost. Pair with a 3-4” cold air intake and smooth inlet tube to minimize restriction.
Exhaust System
The stock downpipe and cat-back are restrictive above 300 whp. A 3-inch turbo-back exhaust (with high-flow cat or test pipe) is mandatory. The downpipe should match the GTX turbine outlet (typically a T25 flange for the GTX2860R; T3 flange for GTX3076R).
Engine Management & Tuning
The factory ECU cannot handle the fuel and airflow changes of a GTX turbo without reprogramming. Options include:
ECU flash (Cobb AccessPort, EcuTek, or open source) — most common for 2008+ Evos
Standalone ECU (Haltech, AEM, Motec) — for high-horsepower builds with flex-fuel or anti-lag
A professional tuner will dial in fuel maps, ignition timing, boost control duty cycles, and MAF or MAP scaling. Expect to pay $400–$800 for a dyno tune.
Installation Considerations
Installing a Garrett GTX turbo on a 4B11T is not a beginner-level job. You’ll need to remove the stock exhaust manifold, downpipe, oil lines, and coolant lines. Here’s an overview of the process:
Disconnect battery and drain coolant/oil.
Remove turbo assembly — unbolt the manifold from the head, disconnect the O2 sensor, and slide the turbo out.
Swap the oil and coolant lines — use AN fittings for reliability; avoid crush washers on the banjo bolts.
Install the GTX turbo with gaskets — torque to factory specs (manifold to turbo: 35 ft-lbs; turbo to downpipe: 40 ft-lbs).
Reconnect lines and fill coolant/oil.
Reinstall intake, intercooler piping, and downpipe.
Prime the turbo by cranking the engine with the fuel pump relay disconnected (5–10 seconds of cranking) to circulate oil.
Start engine and check for leaks; then drive gently for 50 miles before hitting full boost.
Total: roughly $3,600–$5,400 for a reliable 400 whp setup. That’s about $45–$68 per horsepower gained — an excellent value compared to building a fully forged engine. The gain is not just peak power; mid-range torque improves by 50–70 lb-ft from 3500–5500 RPM, making the car feel faster everywhere.
Real-World Results: Dyno Charts & Testimonials
Many 4B11T owners have documented their GTX upgrades on forums like EvoM and Mitsubishi Lancer Register. One well-known example is a 2008 Evo X with:
Garrett GTX2860R
3” turbo-back exhaust
ETS intercooler + hard-pipe kit
Walbro 255 fuel pump, 1000 cc injectors
Cobb AccessPort with a pro tune on 93 octane
This car laid down 397 whp and 366 lb-ft (see the dyno chart on EvolutionM). That’s 97 hp over bone stock. With ethanol (E85), the same turbo can push 440–460 whp.
A second example from a UK tuner paired the GTX3076R with a fully built head and cams, producing 560 whp on pump gas. While 80 hp is conservative for a GTX upgrade, it’s a reliable, repeatable number for a street-driven car that retains daily drivability.
Frequently Asked Questions
Can I keep my stock intercooler with a GTX turbo?
Technically yes, but charge temperatures will rise quickly. We strongly recommend upgrading to a more efficient core that supports 400+ hp.
Do I need to upgrade my clutch or transmission?
At 400 whp, the stock SST or 5-speed manual can hold up if not abused. For launches or high- boost drag runs, a stronger clutch and upgraded transfer case are wise.
Will a GTX turbo pass emissions?
That depends on your location and the turbo size. The GTX2860R retains a catalytic converter (with a high-flow unit) and can pass sniffer tests with proper tuning. Larger units often force removal of the cat.
Conclusion
Upgrading your 4B11T to a Garrett GTX turbo is one of the most effective bolt-on modifications you can perform. With gains of 80-plus horsepower from a well-chosen model like the GTX2860R, you transform the driving experience without sacrificing daily reliability. The key to success lies in pairing the turbo with suitable supporting mods and a professional tune. Whether you’re building a weekend track car or a street sleeper, the GTX series delivers a proven power increase that justifies the investment.