Mitsubishi 4J1x Tuning (4J10 4J11 4J12)

"All you need to know about tuning the Mitsubishi 4J1 engine!"

The Mitsubishi 4J1 is a range of all-aluminum straight-4 internal combustion engines, designed and produced by Mitsubishi Motors.

I have to say there are few mods & upgrades around that I have found for this little beauty, so please use the comments below to pass on tips & suggestions to help me make this article less general and much more comprehensive and useful, and thank you to all the people who have already passed on tips.

The primary goal of the 4J1 engine designers was to reduce on-road CO2 emissions. The 4J1 engine was first introduced in 2011 and is currently in production.

The 4J1 engine is available in three displacements: 1.8 L (1,798 cc), 2.0 L (1,997 cc), and 2.4 L (2,359 cc). All 4J1 engines are water-cooled and have an aluminum die-cast cylinder block. The 1.8 L and 2.0 L engines have a compression ratio of 10.5:1, while the 2.4 L engine has a compression ratio of 10.7:1.

The 4J1 engine uses Mitsubishi's MIVEC variable valve timing system, which helps to improve fuel economy and reduce emissions. The MIVEC system continuously regulates intake valve lift, opening duration, and timing. The 4J1 engine also features improved combustion stability and reduced piston friction, which further contributes to its fuel efficiency.

The 4J1 engine is used in a variety of Mitsubishi vehicles, including the Lancer, Outlander, and RVR. It has been praised for its smooth operation, quietness, and fuel efficiency.

But the question we have to look at here is how to improve performance and gain power from this engine with mods & upgrades?

Here we review and look at 4J1 tuning and report on the premier modifications for your car. Mitsubishi 4J1 provide a fun base for your project and with the optimum performance parts like remaps, turbo improvements and camshafts you will really maximise your driving experience.

History, Power & Specs of the 4J1 Engine

Here are some of the specifications of the Mitsubishi 4J1x engine:

Engine type: All-aluminum Inline 4-cylinder SOHC 16v, MIVEC

Displacements: 1.8 L (1,798 cc), 2.0 L (1,997 cc), and 2.4 L (2,359 cc)
Compression ratio: 10.5:1-10.7:1
Cylinder bore: 86 mm (3.39 in); 88 mm (3.46 in)
Stroke: 88 mm (3.46 in)


102 kW (139 PS) at 6000 rpm 172 Nm (127 lbft) at 4200 rpm

  • 2013 Mitsubishi RVR (Japan)
  • 2017 Mitsubishi Grand Lancer (Taiwan)


110 kW (150 PS) at 6000 rpm 195 Nm (144 lbft) at 4100-4200 rpm

  • 2013-2016 Mitsubishi Outlander
  • 2020- Mitsubishi ASX


124 kW (169 PS) at 6000 rpm 220 Nm (162 lbft) at 4200 rpm

  • 2016 Mitsubishi Outlander (Only vehicles for South Africa and Argentina)
  • 2016 - present Mitsubishi Outlander (ES, SE, SEL Trims in United States and Puerto Rico)
  • 2013 - 2017 Mitsubishi Outlander (Australia)

Tuning the Mitsubishi 4J1 and best 4J1 performance parts.

Best 4J1 upgrades

Just because particular upgrades are are common on 4J1 it doesn't mean you should fit it, instead we'll best upgrades that will give your 4J1 the best power gain for you money.

MIVEC does a good job on the camshaft durations so getting the MIVEC to kick in earlier down the RPM range can provide a little more top end power. This will be at the expense of fuel economy and I have to note that permanently kicking in MIVEC would be detrimental to low RPM power particularly smoothness.

For a car used daily you need to match your torque band to your driving style.

If you are developing a track car this doesn't matter as you are in the high end of your RPM range anyway and that is where you want the power to be and your aim is to make the engine respond more quickly to rev changes.

Lighter flywheels

Advantages of a Lighter Flywheel:

Improved Throttle Response: A lighter flywheel reduces rotational inertia, allowing the engine to respond more quickly to changes in throttle input. This leads to a more immediate and responsive acceleration.

With less mass to rotate, the engine can rev up and down more rapidly. This is especially beneficial in situations where quick throttle changes are required, such as during gear shifts.

The reduced rotational inertia makes engine braking more efficient, contributing to better control when decelerating.

The engine can transfer power to the wheels more efficiently, resulting in quicker acceleration times.

Improved Gear Changes: Lighter flywheels make it easier to synchronize engine speed with the transmission during gear changes, promoting smoother shifts.

Disadvantages of a Lighter Flywheel:

Reduced Smoothness at Low RPM: Lighter flywheels can lead to a less smooth idle and low-speed operation. The engine may be more prone to stalling in certain situations.

Inertia helps maintain engine speed, and a significantly lighter flywheel may result in a loss of momentum, making it challenging to crawl or maintain a constant speed at low RPM.

Potential for Increased NVH (Noise, Vibration, Harshness): Some drivers may notice an increase in engine and transmission noise, as well as vibrations, especially at lower speeds.

Lighter flywheels can make it more challenging to modulate the clutch during takeoff, as the reduced mass may result in a quicker engagement.

Drivers accustomed to the feel of a heavier flywheel may need time to adjust to the different driving characteristics of a lighter flywheel.

The ECU mapping and fuelling also have a large bearing on the power gains you'll hit.

Altering valve durations can alter the power band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

Please watch our video which covers the 5 principles of tuning your car. Be sure to keep up with our latest YouTube content and subscribe.

Best Engine Mods for your car

    1. Engine Tunes - engine tuning/remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
    2. Lighter flywheels - help the engine rev more freely and feels more responsive.
    3. Intake and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
    4. Upgrades to turbochargers and superchargers - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.
    5. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.

Typical stage 1 mods often include:
Panel air filters, Sports exhaust header/manifold, Lighter flywheel, Intake manifolds, drilled & smoothed airbox, Lower MIVEC point, Remaps/piggy back ECU.

Typical stage 2 mods often include:
fuel pump upgrades, high flow fuel injectors, Ported and polished head, induction kit, Sports catalyst & performance exhaust.

Typical stage 3 mods often include:
Internal engine upgrades (head flowing porting/bigger valves), Competition cam, Crank and Piston upgrades to alter compression, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Twin charging conversions.

The 4J1 power plant respond well to mods and thankfully there are plenty of mods and tuning parts around.

ECU mapping allows a tuner to release the full potential of all the parts you've done to your 4J1.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 15% on NA (naturally aspirated) engines, but the outcome usually rely on the parts you've applied and the condition of your engine. The primary goal for most is to adjust the MIVEC points.

It is the whole point to any engine modification project to force more air and fuel into the 4J1 engine

Air Intake manifolds transmit the air from the air filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

The shape and flow rate of the Intake manifolds can make a noticeable difference to fuel atomisation and engine efficiency on the 4J1.

On popular production engines air intake manifolds are crying out for aftermarket parts, although a few car makers provide fairly well optimized air intake manifolds.

Increasing the 4J1 valve size, carrying out port matching and head flowing will also lift performance, & more importantly will make space for raising the performance increase on other tuning mods.

4J1 Turbo upgrades

NA (naturally aspirated) engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your 4J1

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes major power gains.

When your motor has a turbo already fitted upgrades are relatively easy and we find turbo engines are made using strengthened components.

However engines have weakspots.It is important to find these limitations and install better quality components to survive the power.

We've seen car owners spending a lot of money on turbo upgrades on the 4J1 only to suffer the humiliation of seeing the engine explode soon after it's been completed.

Large upgraded turbo units tend to experience low end lag, and little turbo units spool up much more quickly but won't have the high rpm bhp gains.

Over the last 20 years the choice of turbo units is always increasing and we now see variable vane turbo units, allowing the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbo units divert the exhaust flow into 2 channels and flow these at differently profiled vanes in the turbo. They also improve the scavenging effect of the engine.

You'll commonly see there's a restriction in the air flow sensor MAP/MAF/AFM on the 4J1 when loads more air is being drawn into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited performance at a much lower level.

Adding a supercharger or additional turbo will make large performance gains, although more difficult to configure. We have this feature on twinchargers if you want to read more.


Don't forget to improve the fuelling when you are increasing the performance - it makes the car more thirsty. It makes sense to over specify your flow rate on the injectors.

The rule of thumb is to add 20% to the flow rate when specifying an injector, which takes into account injector deterioration and allows some spare capacity should the engine require more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder turbocharged engines

      • 58 PSI 340cc/min 200hp
      • 58 PSI 511cc/min 300hp

4 Cylinder NA (naturally aspirated) engines

      • 58 PSI 285cc/min 200hp
      • 58 PSI 426cc/min 300hp

4 Cylinder supercharged engines

      • 58 PSI 312cc/min 200hp
      • 58 PSI 468cc/min 300hp

4J1 Performance Exhausts

You should look to increase your exhaust if the existing exhaust is actually causing a flow problem.

On most factory exhausts you should find that your flow rate is still fine even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Sports exhausts can usually air flow out of the engine but do not go too wide or you might just stuff your flow rate and make things worse. So generally speaking, keep to a size of 1.5 to 2.5 inches for best results.

Typically exhaust restrictions can be traced to the filters installed, so adding a freer flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots, Issues & problem areas on the 4J1

The 4J1 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Oil consumption:

The 4J10 engine is known to consume excessive amounts of oil, especially in high-mileage vehicles. This is often due to worn piston rings or valve seals.

Engine knocking:

The 4J10 engine can also develop a knocking noise, which is often caused by detonation. Detonation occurs when the air/fuel mixture in the engine ignites too early, causing a rapid pressure spike that can damage the engine.

Timing chain problems:

The 4J10 engine uses a timing chain to drive the camshafts. Over time, the timing chain can stretch or wear, which can cause the engine to run erratically or lose power. In some cases, the timing chain can even break, which can cause serious engine damage.

Coolant leaks:

The 4J10 engine is also prone to coolant leaks. These leaks can occur from a variety of places, including the water pump, radiator, and hoses.

Electrical problems:

The 4J10 engine can also experience electrical problems, such as alternator failure, battery problems, and wiring issues.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the 4J1, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your 4J1 engine please join us in our car forums where you can discuss 4J1 tuning options in more detail with our 4J1 owners. It would also be worth reading our unbiased Mitsubishi tuning articles to get insights into each modification and how effective they will be for your car.

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We love to hear what our visitors have got up to and which modifications work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these 4J1 tuning guides which get regular updates and revisions.

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