Mitsubishi 4G18 Tuning

"All you need to know about tuning the Mitsubishi 4G18 Orion engine!"

As many of our readers have asked questions about the 4G18 and recommendations on how to modify one, so we've created this guide to take you through what we feel are the main modifications that make for improvement and tuning success on this great car.

The Mitsubishi 4G18 are fantastic to work on and with carefully picked tuning tuning mods like a remap, turbo upgrades and camshafts you will substantially improve your driving experience.

This pages aim is review 4G18 tuning and summarise the ultimate mods that work.

History of the 4G18 Engine

The 4G orion engine is an inline 4 first introduced in 1977. Much has changed in the world of engines since that release date so there is much that can be done to improve this engine.

110 PS (81 kW) 150 Nm (111 lbft)

The 4G18 was fitted to the following models

  • Mitsubishi Colt Plus (Taiwan)
  • Mitsubishi Kuda
  • Mitsubishi Lancer
  • Mitsubishi Space Star
  • Proton Waja
  • 2005-2010 BYD F3
  • Zotye T600
  • Zotye T700
  • Mitsubishi Lancer (China)

Tuning the Mitsubishi 4G18 and best 4G18 performance parts.

Best 4G18 upgrades

The optimum 4G18 parts on an engine are as we have found the ones that give the best value for money.

We won't be swayed by popular 4G18 parts, they need to be cost effective.

Getting a fast road cam will helps you to boost upper RPM range power which makes it a best mod for NASP and turbo petrol engines, but not so much on diesels. In most cases you will see top end power benefits through performance camshafts on most engines. So altering your 4G18 cam will make a difference to the engine bhp. Choosing a higher performance cam profile raises the torque curve range accordingly.

Fast road camshafts normally boost the power through the rev range, you may lose a little bottom end torque but your higher rpm power will be higher.

Motorsport camshafts, boost the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport and race camshaft makes it harder when on the daily commute.

You should ideally optimize your engines power to your typical driving style so for a road car stick with a mild fast road 4G18 camshaft

Different 4G18 engines respond better to more or less aggressive camshaft durations so view each engine as unique.

The ecu map and injectors and fuel pump also have an effect on the power gains you'll get.

A longer valve duration 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.

Typical stage 1 mods often include: Sports exhaust manifold, drilled & smoothed airbox, Intake headers, Fast road camshaft, Panel air filters, Remaps/piggy back ECU.

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

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

Plan your options and then acquire your mods and set yourself a power target to avoid disappointment.

Remaps helps release the full potential of all the mods you've done to your 4G18.

(Sometimes flashing the ECU 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 around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output often rely on the mods you've fitted and the condition of your engine.

Pushing air and fuel into your 4G18 is the whole point to any performance tuning project.

The intake plenum transmit the air from the intake filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

The bore size, shape and flow rate of the Intake manifold can make a big change to fuel atomisation and engine efficiency on the 4G18.

Most air intake manifolds are in dire need of performance upgrades, although some car makers provide fairly well optimized air intake manifolds.

Adding a 4G18 larger valve kit, getting port work and head flowing will also improve bhp, the fantastic side effect is it will permit a greater bhp increase on other upgrades.

4G18 Turbo upgrades

NASP 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 4G18

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

When an engine has forced induction parts are more reliable and we find turbocharged engines are made with stronger components.

However most engines will have power limits.Discover these limitations and install stronger pistons, crank and engine components to handle the power.

We've seen mechanics spending a loads on turbo charger upgrades on the 4G18 only to have the 4G18 go up in smoke just after it's finished.

Big upgraded turbo chargers commonly suffer low end lag, and smaller turbo chargers spool up really quickly but don't have the peak end bhp gains.

Over the last 20 years the world of turbos is always evolving and we commonly find variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbos divert the exhaust gases into two channels and flow these at differently designed vanes in the turbo charger. They also increase the scavenging effect of the engine.

It is not unusual that there is a limitation in the air flow sensor AFM/MAP on the 4G18 when a lot more air is being drawn into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp and torque at a much lower level.

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


Don't overlook the need to raise the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. We would recommend you to be generous with your injectors flow rate.

As a rule of thumb add 20% when fitting an injector, this allows for injector deterioration and provides you 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
  • 58 PSI 682cc/min 400hp

4 Cylinder NASP engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp
  • 58 PSI 568cc/min 400hp

4 Cylinder supercharged engines

  • 58 PSI 312cc/min 200hp
  • 58 PSI 468cc/min 300hp
  • 58 PSI 625cc/min 400hp

4G18 Performance Exhausts

Only look to replace your exhaust if your current exhaust is actually causing a restriction in flow.

On most factory exhausts you'll find 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.

Don't go with the largest exhaust you can find you'll reduce the exhaust flow rate - the best exhausts for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Usual exhaust restrictions can be located in the catalyst and filters installed, so adding a freer flowing performance aftermarket version is the answer. This keeps the car road legal and will flow much better due to it's higher internal surface area and design, so has the added benefit of keeping your car road legal. The alternative decat should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars.

Weak spots, Issues & problem areas on the 4G18

The 4G18 engines are generally reliable and solid as long as they are regularly serviced and maintained.

Regular oil changes are vital on the 4G18, especially when tuned and will help extend the life and reliability of the engine.

If you want to know more, or just get some friendly advice on Tuning your 4G18 engine please join us in our friendly forum where you can discuss 4G18 tuning options in more detail with our 4G18 owners. It would also be worth reading our unbiased Mitsubishi tuning articles to get insights into each modification and how effective they will be.

Please help us improve these tips by sending us your feedback in the comments box below.

We love to hear what our visitors have got up to and which upgrades work best for them on each model of car. Comments are used to improve the accuracy of these 4G18 articles which are continually updated.

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