Modding upgrading and tuning the Mitsubishi 4G9 engine!

The Lowdown on "4G9 Modifications"

How to modify and upgrade the Mitsubishi 4G9

"Comprehensive guide to tuning the Mitsubishi 4G9 engine!"

TorqueCars are frequently getting posts asking how to improve the 4G9 from people inquiring about getting more power from the 4G9 and wanting to know what are the premier 4G9 upgrades. So let us look into Mitsubishi 4G9 mods and outline the best mods that work on this great engine and point out some problems along the way.

We shall detail the best approach to 4G9 tuning and provide tips on the best modifications for your car. Mitsubishi 4G9 provide a fun base for your project and with a few sensible motorsport tuning mods like ECU maps, turbo kits and camshafts you will maximize your driving experience.

The optimum 4G9 mods on an engine are typically the ones that give the best gains for your money.

We won't be swayed by popular 4G9 mods, they need to be cost effective.

4G9 induction kits

Improving air intake on the 4G9

You need fuel and air for an engine to work. If there is not enough fuel then it will run lean, if there is not enough air it runs rich resulting in lost power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Pulling fuel and air into the 4G9 engine is the primary aim to any performance tuning task.

It is common that there is a restriction in the air flow sensor (AFM/MAF/MAP) on the 4G9 when considerably more air is being pulled into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp and torque at a much lower level.

Headers transmit the air from the filter and allow it to be sucked into the engine and mixed with fuel.

The bore size, shape and flow characteristics of the Air Intake manifolds can make a big change to fuel atomisation on the 4G9.

On popular production engines intake are needing an upgrade, although some car makers provide fairly well optimized intake.

Larger 4G9 valves, carrying out port matching and head flowing will also lift bhp, & importantly will make space for raising the bhp increase on other tuning mods.

4G9 performance cam tips.

Different 4G9 engines respond better to extreme camshaft durations than others.

The engine timing and injectors and fuel pump also have a large bearing on the bhp gains you'll achieve.

Altering valve durations can alter the bhp 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.

Altering your 4G9 camshaft will make a dramatic difference to the engine bhp. Choosing a higher performance camshaft profile raises the bhp accordingly.

NB: Fast road camshafts usually bump the bhp and torque over the rpm range, you may sacrifice a little low down torque but the top end will be better.

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

For a daily driver you should ideally to optimize your bhp range to your driving style.

I'd be surprised if you find a 4G9 Competition camshaft is a pleasure to live with when driving around busy urban areas.

Stage 1, 2 and 3 mods for the 4G9

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 4G9 parts:

Sports exhaust manifold, Drilled & smoothed airbox, Remaps/piggy back ECU, Fast road camshaft, Panel air filters, Intake headers.

Stage 2 4G9 parts:

high flow fuel injectors, fuel pump upgrades, Fast road cam, Sports catalyst & performance exhaust, Ported and polished head, induction kit.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 3 4G9 parts:

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

Plan your options and then buy your tuning parts and set yourself a power target to avoid wasting your time and money.

A remap will help fully realize the full potential of all the mods you've done to your 4G9.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome usually rely on the mods you've done and the condition of your engine.

Turbo modifications on the 4G9

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 4G9.

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

When the engine is fitted with a turbo parts are going to make more power and most turbo engines are made with many forged and stronger components.

There are common areas of failure for every engine, with some being extremely strong and some only able to handle stock power

Research these limits and install forged components to cope with the power.

It's not unheard of people spending a loads of money on turbo upgrades on the 4G9 only to experience the whole thing throw a rod when it's used in anger.

Larger turbochargers commonly experience low end lag, and smaller turbochargers spool up more quickly but don't have the top end engines power gains.

Thanks to progress the range of turbo chargers is always increasing and we are seeing variable vane turbo chargers, permitting the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbo chargers divert the exhaust flow into 2 channels and feed these at differently angled vanes in the turbo. They also help the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large power gains, although more difficult to configure. We have this article covering twinchargers if you want to read more.

Tips about fuel supply on the 4G9

Don't miss you'll need to boost the fuel delivery when you are increasing the performance - it makes the car more thirsty. Care modifiers usually say to be generous with your injector capacity.

As a rule of thumb add 20% when buying an injector, helps cope with injector deterioration and gives you some spare capacity should the engine require more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended 4G9 performance exhaust upgrades

You may need to increase your exhaust system with an upgraded one is if the existing exhaust is actually causing a flow problem.

On most factory exhausts you'll find the exhaust flow rate is fine even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts generally help improve air flow out of the engine but do not go too wide or you may end up will reduce the flow rate. Stick to one and a half to two and half inches for best results.

Typically exhaust restrictions can be traced to the catalyst and filters installed, so adding a freer flowing high performance alternative will help avoid this restriction.

Catalyst removal (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the 4G9

Like most engines an 4G9, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the 4G9, failure to do this will exacerbate engine wear, on a tuned 4G9 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your 4G9 why not pop over to the forums at TorqueCars where you can chat about 4G9 tuning options and read about others projects who may be planning to do similar modifications on their 4G9.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with upgrades on your 4G9, it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...


Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article