Tuning the Mitsubishi 4G9

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

We are always getting posts requesting info on the premier 4G9 power upgrades. So let us look into Mitsubishi 4G9 parts and outline the best upgrades on this great engine and point out some potential pitfalls along the way.

The Mitsubishi 4G9 great bases for a tuning project and with carefully picked tuning upgrades like ECU maps, turbo kits and camshafts you will definitely enhance your driving fun.

We shall examine 4G9 tuning and show the premier upgrades.

When talking about the top parts for your 4G9 engine, we are going to focus on the upgrades that give the best power gain for you money.

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 cams usually boost the bhp and torque throughout the rpm range, you may sacrifice a little bottom end torque but your high end rpm power will be better.

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

A Motorsport cam won't do well if on the daily commute.

You should ideally match your engines power to your usage of the car so for a daily driver stick with a fast road 4G9 cam

Some 4G9 engines respond better to extreme camshaft durations so view each engine as unique.

The ecu map and injectors and fuel pump also will make differences on the power gains you'll hit.

Longer 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.

4G9 Tuning Stages

Stage 1 4G9 modifications: Sports exhaust manifold, Fast road camshaft, Panel air filters, Drilled & smoothed airbox, Remaps/piggy back ECU, Intake headers.

Stage 2 4G9 modifications: Ported and polished head, high flow fuel injectors, fuel pump upgrades, Fast road cam, induction kit, Sports catalyst & performance exhaust.

Stage 3 4G9 modifications: Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression, Adding or Upgrading forced induction (turbo/supercharger), Engine balancing & blueprinting, Competition cam, Twin charging conversions.

Carefully think through your options and then acquire your tuning parts and set yourself a power target to avoid disappointment.

A remap should help to to establish the full potential of all the upgrades you've done to your 4G9.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome usually depend much on the upgrades you've carried out and the condition of your engine.

It is the aim to any engine tuning task to force fuel and air into your 4G9

Air Intake manifolds transmit the air from the air cleaner and allow it to be fed into the engine cylinders.

Structure and rate of flow of the Intake manifold can make a large effect on to fuel mixing and power on the 4G9.

It's not uncommon that headers are ripe for aftermarket tuning parts, although a few manufacturers provide decently flowing headers.

Adding a 4G9 larger valve kit, doing some port work and head flowing will also boost power, & importantly will give you a greater power increase on other tuning parts.

Turbo upgrades for the 4G9

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 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 excellent power gains.

When your motor is turbocharged, upgrades are going to net you a larger power gain and you will discover turbo charged engines use stronger components.

However most engines will have power limits

Research these limitations and fit better quality components to survive the power.

We see many tuners spending a loads on turbocharger upgrades on the 4G9 only to have the car literally blow up just after it's finished.

Larger capacity turbos commonly suffer no power at low rpm, and little turbos spool up much more quickly but don't have the peak end bhp gains.

We are pleased that the choice of turbo units is always improving and we now see variable vane turbo units, permitting the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbo units divert the exhaust gases into two channels and direct these at differently angled vanes in the turbocharger. They also improve the scavenging effect of the engine.

You'll commonly see there is a restriction in the air flow sensor AFM/MAF on the 4G9 when considerably more air is being drawn into the engine.

You'll see that 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.

Adding a supercharger or additional turbo will make large torque gains, although more challenging to configure. We have this article covering twinchargers if you want to read more.

Uprating 4G9 fuel injectors

Don't overlook the need to boost the fuelling when you are increasing the bhp - it makes the car more thirsty. It is important to over specify your injector capacity.

The accepted safe increase is to add 20% when buying an injector, this takes into account injector deterioration and allows some spare capacity should the engine need 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.

Best 4G9 performance exhausts

You may need to replace your exhaust if your exhaust is actually creating a restriction in flow.

On most factory exhausts you'll see the exhaust 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 through the engine but do not go too big or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

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

Problems and issues to look out for on the 4G9

The 4G9 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the 4G9, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your 4G9 engine please join us in our friendly forum where you can discuss tuning options in more detail with our 4G9 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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

We really like hearing from our readers, and hearing about which upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our 4G9 guides and tips are kept up to date.

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