Modding upgrading and tuning the Mitsubishi 4A9 engine!

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How to modify and upgrade the Mitsubishi 4A9

"Comprehensive guide to performance parts and tuning the Mitsubishi 4A9 engine!"

Sites like TorqueCars are always getting emails asking how to improve the 4A9 from people wanting to know what are the things tuners recommend when it comes to 4A9 modifications. So let us look into Mitsubishi 4A9 tuning mods and outline the best upgrades on this great engine and point out some problems along the way.

The Mitsubishi 4A9 really good project engines and with the optimum tuning mods like remaps, turbo kits and camshafts you will dramatically improve your driving opportunities.

In this article we provide a guide to 4A9 tuning and highlight the premier mods that work.

When talking about the greatest parts for your 4A9 engine, we are going to focus on the upgrades that give the biggest return for your cash.

4A9 induction kits

Improving air intake on the 4A9

You need air matched to fuel for an engine to work. If there is too little fuel then it will run lean, if there is too little air it runs rich losing power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the primary aim to any engine upgrade task to pull more air into the 4A9 engine but this has a knock on effect with the air flow sensor.

You'll commonly see there's a limit in the air flow sensor AFM/MAF on the 4A9 when a lot more air is being sucked into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited torque at a much lower level.

Intake headers transmit the air from the air filter and allow it to be drawn into the engine cylinders.

Structure and flow characteristics of the Headers can make a noticeable difference to to fuel mixing and power on the 4A9.

It's not uncommon that air intake manifolds are improved through performance upgrades, although a few OEM provide decently flowing air intake manifolds.

Fitting big valve kits, carrying out 4A9 port enlargement and head flowing will also boost performance, & importantly will give you raising the performance increase on other upgrades.

4A9 performance cam tips.

Some 4A9 engines respond better to different camshaft durations so view each engine as unique.

The map and fuelling also will make differences on the bhp gains you'll get.

A longer valve duration 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.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen camshaft profile, so large bhp gains are on offer for camshaft upgrades.

NB: Fast road cams commonly boost the bhp throughout the rev band, you may lose a little low end power but the top end will be lifted.

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

A Competition cam makes it harder when in heavy traffic.

You should ideally optimize your bhp range to your driving style so for a car used daily stick with a shorter duration 4A9 cam

Stage 1, 2 and 3 mods for the 4A9

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 4A9 parts:

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

Stage 2 4A9 parts:

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

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

Stage 3 4A9 parts:

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

Plan your options and then buy your parts and set yourself a power target to save yourself from expensive mistakes.

Remapping will help unlock the full potential of all the upgrades you've done to your 4A9.

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 figures achieved may depend much on the upgrades you've done and the condition of your engine.

Turbo modifications on the 4A9

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 4A9.

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

When a car is fitted with a turbocharger mods are going to net you a larger power gain and you'll see that turbo charged engines are built using better components.

However engines will have power limits

See where you'll find these limits and upgrade to forged components to utilize the power.

There are many tuners spending a a stack of money on turbo charger upgrades on the 4A9 only to watch the motor catastrophically fail just after it's been finished.

Larger upgraded turbos often experience low end lag, and low capacity turbos spool up more quickly but don't have the top end engines power gains.

In the last 10 years the market of turbo chargers is always improving and we commonly find variable vane turbo chargers, where 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 two channels and direct these at differently angled vanes in the turbo charger. They also increase the scavenging effect of the engine.

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

Tips about fuel supply on the 4A9

You will need to ensure that the engine is not starved of fuel so will have to uprate the fuelling when you start going beyond 20% of a bhp and torque hike. We would recommend you to over specify your flow rate on the injectors.

The accepted safe increase is to add 20% to the flow rate when fitting an injector, which takes into account 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 4A9 performance exhaust upgrades

Only look to increase your exhaust system with an upgraded one is if the existing exhaust is actually creating a restriction.

On most factory exhausts you'll find your flow rate is good 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 can usually air flow from the engine but avoid an exhaust that is 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 catalysts installed, so adding a better flowing race alternative will help avoid this restriction.

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

Faults issues and things to look out for on the 4A9

Like most engines an 4A9, 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 4A9, failure to do this will exacerbate engine wear, on a tuned 4A9 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 4A9 why not pop over to the forums at TorqueCars where you can chat about 4A9 tuning options and read about others projects who may be planning to do similar modifications on their 4A9.

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