Modding uprating the Mitsubishi 4G3 engine!

Modifying and improving: "4G3 Modifications"

4G3 Modifications Guide

How to modify and upgrade the Mitsubishi 4G3

"Comprehensive guide to tuning the Mitsubishi 4G3 engine!"

Forums like the one at TorqueCars are frequently getting emails requesting info on how to improve the 4G3 from people wanting to know what are the best 4G3 power upgrades. So let us look into Mitsubishi 4G3 modifications and outline the best modifications on this great engine and point out some frequent tuning mistakes along the way.

The Mitsubishi 4G3 really good project engines and with carefully chosen sports mods like ECU maps, turbo upgrades and camshafts you will definitely improve your driving experience.

In this article we outline options for your 4G3 tuning and point out the optimum mods that work.

Just because particular modifications are are common on 4G3 it doesn't mean you should fit it, so we'll focus on the top modifications that will give your 4G3 the best power gain for you spend.

Without us subscribing to the popular mentality of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

4G3 induction kits

Improving air intake on the 4G3

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

So the aim to any car tuning task to feed air and fuel into each cylinder but this has a knock on effect with the air flow sensor.

It is not unusual that there is a limitation in the air flow sensor AFM/MAF on the 4G3 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 sapped bhp and torque at a much lower level.

Engines intake headers carry the air during the suck phase from the air filter and allow it to be drawn into the engine cylinders.

The bore size, shape and rate of flow of the Headers can make a substantial change to fuel delivery on the 4G3.

I usually find air intake manifolds are improved through motorsport parts, although a few car makers provide well optimised air intake manifolds.

Increasing the 4G3 valve size, doing some port matching and head flowing will also increase bhp and torque, and importantly will permit increasing the bhp and torque increase on other parts.

4G3 performance cam tips.

Each engine responds better to less aggressive camshaft durations so set your engine up on a rolling road.

The ecu map and injectors and fuel pump also will say much on the torque gains you'll make.

Altering valve durations can alter the torque 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.

Significant air intake, and exhaust improvements on the 4G3 can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

NB: Fast road camshafts normally raise the power over the rev range, you could sacrifice a little bottom end torque but your high end rpm power will be higher.

Race camshafts, raise the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

For a car used daily you should ideally to optimize your power band to your cars usage.

I'd be gobsmaked if you have ever thought a 4G3 Motorsport cam is a pleasure to live with when driving in heavy traffic.

Stage 1, 2 and 3 mods for the 4G3

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 4G3 parts:

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

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

Stage 2 4G3 parts:

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

Stage 3 4G3 parts:

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

The 4G3 power plant respond well to mods and thankfully there are quite a few choices of parts and tuning parts around.

Mapping will help fully realize the full potential of all the parts you've done to your 4G3.

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 will rely on the parts you've applied and the condition of your engine.

Turbo modifications on the 4G3

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 4G3.

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 an engine has forced induction tuning parts are relatively easy and you will discover turbo engines are built using stronger components.

There are weak spots for every engine, with some being extremely strong and some only just able to handle stock power

Research these limitations and fit higher quality crank and pistons to cope with the power.

It's not unheard of tuners spending a loads of money on turbocharger upgrades on the 4G3 only to suffer the indignity of watching the engine block literally blow up just after it's completed.

Larger turbos often experience a bottom end lag, and small turbos spool up really quickly but don't have the peak end engines power gains.

We are pleased that the world of turbo chargers is always moving on and we are seeing variable vane turbo chargers, allowing 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 a couple of channels and feed these at differently angled vanes in the turbocharger. 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 bhp gains, although harder to install. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the 4G3

Don't forget to raise the fuel delivery when you are increasing the performance - it makes the car more thirsty. At this point we flag up the need to be generous with your injectors flow rate.

The rule of thumb is to add 20% capacity when buying an injector, this allows for injector deterioration and provides a bit of spare capacity should the engine need 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 4G3 performance exhaust upgrades

You should look to uprate your exhaust system with an upgraded one is if the current exhaust is creating a restriction in flow.

On most factory exhausts you should find that the flow rate is ok 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 will certainly help air flow from the engine but do not go too big or you could will reduce the flow rate. Stick to one and a half to two and half inches as a rule of thumb.

Typically exhaust restrictions are in the catalysts installed, so adding a freer flowing race alternative will help avoid this restriction.

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

Faults issues and things to look out for on the 4G3

Like most engines an 4G3, 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 4G3, failure to do this will exacerbate engine wear, on a tuned 4G3 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 4G3 why not pop over to the forums at TorqueCars where you can chat about 4G3 tuning options and read about others projects who may be planning to do similar modifications on their 4G3.

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