Modding and performance tuning parts for the Mitsubishi 4B4 engine!

Tuners tips on "4B4 Modifications"

4B4 Modifications Guide

How to modify and upgrade the Mitsubishi 4B4

"Comprehensive guide to performance parts and tuning the Mitsubishi 4B4 engine!"

Forums like the one at TorqueCars often are getting posts about how to improve the 4B4 from people wanting to know what are the best 4B4 modifications. So let us look into Mitsubishi 4B4 parts and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

Therefore we examine the options for your 4B4 tuning and report on the best upgrades. Mitsubishi 4B4 are popular engines and with the best motorsport enhancements like a remap, turbo improvements and camshafts you will greatly maximise your driving fun.

The greatest 4B4 tuning mods on an engine are usually the ones that give the best power gain for your hard earned cash.

We won't be swayed by popular 4B4 tuning mods, they need to be cost effective.

4B4 induction kits

Improving air intake on the 4B4

You need air and 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 sapping power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the fundamental goal to any performance tuning task to shove more fuel and air into each cylinder but this has a knock on effect with the air flow sensor.

You'll commonly see there is a limitation in the air flow sensor (AFM/MAF/MAP) on the 4B4 when loads more air is being fed into the engine.

When tuning you may well find you need to get an air sensor or flow meter capable of upto 4 bars to cope with quite large power gains, whereas the OEM air sensor sapped torque at a much lower level.

Intake carry the during the engines suck phase from the filter and allow it to be sucked into the engine cylinders with fuel for the squish phase.

Shape and rate of flow of the Intake can make a large improvement to fuel delivery on the 4B4.

It's not uncommon that intake are crying out for performance upgrades, although a few car makers provide fairly well optimized intake.

Big valve conversions on the 4B4, carrying out port work and head flowing will also boost power, and significantly will give you a better power increase on other parts.

4B4 performance cam tips.

Different 4B4 engines respond better to more or less aggressive cam durations than others.

The map and injectors and fuel pump also have a large bearing on the bhp gains you'll make.

Extending exhaust or intake 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.

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 torque gains are on offer for camshaft upgrades.

NB: Fast road camshafts tend to raise the bhp and torque across the rpm range, you may lose a little low down bhp but the high end rpm power will be better.

Motorsport and 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.

On a car driven daily you must carefully try to match your bhp range to your typical driving style.

I'd never have found a 4B4 Motorsport cam is a pleasure to live with when driving in heavy traffic.

Stage 1, 2 and 3 mods for the 4B4

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 4B4 parts:

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

Stage 2 4B4 parts:

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

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

Stage 3 4B4 parts:

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

The 4B4 engine blocks make great tuning projects and we note that there are increasing numbers of upgrades and performance parts around.

Remapping allows a tuner to to establish the full potential of all the modifications you've done to your 4B4.

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 end result often vary depending on the modifications you've carried out and the condition of your engine.

Turbo modifications on the 4B4

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 4B4.

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.

If a car has forced induction mods are more reliable and you will discover turbo charged engines are built with strengthened components.

There are weak spots for every engine, with some being over specified and some only able to handle stock power

We recommend you find these limits and install better quality crank and pistons to utilize the power.

We've seen drivers spending a a stack of money on turbo upgrades on the 4B4 only to have the car throw a rod when it's finished.

Big turbochargers often suffer no power at low rpm, and small turbochargers spool up really quickly but won't have the peak end torque gains.

Thanks to progress the range of turbochargers is always developing and we commonly find variable vane turbochargers, where the vane profile is altered according to speed to lower lag and increase top end torque.

Twin scroll turbochargers divert the exhaust gases into two channels and direct these at differently angled vanes in the turbo. They also improve 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 challenging to setup. We have this in depth look at twinchargers if you want to read more.

Tips about fuel supply on the 4B4

When you lift the torque you will need to uprate to the fuel system.

More torque needs more fuel. Most tuners we speak with say to be generous with your injector capacity.

As a rule of thumb add 20% to the flow rate when specifying an injector, this 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 4B4 performance exhaust upgrades

The only time you should look to increase your exhaust system with an upgraded one is if your exhaust is creating a flow problem.

On most factory exhausts you should find that the exhaust 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 can help balance the flow of gases through the engine.

But if the exhaust is too large, ie: it's over two and a half inches diameter, you will lose a great deal of the flow rate and end up sapping power and torque.

Typically exhaust restrictions come around the catalyst and filters installed, so adding a higher flowing sports 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 4B4

Like most engines an 4B4, 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 4B4, failure to do this will exacerbate engine wear, on a tuned 4B4 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 4B4 why not pop over to the forums at TorqueCars where you can chat about 4B4 tuning options and read about others projects who may be planning to do similar modifications on their 4B4.

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 tuning parts on your 4B4, 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