Mitsubishi 4B4 Tuning

"All you need to know about tuning the Mitsubishi 4B4 engine!"

The Mitsubishi 4B4 make awesome project engines and with the best uprated tuning mods like a remap, turbo improvements and camshafts you will noticeably maximize your driving fun.

Our aim here is to detail the best approach to 4B4 tuning and summarise the optimum mods that work.

History, Power & Specs of the 4B4 Engine

Inline turbo/intercooled 4-cylinder DOHC 16v MIVEC

4B40

120 kW (161 hp) at 5500 rpm 250 Nm (184 lbft) at 1800 to 4500 rpm

Tuning the Mitsubishi 4B4 and best 4B4 performance parts.

Best 4B4 parts

When talking about the optimum modifications for your 4B4 engine, we are going to focus on the ones that give the best power gain for you spend.

Altering your 4B4 camshaft will make a dramatic difference to the engine engines power. Choosing a higher performance camshaft profile raises the engines power accordingly.

Fast road camshafts tend to push up the performance through the rev range, you could sacrifice a little bottom end power but your top end will be higher.

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

For a typical daily driver you need to optimize your torque band to your preferences.

I'd be surprised if you have found a 4B4 Motorsport camshaft is a pleasure to live with when driving around busy urban areas. This is because a competition cam causes a very lumpy idle, and makes the car more prone to stall or jerk along in stop start traffic, sadly though many ignore this and end up ruining a perfectly good car and having to revert back to a fast road, or OEM cam profile.

Different 4B4 engines respond better to more aggressive camshaft durations than others.

The map and injectors and fuel pump also have an effect 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.

Typical stage 1 mods often include: drilled & smoothed airbox, Intake headers, Panel air filters, Sports exhaust manifold, Remaps/piggy back ECU, Fast road camshaft.

Typical stage 2 mods often include: fuel pump upgrades, Fast road cam, Ported and polished head, Sports catalyst & performance exhaust, high flow fuel injectors, induction kit.

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

The 4B4 power plant are great to work on and we see that there is a growing number of modifications and performance parts out there.

ECU flashing allows a tuner to unlock the full potential of all the tuning mods you've done to your 4B4.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your mileage may depend much on the tuning mods you've fitted and the condition of your engine.

Pulling air into the 4B4 engine is the main goal to any engine modification job.

Air Intake manifolds take the air from the filter and allow it to be drawn into the engine cylinders.

Design and rate of flow of the Plenum can make a substantial effect on to fuel engine efficiency on the 4B4.

It's not uncommon that intake are in dire need of aftermarket parts, although a few manufacturers provide decently flowing intake.

Fitting big valve kits, doing some 4B4 port enlargement and head flowing will also raise torque, and significantly will afford you increasing the torque increase on other parts.

4B4 Turbo upgrades

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 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.

When a car has a turbo already fitted upgrades are simpler to install and you'll see that turbocharged engines are made with uprated components.

There are reliable limits for every engine, with some being very over engineered and some only just able to handle stock powerResearch these limitations and upgrade to higher quality crank and pistons to handle the power.

It's not unheard of people spending a loads on turbo charger upgrades on the 4B4 only to watch the engine literally blow up just after it's been enthusiastically driven.

Larger turbo chargers will usually suffer no power at low rpm, and smaller turbo chargers spool up really quickly but don't have the high rpm engines power gains.

Thanks to new tech the market of turbochargers is always increasing and we commonly find variable vane turbochargers, permitting the vane angle is altered according to speed to lower lag and increase top end power.

Twin scroll turbochargers divert the exhaust flow into 2 channels and push these at differently profiled vanes in the turbo. They also increase the scavenging effect of the engine.

It is common that there is a limitation in the air flow sensor MAF/MAP on the 4B4 when a lot more air is being sucked into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited performance at a much lower level.

Adding a supercharger or additional turbo will make large bhp gains, although harder to setup. We have this guide to twinchargers if you want to read more.

Fuelling

You will need to ensure that the engine is not starved of fuel so will need to ramp up the fuelling when you start exceeding 20% of a bhp increase.Don't forget to over specify your injector capacity.

The rule of thumb is to add 20% capacity when specifying an injector, which takes into account injector deterioration and provides you 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.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder turbocharged engines

  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp
  • 58 PSI 682cc/min 400hp
  • 58 PSI 1022cc/min 600hp

4B4 Performance Exhausts

You only need to to improve your exhaust if your current exhaust is creating a restriction in flow.

On most factory exhausts you'll see the flow rate is 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 equal out the flow of gases through the engine.

But if your exhaust is too big, ie: it's over 2.5 inches bore, you will lose much of the exhaust flow rate and end up lacking power and torque.

Typically exhaust restrictions come around the emissions filters installed, so adding a higher flowing high performance aftermarket one will improve air flow, and rather than doing an illegal decat, will keep the car road legal.

Weak spots, Issues & problem areas on the 4B4

The 4B4 engines are generally reliable and solid as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the 4B4, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your 4B4 engine please join us in our friendly forum where you can discuss 4B4 tuning options in more detail with our 4B4 owners. It would also be worth reading our unbiased Mitsubishi tuning articles to get insights into each modification and how effective they will be for your car.

Please help us improve these tips by sending us your feedback in the comments box below.

We love to hear what our visitors have got up to and which parts work best for them on each model of car. Comments are used to improve the accuracy of these 4B4 articles which are continually updated.

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