Modding tuning and best performance upgrades on the Mitsubishi 4B1 engine!

Tuning guide "4B1 Modifications"

4B1 Modifications Guide

How to modify and upgrade the Mitsubishi 4B1

"Comprehensive guide to performance parts and tuning the Mitsubishi 4B1 engine!"

TorqueCars are regularly getting messages requesting info on how to improve the 4B1 from people inquiring about getting more power from the 4B1 and wanting to know what are the greatest 4B1 mods that work. So let us look into Mitsubishi 4B1 upgrades and outline the best upgrades on this great engine and point out some problems along the way.

The Mitsubishi 4B1 are good project engines and with a few sensible performance mods like remaps, turbo improvements and camshafts you will really maximize your driving pleasure.

Let us review and look at 4B1 tuning and report on the greatest modifications.

When talking about the best parts for your 4B1 engine, we are going to focus on the upgrades that give the best power gain for you spend.

4B1 induction kits

Improving air intake on the 4B1

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 little flow of air it runs rich losing power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Forcing more fuel and air into each cylinder is the main goal to any tuning job.

It is not unusual that there's a limitation in the air flow sensor AFM/MAP on the 4B1 when a lot more air is being drawn 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 performance at a much lower level.

Intake flow the air from the filter and allow it to be sucked into the engine and mixed with fuel.

Design and flow rate of the Intake headers can make a large effect on to fuel engine efficiency on the 4B1.

Most intake manifold are begging for an upgrade, although a few car makers provide decently flowing intake manifold.

Fitting big valve kits, doing a bit of port work and head flowing will also improve performance, and importantly will raise potential for increasing the performance increase on other parts.

4B1 performance cam tips.

Different 4B1 engines respond better to extreme camshaft durations so set your engine up on a rolling road.

The engine timing and injectors and fuel pump also have a large bearing on the power gains you'll get.

A longer valve duration 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.

Significant air intake, and exhaust improvements on the 4B1 can be made from cam upgrades. Changing the cam profile alters the intake and exhaust durations on the engine and can dramatically change the bhp and power output.

NB: Fast road cams commonly push up the torque across the rpm band, you could sacrifice a little low down bhp but your top end will be higher.

Competition cams, 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 car driven daily you need to match your power band to your typical driving style.

I would be surprised if you have found a 4B1 Motorsport cam is a pleasure to live with when driving around busy urban areas.

Stage 1, 2 and 3 mods for the 4B1

Stage 1 4B1 parts:

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

Stage 2 4B1 parts:

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

Stage 3 4B1 parts:

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

The 4B1 units make great tuning projects and we note that there are plenty of modifications and performance parts around.

ECU mapping allows a tuner to release the full potential of all the modifications you've done to your 4B1.

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

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 will differs on the modifications you've applied and the condition of your engine.

Turbo modifications on the 4B1

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 4B1.

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 is turbo charged upgrades are relatively easy and we find turbocharged engines are made using uprated components.

There are common areas of failure for every engine, with some being extremely strong and some only just able to handle stock power

We recommend you find these limits and fit forged components to handle the power.

It's not unheard of people spending a lots of money on turbo charger upgrades on the 4B1 only to suffer the indignity of watching the engine block literally blow up just after it's used in anger.

Large capacity turbos tend to experience a bottom end lag, and low capacity turbos spool up quickly but do not have the high rpm engines power gains.

Thanks to progress the range of turbo chargers is always developing and we are seeing variable vane turbo chargers, allowing the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbo chargers divert the exhaust gases into a couple of channels and push these at differently angled vanes in the turbo charger. They also boost the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large torque gains, although more complex to get working. We have this guide to twinchargers if you want to read more.

Tips about fuel supply on the 4B1

Don't overlook the need to boost the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. Don't forget to over specify your flow rate on the injectors.

The accepted safe increase is to add 20% when fitting an injector, which takes into account injector deterioration and allows 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 4B1 performance exhaust upgrades

You only need to to upgrade your exhaust system with an upgraded one is if the existing exhaust is actually creating a restriction.

On most factory exhausts you'll see the flow rate is still 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 generally help improve air flow out of the engine but do not go too big 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 are in the catalysts installed, so adding a higher flowing race alternative will help avoid this restriction.

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

Faults issues and things to look out for on the 4B1

Like most engines an 4B1, 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 4B1, failure to do this will exacerbate engine wear, on a tuned 4B1 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 4B1 why not pop over to the forums at TorqueCars where you can chat about 4B1 tuning options and read about others projects who may be planning to do similar modifications on their 4B1.

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