Modding and performance tuning parts for the Subaru EZ engine!

Modifying and improving: "EZ Modifications"

EZ Modifications Guide

How to modify and upgrade the Subaru EZ

"Comprehensive guide to tuning the Subaru EZ engine!"

TorqueCars are frequently getting emails asking how to improve the EZ from people wanting to know what are the best EZ modifications. So let us look into Subaru EZ mods and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

We shall detail the best approach to EZ tuning and highlight the premier upgrades. Subaru EZ offer good returns when tuned and with the best tuning mods like remapping, turbo upgrades and camshafts you will greatly increase your driving pleasure.

The top EZ upgrades on an engine are sensibly the ones that give the biggest return for your money.

We won't be swayed by popular EZ upgrades, they need to be cost effective.

EZ induction kits

Improving air intake on the EZ

You need fuel and air for an engine to work. If there is not enough fuel then it will run lean, if there is insufficient air it runs rich losing power which risks damage to the EZ. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Shoving more air and fuel into your EZ is vital to any engine performance tuning task.

It is not unusual that there's a limit in the air flow sensor MAF/MAP on the EZ 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 bhp and torque at a much lower level.

Engines intake headers transmit the air during the suck phase from the filter and allow it to be fed into the engine and mixed with fuel.

The size of bore and shape and rate of flow of the Intake headers can make a big difference to to fuel delivery on the EZ.

Many mass produced engine intake are in desperate need of motorsport parts, although a few car makers provide fairly well optimized intake.

Increasing the EZ valve size, doing some port matching and head flowing will also lift torque, & importantly will make space for increasing the torque increase on other parts.

EZ performance cam tips.

Each engine responds better to more or less aggressive camshaft durations so view each engine as unique.

The ecu map and fuel pump and injectors also have an effect on the power gains you'll make.

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.

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 engines power gains are on offer for camshaft upgrades.

NB: Fast road camshafts tend to boost the bhp and torque through the rpm band, you might lose a little low down torque but higher rpm power will be better.

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

In a car used daily you need to optimize your torque band to your cars usage.

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

Stage 1, 2 and 3 mods for the EZ

Stage 1 EZ parts:

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

Stage 2 EZ parts:

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

Stage 3 EZ parts:

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

Carefully think through your options and then source your modifications and set yourself a power target to avoid wasting your time and money.

Remapping should help to to establish the full potential of all the mods you've done to your EZ.

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

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

Turbo modifications on the EZ

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 EZ.

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

If a car is fitted with a turbo mods are relatively easy and you will discover turbocharged engines are built using more solid components.

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

Research these restrictions and install higher quality components to cope with the power.

It's not unheard of drivers spending a lots of money on turbocharger upgrades on the EZ only to experience the motor throw a rod just after it's first rolling road session.

Larger turbos often suffer low end lag, and low capacity turbos spool up really quickly but do not have the peak end power band gains.

Thanks to new tech the range of turbo chargers is always moving on and we now see variable vane turbo chargers, permitting the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust flow into a couple of channels and push these at differently designed 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 bhp and torque 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 EZ

When you increase the power you will need to increase to the fuel delivery.

More power needs more fuel. Most tuners we speak with say to be generous with your flow rate on the injectors.

The accepted safe increase is to add 15% capacity when fitting an injector, which takes into account injector deterioration and affords 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 EZ performance exhaust upgrades

We'd only recommend you look to uprate your exhaust system with an upgraded one is if the existing exhaust is actually creating a restriction in flow.

On most factory exhausts you should find that the flow rate is still 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.

Don't go with the widest exhaust you can find this will slow the exhaust rate - the best exhausts for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

Usual exhaust restrictions come around the filters installed, so adding a better flowing race alternative will help avoid this restriction.

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

Faults issues and things to look out for on the EZ

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

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