Tuning the Subaru EJ22

"Comprehensive guide to tuning the Subaru EJ22 engine!"

Let us provide a guide to EJ22 tuning and outline the best mods that work. Subaru EJ22 are popular engines and with carefully picked parts like a remap, turbo upgrades and camshafts you will definitely enhance your driving enjoyment.

When talking about the best ultimate for your EJ22 engine, we are going to concentrate on the parts that give the best power gain for you money.

Altering your EJ22 camshaft will make a dramatic difference to the engine bhp. Choosing a higher performance camshaft profile raises the bhp accordingly.

NB: Fast road camshafts usually bump the bhp across the rev band, you could drop a little low down power but the high end rpm power will be higher.

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

A Motorsport cam will just annoy you whilst driving in heavy traffic.

You should ideally match your engines power to your usage of the car so for a daily driver stick with a fast road EJ22 cam

Different EJ22 engines respond better to more aggressive camshaft durations so set your engine up on a rolling road.

The map and fuel pump and injectors also will say much on the bhp gains you'll get.

A longer valve duration 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.

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Guide to the Best Tuning Mods & Upgrades

  1. Mods that Remove a Restriction

    If the intake or exhaust are restricted in any way this will have an impact on your cars performance, so use an induction kit/filter upgrade and better flowing exhaust whenever your tuning creates a flow restriction.

  2. Mods that Improve Handling

    Braking, Suspension and general alignment of the suspension components is vital for any tuning project even before you start increasing power.

  3. Fit Stronger Parts

    Tuned cars will show up weaknesses, typically in the turbochargers, clutch and internal engine components. Whilst most engines can cope with mild tuning mods, TorqueCars recommend that you upgrade the internal components before these weak spots manifest themselves.

  4. ECU Tunes & Remapping

    While some cars can be easily remapped, others may require piggyback ECU's or aftermarket ECU's but this is the most vital step of your tuning project as it fully releases the power from all of your mods and upgrades. Expect 10-20% on NASP engines and 30-40% on turbocharged units.

  5. More Power Needs More Fuel & Air

    Every tuning project will aim to increase the air supply, but fuel supply is just as vital and will need to match the air the engine can utilise. Fuel to Air ratio is vital so upgrade the fuel pump & injectors. Also you can look to perform head mods (flowing and porting), bigger valves, fast road cams and forced induction upgrades to improve fuel.

Stages of Tune

Stage 1 mods: Remaps/piggy back ECU, Panel air filters, Fast road camshaft, Intake headers, Drilled & smoothed airbox, Sports exhaust manifold.

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

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

The EJ22 engine blocks respond well to mods and thanks to their popularity there is a growing number of upgrades and performance parts around.

Remaps allows a tuner to release the full potential of all the parts you've fitted to your EJ22.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your results may vary depending on the parts you've applied and the condition of your engine.

It is the whole point to any car tuning job to shove more air and fuel into each cylinder

Intake manifold carry the air during the suck phase from the air filter and allow it to be sucked into the engine cylinders.

Shape and flow characteristics of the Headers can make a big difference to to fuel atomisation and engine efficiency on the EJ22.

Commonly we find the intake headers are needing aftermarket parts, although some car makers provide fairly well optimized intake headers.

Fitting big valve kits, doing a bit of port work and head flowing will also increase torque, & importantly will permit a better torque increase on other modifications.

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 EJ22

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 your motor is turbocharged, modifications are more reliable and you will discover turbo charged engines are built using uprated components.

However most engines have weakspots

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

We've seen people spending a lots of money on turbo upgrades on the EJ22 only to watch the car literally blow up when it's first rolling road session.

Larger turbos tend to suffer low end lag, and little turbos spool up more quickly but do not have the peak end bhp gains.

Thankfully the market of turbo units is always improving and we now see variable vane turbo units, allowing the vane profile is altered according to speed to lower lag and increase top end bhp.

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

It is not unusual that there's a limitation in the air flow sensor MAP/MAF/AFM on the EJ22 when considerably more air is being pulled into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped performance at a much lower level.

Adding a supercharger or additional turbo will make large power gains, although more challenging to configure. We have this feature on twinchargers if you want to read more.

Fuelling upgrades and mods

You will need to ensure that the engine is not starved of fuel so must look at the fuelling when you start extending past 20% of a bhp and torque increase.It makes sense to be generous with your flow rate on the injectors.

As a rule of thumb add 20% capacity when specifying an injector, helps cope with injector deterioration and provides you some spare capacity should the engine require 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.

Exhaust upgrades and mods

You should look to replace your exhaust if your exhaust is actually creating a flow problem.

On most factory exhausts you should find that the flow rate is ok 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 can help increase the flow of air through the engine.

But if the exhaust pipe is too large, ie: over 2.5 inches bore, you will lose a lot of the exhaust flow rate and end up losing power and torque.

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

Weak spots, Issues & common problem areas on the EJ22

The EJ22 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the EJ22, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

History of the Engine

EJ22E Naturally Aspirated

(1989-1994)

  •  130 bhp (97 kW 132 PS) at 5800 rpm  (137 lbft) at 4800 rpm

(1995-1996)

  •  135 bhp (101 kW 137 PS) at 5800 rpm 140 lbft) at 4800 rpm

(1997-1998)

  • 137 bhp (102 kW 139 PS) at 5400 rpm  (145 lbft) at 4000 rpm

('89-97 Australia)

  • 100 kW (134 hp 136 PS) at 6000 rpm  (139 lbft) at 4800 rpm

EJ222 Naturally Aspirated (1999-2001)

  • 142 bhp (106 kW 144 PS) at 5600 rpm (149 lbft) at 3600 rpm

EJ22T

  •  183 bhp (136 kW 186 PS) fully closed deck
    Legacy 1991-1994

EJ22G

  • 280 PS (206 kW 276 bhp) at 6000 rpm 268 lbft at 3200 rpm
    Impreza STi 22B GC8 series (JDM)

For more information on Tuning your EJ22 engine please join us in our friendly forum where you can discuss tuning options in more detail with our tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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