MENUTuning the Subaru EJ22
"Building the best modified Subaru EJ22 engine!"
Carref prides itself on providing the latest tips and guides to your modification project.
The Subaru EJ22 are awesome to work on and with the ultimate performance upgrades like remapping, turbo upgrades and camshafts you will maximise your driving fun.
In this article we examine EJ22 tuning and show the premier modifications for your car.
We rely on our visitors to pass on tips and tell us about their projects and what worked on their car, and this article is the culmination of the feedback we have received. First let us look at the history and specs of this engine and then consider which tuning modifications work best on it.
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)
Tuning the Subaru EJ22 and best EJ22 performance parts.
What are the most effective EJ22 upgrades
Just because particular upgrades are are common on EJ22 it doesn't mean its worth having, instead we'll best upgrades that will give your EJ22 the best power gain for you money.
Significant gains on the EJ22 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the engines power and power output.
Fast road cams commonly increase the bhp over the rev range, you could drop a little bottom end torque but the higher rpm power will be lifted.
Motorsport and race cams, increase the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.
On a road car you need to match your engines power to your driving style.
I'd be amazed if you have ever thought a EJ22 Motorsport camshaft is a pleasure to live with when driving in heavy traffic.
Some EJ22 engines respond better to more or less aggressive camshaft durations so view each engine as unique.
The ECU mapping and injectors and fuel pump also will say much 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.
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How to tune your car
- Improve the handling
Focus on Suspension improvements, such as coilovers and make sure the bushings are in good order and that the alignment is correct. Then focus on improving the brakes, with a big disk brake conversion kit and fast road brake pads.
- Remove restrictions
Focus on the intake and exhaust with filters being the common point of restriction in a tuned car. Intercoolers may also become restrictive on turbo engines so this may also need to be uprated.
- Burn more fuel & air
Increase the fuelling so it matches the air coming into the engine. The ratio is important so you need to improve the fuel pump and injectors, so the head mods, big valve conversions, fast road camshafts and forced induction upgrades extra supply of air is adequately met.
- Test and replace any weak parts
Weak areas are commonly the clutch, the turbocharger and pistons and crankshaft in a highly tuned engine. Makes sure these components will cope with your power aspirations.
- The Tune or Remap
A cars ECU controls the fuel, timing, spark and even the turbo in some cases, so to fully extract your gains you should remap the car last and this will fully release the power. Some cars are easy to map, and others require piggyback ECU's or aftermarket ECU's but this is the most vital step of your tuning project.
Modifying to Stage 1:
Drilled & smoothed airbox, Sports exhaust manifold, Remaps/piggy back ECU, Fast road camshaft, Panel air filters, Intake headers.
Modifying to Stage 2:
Ported and polished head, high flow fuel injectors, induction kit, Fast road cam, fuel pump upgrades, Sports catalyst & performance exhaust.
Modifying to Stage 3:
Internal engine upgrades (head flowing porting/bigger valves), Adding or Upgrading forced induction (turbo/supercharger), Competition cam, Twin charging conversions, Crank and Piston upgrades to alter compression, Engine balancing & blueprinting.
Mapping should help to fully realize the full potential of all the upgrades you've done 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 will rely on the upgrades you've carried out and the condition of your engine.
Pushing air into the EJ22 engine is the main goal to any engine modification job.
Intake take the air from the intake filter and allow it to be drawn into the engine and mixed with fuel.
The bore size, shape and flow rate of the Air Intake manifolds can make a large effect on to fuel atomisation on the EJ22.
Most air intake manifolds are begging for aftermarket tuning parts, although some car makers provide reasonably well designed air intake manifolds.
Increasing the EJ22 valve size, getting EJ22 port enlargement and head flowing will also lift performance, & more importantly will afford you a better performance increase on other upgrades.
Which turbo upgrades are best?
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 significant power gains.
If an engine has forced induction parts are going to net you a larger power gain and you'll see that turbocharged engines are made using better components.
However you will find an engines will have power limits
It is important to find these limitations and fit better pistons and crank to survive the power.
There are many people spending a lot of money on turbo upgrades on the EJ22 only to watch the engine explode just after it's been enthusiastically driven.
Large turbos tend to suffer no power at low rpm, and smaller turbos spool up more quickly but do not have the top end engines power gains.
Over the last 20 years the market of turbochargers is always evolving and we commonly find variable vane turbochargers, allowing the vane profile is altered according to speed to lower lag and increase top end bhp and torque.
Twin scroll turbochargers divert the exhaust gases into 2 channels and feed these at differently designed vanes in the turbo charger. They also boost the scavenging effect of the engine.
It is common that there is a limitation in the air flow sensor AFM/MAF on the EJ22 when loads more air is being sucked into the engine.
You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited bhp and torque at a much lower level.
Adding a supercharger or additional turbo will make large torque gains, although more difficult to configure. We have this article covering twinchargers if you want to read more.
Fuelling
When you increase the torque you will need to uprate to the fuel delivery.
More torque needs more fuel. 
We would recommend you to over specify your injector capacity.
As a rule of thumb add 20% capacity when specifying an injector, this takes into account injector deterioration and gives a bit of 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.
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
4 Cylinder NASP engines
- 58 PSI 285cc/min 200hp
- 58 PSI 426cc/min 300hp
- 58 PSI 568cc/min 400hp
- 58 PSI 853cc/min 600hp
Choosing the right performance exhaust
One of the most common mistakes and problems we see in tuning projects is usually down to the exhaust, or rather a poorly chosen exhaust for your engine.
You may need to upgrade your exhaust if your current exhaust is creating a flow problem.
On most factory exhausts you should find that your flow rate is still good 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 balance the flow of gases through the engine.
But if your exhaust pipe is too large, ie: it's over 2.5 inches bore, you will lose much of the exhaust flow rate and end up lacking power and torque.
Common exhaust restrictions come around the filters installed, so adding a better flowing race alternative will help avoid this restriction.
Weak spots Issues & problem areas on the EJ22
The EJ22 engines are generally reliable and solid as long as they are regularly serviced and maintained.
Regular oil changes are vital on the EJ22, especially when tuned and will help extend the life and reliability of the engine.
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.
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 EJ22 articles which are continually updated.
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