Modding tuning and best performance upgrades on the Subaru EJ20 engine!

Modifying and improving: "EJ20 Modifications"

EJ20 Modifications Guide

How to modify and upgrade the Subaru EJ20

"Comprehensive guide to tuning the Subaru EJ20 engine!"

Popular tuning sites like TorqueCars often are seeing threads about how to improve the EJ20 from people wanting to know what are the best tips on EJ20 mods that work. So let us look into Subaru EJ20 upgrades and outline the best modifications on this great engine and point out some problems along the way.

This pages aim is provide a guide to EJ20 tuning and highlight the best modifications for your car. Subaru EJ20 are fantastic to work on and with the best uprated modifications like remapping, turbo improvements and camshafts you will noticeably maximise your driving opportunities.

The best EJ20 parts on an engine are as we have found the ones that give the best power gain for your hard earned cash.

We won't be swayed by popular EJ20 parts, they need to be cost effective.

EJ20 induction kits

Improving air intake on the EJ20

You need air matched to fuel for an engine to work. If there is insufficient fuel then it will run lean, if there is little flow of air it runs rich resulting in lost 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 Getting air into the EJ20 engine is the main goal to any engine tuning job.

It is not unusual that there is a limit in the air flow sensor AFM/MAF on the EJ20 when loads more air is being drawn into the engine.

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

Intake headers flow the air from the air cleaner and allow it to be pulled into the engine cylinders with fuel for the squish phase.

Structure and flow characteristics of the air Intake manifold can make a large change to fuel atomisation and engine efficiency on the EJ20.

It's not uncommon that intake are in dire need of a performance upgrade, although a few OEM provide reasonably good intake.

Increasing the EJ20 valve size, doing some EJ20 port enlargement and head flowing will also improve bhp and torque, the fantastic side effect is it will give you raising the bhp and torque increase on other upgrades.

EJ20 performance cam tips.

Each engine responds better to mild cam durations so set your engine up on a rolling road.

The map and fuelling also have an effect on the power gains you'll get.

Extending exhaust or intake 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 & exhaust durations will alter depending on the chosen camshaft profile, so large torque gains are on offer for camshaft upgrades.

NB: Fast road camshafts tend to bump the power through the rev band, you may lose a little low end bhp but the top end will improve.

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

A Motorsport and race camshaft won't do well if driving around busy urban areas.

You should ideally match your power band to your cars usage so for a typical daily driver stick with a fast road EJ20 camshaft

Stage 1, 2 and 3 mods for the EJ20

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 EJ20 parts:

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

Stage 2 EJ20 parts:

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

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

Stage 3 EJ20 parts:

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

Plan your options and then buy your parts and set yourself a power target to avoid costly mistakes.

ECU mapping will help unlock the full potential of all the parts you've done to your EJ20.

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 may rely on the parts you've fitted and the condition of your engine.

Turbo modifications on the EJ20

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 EJ20.

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

When your car has forced induction parts are simpler to install and we find turbocharged engines are built using uprated components.

However every engines have weakspots

Research these limits and fit stronger pistons, crank and engine components to handle the power.

We've seen mechanics spending a lot of money on turbocharger upgrades on the EJ20 only to suffer the humiliation of seeing the motor catastrophically fail just after it's first rolling road session.

Large upgraded turbo units tend to experience a bottom end lag, and little turbo units spool up more quickly but do not have the top end bhp gains.

In the last 10 years the selection of turbo units is always moving on and we are seeing variable vane turbo units, permitting the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbo units divert the exhaust flow into a couple of channels and direct these at differently angled vanes in the turbocharger. They also increase the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large performance gains, although more difficult to get working. We have this in depth look at twinchargers if you want to read more.

Tips about fuel supply on the EJ20

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

More bhp needs more fuel. Experienced mechanics will tell you to over specify your flow rate on the injectors.

As a rule of thumb add 20% capacity when buying an injector, helps cope with injector deterioration and provides you some spare capacity should the engine require 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 EJ20 performance exhaust upgrades

The only time you should look to replace your exhaust system with an upgraded one is if the current exhaust is actually causing a restriction in flow.

On most factory exhausts you should find that your 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.

Don't go with the largest exhaust you can source this will slow up the exhaust flow rate - the best 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.

The usual suspects causing problems in your exhaust flow rate are traced to the catalysts installed, so adding a freer flowing performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the EJ20

Like most engines an EJ20, 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 EJ20, failure to do this will exacerbate engine wear, on a tuned EJ20 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 EJ20 why not pop over to the forums at TorqueCars where you can chat about EJ20 tuning options and read about others projects who may be planning to do similar modifications on their EJ20.

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