Subaru EZ30 Tuning

"All you need to know about tuning the Subaru EZ30 engine!"

So is it possible to get more power from an EZ30 engine? Of course, and this is something we get asked quite often.

So let's look at this fantastic flat 6 engine from Subaru, review it's production history and look at the best modifications for it.

The Subaru EZ30 provide a fun base for your project and with the right uprated parts like remaps, turbo improvements and camshafts you will dramatically increase your driving experience.

Here we detail the best approach to EZ30 tuning and summarise the best mods that work.

History, Power & Specs of the EZ30 Engine

This flat 6 engine featured an exhaust which had a larger bore at higher RPM's thanks to a clever valve. It also used a timing belt and although this is a 6 cylinder engine is is a similar size to the 4 cylinder version offered.

1st Gen EZ30

162 kW 217 hp; 220 PS @ 6,000 RPM 289 Nm 213 lbft@ 4,400 RPM

158 kW; 215 PS (212 hp) @ 6,000 RPM 280 Nm (210 lbft) @ 4,400US

  • 2000–2004 Subaru Outback H6
  • 2002-2003 Subaru Legacy GT30
  • 2000–2003 Subaru Legacy Lancaster 6
  • 2002-2003 Subaru Legacy RS30

Turbocharged EZ30

294 kW 394 hp; 400 PS @ 6,400 RPM 550 Nm 410 lbft @ 3,600 RPM

2nd Gen EZ30

180 kW 240 hp; 240 PS @ 6,600 RPM 297 Nm 219 lbft @4,200 RPM

  • 2003–2009 Subaru Legacy 3.0R
  • 2005–2009 Subaru Outback 3.0R
  • 2006–2007 Tribeca

Tuning the Subaru EZ30 and best EZ30 performance parts.

Best EZ30 upgrades

Just because particular mods are popular with EZ30 owners it doesn't mean it is good, instead we will recommend only what we regard are the best mods that will give your EZ30 the biggest power gain return for your cash.

Altering your EZ30 camshaft will make a dramatic difference to the engine engines power. Choosing a higher performance camshaft profile raises the engines power accordingly.

Fast road cams commonly raise the bhp and torque across the rpm range, you could drop a little low end torque but your top end will be lifted.

Motorsport cams, raise the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

In a typical daily driver should ideally to optimize your torque band to your preferences.

I'd be completely gobsmacked if you have found a EZ30 Competition camshaft is a pleasure to live with when on the daily commute, because the lumpy idle will make the car prone to stall and smooth driving at low rpm becomes impossible. If you are developing a track car this doesn't matter as you are in the high end of your RPM range anyway and that is where you want the power to be.

Some EZ30 engines respond better to extreme cam durations so set your engine up on a rolling road.

The ecu map and fuelling also will say much on the bhp gains you'll achieve.

Altering valve durations 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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Best Engine Mods for your car

  1. Mapping - remapping provides the most advantage in terms of cost savings,  aftermarket ECUs, and piggyback ECUs are all alternatives.
  2. Fast road cams are one of the most significant mechanical changes, but they must be installed by someone who knows what they're doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft.
  3. Intake and Exhaust - Note that on their own these mods will NOT ADD POWER in most cases, but they can help enhance power after other mods by removing the restriction.
  4. Upgrades to turbochargers and superchargers - forced induction is the most efficient approach to increase air supply, allowing you to burn more fuel and make more power. It is one of the most costly upgrades but provides the best gains.
  5. Head work - The goals of porting and flowing the head are to get air flowing into the engine while removing flow restrictions and turbulence.
  6. Typical stage 1 mods often include:
    drilled & smoothed airbox, Fast road camshaft, Sports exhaust header/manifold, Panel air filters, Remaps/piggy back ECU, Intake manifolds.

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

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

    Review your options and then source your upgrades and set yourself a power target to avoid costly mistakes.

    ECU mapping should help to fully realize the full potential of all the modifications you've done to your EZ30.

    (In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

    It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but your results usually depend much on the modifications you've done and the condition of your engine.

    Pulling air into your EZ30 is the aim to any engine upgrade task.

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

    Structure and flow rate of the Plenum can make a large change to fuel atomisation and engine efficiency on the EZ30.

    Commonly we find the intake manifold are in desperate need of motorsport parts, although some OEM provide fairly well optimized intake manifold.

    Big valve conversions on the EZ30, getting port matching and head flowing will also increase bhp and torque, the fantastic side effect is it will make space for a better bhp and torque increase on other parts.

    EZ30 Turbo upgrades

    NA (naturally aspirated) 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 EZ30

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

    If your motor has forced induction tuning mods are relatively easy and most turbo engines use more solid components.

    There are reliable limits for every engine, with some being extremely strong and some only just able to handle stock powerSee where you'll find these limitations and upgrade to better quality crank and pistons to survive the power.

    We've seen tuners spending a a stack of money on turbo charger upgrades on the EZ30 only to have the engine literally blow up on it's first outing after it's been completed.

    Big upgraded turbochargers often suffer low end lag, and smaller turbochargers spool up more quickly but won't have the high rpm engines power gains.

    In recent times the range of turbos is always developing and we now see variable vane turbos, allowing the vane angle is altered according to speed to lower lag and increase top end bhp and torque.

    Twin scroll turbos divert the exhaust flow into 2 channels and direct these at differently angled vanes in the turbocharger. They also boost the scavenging effect of the engine.

    It is common that there's a limitation in the air flow sensor (AFM/MAF/MAP) on the EZ30 when loads more air is being drawn into the engine.

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

    Adding a supercharger or additional turbo will make large bhp and torque gains, although more difficult to configure. We have this article covering twinchargers if you want to read more.

    Fuelling

    When you raise the power you will need to increase to the fuel system.

    More power needs more fuel. It is important to be generous with your injectors flow rate.

    The accepted safe increase is to add 20% when specifying an injector, this allows for injector deterioration and provides 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.

    EZ30 Performance Exhausts

    You only need to uprate your exhaust if your current exhaust is actually creating a restriction.

    On most factory exhausts you'll find the exhaust 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 equal out the flow of gases through the engine.

    But if your exhaust is too large, ie: it's over 2.5 inches bore, you will lose much of the exhaust flow rate and end up losing power and torque.

    Common exhaust restrictions can be traced to the catalyst installed, so adding a better flowing sports alternative is the answer. This keeps the car road legal and will flow much better due to it's higher internal surface area and design, so has the added benefit of keeping your car road legal. The alternative decat should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars..

    Weak spots, Issues & problem areas on the EZ30

    The EZ30 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

    Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

    Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

    Regular oil changes are vital on the EZ30, especially when tuned and will help extend the life and reliability of the engine.

    If you would like to know more, or just get some friendly advice on Tuning your EZ30 engine please join us in our car forums where you can discuss EZ30 tuning options in more detail with our EZ30 owners. It would also be worth reading our unbiased Subaru tuning articles to get insights into each modification and how effective they will be for your car.

    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 upgrades work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these EZ30 tuning guides which get regular updates and revisions.

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