Hyundai Smartstream Tuning

"All you need to know about tuning the Hyundai Smartstream engine!"

We shall examine the options for your Smartstream tuning and outline the best mods that work.

A Hyundai Smartstream  engine provides a fun base for your project and with carefully chosen performance parts like a remap, turbo improvements and camshafts you will dramatically maximize your driving experience.

History, Power & Specs of the Engine

The Smartstream was released in 2018 and comes as a straight 4/6 and V6 configuration and turbocharged versions were also produced, thanks to a lower compression ratio, and updating fuelling and mapping.

  • Smartstream G1.6 121 hp
    Hyundai Venue (2019–present)
  • Smartstream G1.6T 178 hp
    Hyundai Sonata (2019–present)
    Kia Optima/Kia K5 (DL3) (2019–present)
  • Smartstream G2.0 158 hp *(hybrid = 192hp)
    Hyundai Sonata (2019–present)
    Kia Optima/Kia K5 (DL3) (2019–present)
  • Smartstream G2.5 177hp
    Hyundai Azera (2019-present)
    Hyundai Sonata (2019–present)
    Kia Optima/Kia K5 (DL3) (2019–present)
  • Smartstream G2.5T 300hp
    Genesis GV80 (2020–present)
  • Smartstream G3.5T 375hp
    Genesis GV80 (2020–present)
  • Smartstream D3.0 274hp
    Genesis GV80 (2020–present)

Best Smartstream tuning mods

When talking about the best best for your Smartstream engine, we are going to focus on the tuning parts that give the best power gain for you spend.

Significant gains on the Smartstream can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the engines power and power output.

Fast road camshafts tend to raise the bhp across the rev band, you could sacrifice a little low down bhp but the top end will be lifted.

Motorsport and race camshafts, raise 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 cam won't do well if 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.

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

Different Smartstream engines respond better to more aggressive camshaft durations so view each engine as unique.

The map and fuelling also have a large bearing 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.

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Best Engine Mods for your car

  1. Engine Tunes - engine tuning/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.

Typical stage 1 mods often include: drilled & smoothed airbox, Intake manifolds, Fast road camshaft, Remaps/piggy back ECU, Sports exhaust header/manifold, Panel air filters.

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

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

Careful think through then find your modifications and set yourself a power target to avoid disappointment.

ECU flashing should help to release the full potential of all the parts you've fitted to your Smartstream.

(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 the end result usually vary depending on the parts you've fitted and the condition of your engine.

It is vital to any engine performance tuning job to shove more air and fuel into each cylinder

Intake manifold flow the air during the suck phase from the air cleaner and allow it to be sucked into the engine cylinders with fuel for the squish phase.

The bore size, shape and rate of flow of the Plenum can make a substantial difference to fuel engine efficiency on the Smartstream.

Commonly we find the intake manifolds are ripe for a performance upgrade, although a few makers provide well optimised intake manifolds.

Fitting big valve kits, getting port matching and head flowing will also increase performance, this will allow you to get raising the performance increase on other modifications.

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 Smartstream

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

When an engine is fitted with a turbocharger parts are going to make more power and turbo charged engines are built with strengthened components.

There are practical limits for every engine, with some being very over engineered and some just sufficiently able to handle stock power

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

There are many car owners spending a lot of money on turbocharger upgrades on the Smartstream only to see the engine block throw a rod when it's been finished.

Big turbo units often suffer no power at low rpm, and low capacity turbo units spool up really quickly but won't have the top end bhp gains.

We are pleased that the market of turbo units is always evolving and we commonly find variable vane turbo units, where the vane profile is altered according to speed to lower lag and increase top end torque.

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

You'll commonly see there is a restriction in the air flow sensor (AFM/MAF/MAP) on these engines when loads more air is being pulled into the engine.

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

Adding a supercharger or additional turbo will make large performance gains, although more challenging to configure. We have a twincharger performance adding guide if you want to read more.


Don't dismiss the need increase the fuel delivery when you are increasing the torque - it makes the car more thirsty. It is important to over specify your flow rate on the injectors.

The rule of thumb is to add another 20% when buying an injector, this takes into account injector deterioration and affords 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.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

We'll illustrate on the 4 cylinder engines how you need to match flow with power. The 6 cylinders will need less cc as each injector is only providing 1/6th of the fuel.

4 Cylinder turbocharged engines

  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp
  • 58 PSI 682cc/min 400hp

4 Cylinder NA (naturally aspirated) engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp


You may need to upgrade your exhaust if the current exhaust is actually creating a restriction in flow.

On most factory exhausts you'll see 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 usually air flow through the engine but avoid an exhaust that is too big or you might just stuff your flow rate and make things worse. So generally speaking, keep to a size of 1.5 to around 2.5 inches to maximise flow rates, and this should take into account the amount of air your engine is moving.

Usual exhaust restrictions can be located the emissions filters installed, so adding a higher flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots Issues & problem areas on the Smartstream

The Smartstream 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 Smartstream, 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 engine please join us in our friendly forum where you can discuss tuning options in more detail with our owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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