Tuning the Hyundai Theta

"Building the best modified Hyundai Theta engine!"

Carref prides itself on providing the latest tips and guides to your modification project.

We shall review and look at Theta tuning and report on the optimum modifications for your car. Hyundai Theta make a good tuning project and with carefully chosen sports upgrades like remaps, turbo upgrades and camshafts you will really maximize your driving experience.

We review and look at Theta tuning and point out the ultimate modifications. Hyundai Theta offer good returns when tuned and with the right motorsport parts and mods.

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

• 2.0L (G4KA) 143 hp (140 lbft
• 2.4L (G4KC) 162 hp 164 lbft

Theta II

• 2.0L (G4KD) 163 hp 146 lbft
• 2.4L (G4KE) 176 hp 168 lbft

There were a few turbo variants of the Theta II

• 2.0L MPI turbo 223 hp  223 lbft
• 2.0L GDI turbo 274 hp 269 lbft
• 2.0L GDI turbo 271 hp  260 lbft
• 2.0L GDI turbo 255 hp 260 lbft

The Theta engine found it's way into the following models.

Theta/Theta-II (2.0L)

2.0L DOHC engine in a Kia (G4KD)
(G4KA, G4KD)

• Hyundai ix35 (2010-present)
• Hyundai Sonata (2011–2014)
• Kia Forte (2009-2013)
• Kia Rondo (2007-present)

Theta/Theta-II (2.4L)

(G4KC, G4KE, G4KG, G4KJ)

• Hyundai Santa Fe (2010-present)
• Hyundai Sonata (2006–2010)
• Hyundai Sonata GDI (2011-present)
• Hyundai Sonata (2011-2019) (Middle East)
• Hyundai Starex (2007-present)
• Hyundai Tucson (2010-present)
• Kia Cadenza GDI (2011-present)
• Kia Forte (2010-2013)
• Kia Optima (2006–2010)
• Kia Optima GDI (2011-present)
• Kia Rondo (2007-present)
• Kia Sportage (2011-present)
• Kia Sorento (2011-present)

Theta-II 2.0 Turbo (2.0T)

2011 Hyundai Sonata Limited 2.0T, turbo GDI engine
(G4KF, G4KH, G4KL)

• Genesis G70 GDI (2019-present)
• Hyundai Genesis Coupe (2009-2014)
• Hyundai i30N GDI (2019-present)
• Hyundai Santa Fe (Sport) GDI (2013-present)
• Hyundai Sonata GDI (2011–2014)
• Hyundai Veloster N GDI (2019–present)
• Kia Optima GDI (2011-present)
• Kia Sorento GDI (2016-present)
• Kia Sportage GDI (2011-present)
• Kia Stinger GDI (2018-present)

What are the most effective Theta modifications

The best tuning parts on an engine are in our opinion the ones that give the biggest return for your cash.

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

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

Fast road camshafts normally increase the torque across the rev range, you might lose a little low down torque but your higher rpm power will be better.

Race camshafts, 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 must carefully try to match your engines power to your preferences.

I'd be gobsmaked if you find a Motorsport cam is a pleasure to live with when driving around busy urban areas.

Different Theta engines respond better to extreme cam durations than others.

The ECU mapping and fuelling also will make differences on the power gains you'll achieve.

Altering 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.

Please watch our introduction Video tutorial to car tuning. Be sure to subscribe and support our new channel.

Modifying to Stage 1:

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

Modifying to Stage 2:

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

Modifying to Stage 3:

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

Remaps should help to to establish the full potential of all the tuning mods you've done to your Theta.

It will usually give around 30% more power on turbocharged vehicles and 15% on NASP engines, but you mileage will vary depending on the tuning mods you've done and the condition of your engine.

It is the main goal to any engine modification job to feed air into the Theta engine

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

Design and flow characteristics of the Intake manifold can make a big difference to to fuel delivery on the Theta.

We often see air intake manifolds are crying out for an upgrade, although some manufacturers provide reasonably well designed air intake manifolds.

Larger Theta valves, doing some 3 or 5 angle valve jobs and porting and head flowing will also boost torque, this will make space for raising the torque 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 Theta

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

If the engine is fitted with a turbo upgrades are giving better power gains and we find turbo engines use many forged and stronger components.

However engines will have power limits

See where you'll find these limits and fit better quality crank and pistons to cope with the power.

We see many people spending a loads on turbo charger upgrades on the Theta only to watch the engine block literally blow up on it's first outing after it's used in anger.

Large capacity turbo units commonly experience a bottom end lag, and smaller turbo units spool up more quickly but won't have the top end power band gains.

Thankfully the world of turbos is always increasing and we now see variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end performance.

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

You'll commonly see there is a limit in the air flow sensor MAP/MAF/AFM on these engines when considerably 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 limited bhp and torque at a much lower level.

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

Fuelling

You will need to ensure that the engine is not starved of fuel so should look at the fuelling when you start going beyond 20% of a power increase.It makes sense to over specify your injector capacity.

The rule of thumb is to add another 20% when buying an injector, helps cope with 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 58 psi of fuel pressure at idle.

4 Cylinder turbocharged engines

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

4 Cylinder NASP engines

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

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 only need to to increase your exhaust if the current exhaust is creating a restriction.

On most factory exhausts you'll see your flow rate is still fine 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 generally help improve air flow out of the engine but avoid an exhaust that is too wide or you may end up will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Typically exhaust restrictions are in the catalyst and filters installed, so adding a higher flowing high performance alternative will help avoid this restriction.

Weak spots Issues & problem areas on the

The engines are generally reliable and solid as long as they are regularly serviced and maintained.

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

There was a recall back in 2014 on both the 2.0 and 2.4 liter engines due to a fault in the crankshaft manufacture where metal shards would restrict oil flow and caused premature wear on the bearings. The issue would initially manifest itself as a grinding noise/vibration.

For more information 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.

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 them on each model of car. Comments are used to improve the accuracy of these articles which are continually updated.

This article was written by Waynne Smith on TorqueCars, and I appreciate your feedback and suggestions. This entry was filed under Hyundai, Kia. You can leave a response below or join TorqueCars forum to discuss this article and car modification in detail with our members.

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out TorqueCars new YouTube channel, and see their awesome new content...