Tuning the Hyundai Sigma

"Building the best modified Hyundai Sigma engine!"

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

A humble V6 which ranged from 2.5 to 3.5L capacity thanks to changes to both bore and stroke.

Most versions had a DOHC but there were SOHC heads used in the Sigma range.

We review Sigma tuning and point out the best modifications. Hyundai Sigma great bases for a tuning project and with carefully chosen tuning upgrades like a remap, turbo upgrades and camshafts you will greatly enhance your driving pleasure.

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

  • 2.5D G6AV DOHC 160 hp at 6000 rpm 150 lbft at 4500 rpm
  • 3.0D G6AT SOHC 158 hp  at 5000 rpm 177 lbft at 3000 rpm
  • 3.0D G6AT DOHC 182 hp  at 6000 rpm 178 lbft at 4500 rpm
  • 3.0D G6CT DOHC 189 hp  at 6000 rpm 192 lbft at 4000 rpm
  • 3.5D  G6AU DOHC 200 hp at 5500 rpm 214 lbft at 4800 rpm
  • 3.5D G6CU DOHC 217 hp  at 5500 rpm 232 lbft at 3500 rpm

What are the most effective Sigma mods

Just because a tuning parts is popular with Sigma owners it doesn't mean you should fit it, instead we'll focus tuning parts that will give your Sigma the best power gain for you money.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake and exhaust durations will alter depending on the chosen camshaft profile, so large engines power gains are on offer for camshaft upgrades.

Fast road camshafts commonly push up the performance over the rpm band, you may lose a little low down torque but high end rpm power will be higher.

Motorsport camshafts, push up the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers especially on a 6000rpm v6 like the Sigma.

In a car used daily must carefully try to match your engines power to your preferences.

I'd be surprised if you have thought a Motorsport and race camshaft is a pleasure to live with when in heavy traffic.

Some Sigma engines respond better to less aggressive camshaft durations check your engine on a rolling road.

The ecu map and fuel pump and injectors also will make differences on the torque gains you'll get.

Extending exhaust or intake durations can alter the torque 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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:

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

Modifying to Stage 2:

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

Modifying to Stage 3:

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

The Sigma engine blocks respond well to upgrades and we see that there are plenty of upgrades and tuning parts around.

ECU flashing allows a tuner to to establish the full potential of all the parts you've done to your Sigma.

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

It is the main goal to any engine modification task to feed air into each cylinder

Headers flow the air from the filter and allow it to be drawn into the engine and mixed with fuel.

The bore size, shape and flow rate of the Headers can make a substantial effect on to fuel mixing and power on the Sigma.

On popular production engines air intake manifolds are ripe for an upgrade, although a few makers provide fairly well optimized air intake manifolds.

Big valve conversions on the Sigma, doing some Sigma port enlargement and head flowing will also lift bhp, and significantly will afford you a greater bhp increase on other tuning mods.

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 Sigma

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 your motor has a turbocharger modifications are simpler to install and turbocharged engines already contain stronger components.

However you'll find engines have limits

Research these restrictions and fit higher quality crank and pistons to handle the power.

We see many guys spending a a stack of money on turbo charger upgrades on the Sigma only to suffer the indignity of watching the engine explode when it's been enthusiastically driven.

Large upgraded turbos commonly experience a bottom end lag, and smaller turbos spool up much more quickly but don't have the high rpm engines power gains.

Thankfully the range of turbo chargers is always developing and we are seeing variable vane turbo chargers, where the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust gases into two channels and flow these at differently designed vanes in the turbo charger. They also boost the scavenging effect of the engine.

It is common that there's a limitation in the air flow sensor AFM/MAF on these engines 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 limited torque at a much lower level.

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


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

The rule of thumb is to add 20% capacity when specifying an injector, this allows for injector deterioration and provides you 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.

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.

Only look to boost your exhaust if the current exhaust is creating a restriction.

On most factory exhausts you should find that the exhaust flow rate is still 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 increase the flow of air through the engine.

But if your exhaust pipe is too big, ie: over 2.5 inches bore, you will lose a great deal of your flow rate and end up lacking power and torque.

Usual exhaust restrictions can be traced to the emissions filters installed, so adding a better flowing race 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.

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 tuning parts work best for them on each model of car. Comments are used to improve the accuracy of these articles which are continually updated.

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