Fiat Firefly N4 Tuning

"All you need to know about tuning and performance parts on the Fiat Firefly N4 engine!"

The Fiat Firefly N4 are good project engines and with a few sensible sports parts like ECU maps, turbo upgrades and camshafts you will substantially improve your driving experience.

In this article we examine Firefly N4 tuning and report on the greatest mods that work.

History, Power & Specs of the Firefly N4 Engine

Also known as the FCA Small Global or GSE engine this range had a modular design allowing Fiat to offer it in a variety of power levels and states of tune.


  • 101 PS (74 kW; 100 hp) at 6000 rpm (109 PS (80 kW; 108 hp) at 6250 rpm)
  • 134 Nm (99 lbft) at 3500 rpm (139 Nm (103 lbft) at 3500 rpm)


  • Fiat Uno
  • Fiat Argo
  • Fiat Cronos

Tuning the Fiat Firefly N4 and best Firefly N4 performance parts.

Best Firefly N4 tuning mods

When talking about the best modifications for your Firefly N4 engine, we are going to focus on the tuning parts that give the best value for money.

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 power band gains are on offer for camshaft upgrades.

Fast road cams usually boost the performance through the rpm band, you might lose a little bottom end torque but the higher rpm power will be better.

Motorsport cams, boost 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 should ideally to match your engines power to your usage of the car.

I'd be surprised if you have found a Firefly N4 Race camshaft is a pleasure to live with when driving in heavy traffic. The low end idle will be very lumpy and irregular, so something you would notice on a track when you drive in the upper third of the rpm band, but on roads this is a serious issue and we've heard from lots of drivers lamenting their decision to add an extreme competition cam profile to their engine.

Each engine responds better to different camshaft durations so view each engine as unique.

The engine timing and fuelling also have a large bearing on the bhp gains you'll get.

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

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

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

    Carefully think through your options and then source your parts and set yourself a power target to avoid disappointment.

    Mapping will help release the full potential of all the upgrades you've done to your Firefly N4.

    (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 outcome will depend much on the upgrades you've carried out and the condition of your engine.

    Shoving more air into the Firefly N4 engine is the whole point to any tuning job.

    Intake manifolds flow the air from the air cleaner and allow it to be drawn into the engine cylinders.

    Structure and rate of flow of the Plenum can make a noticeable improvement to fuel delivery on the Firefly N4.

    We often see manifolds are ripe for aftermarket parts, although some OEM provide fairly well optimized headers.

    Larger Firefly N4 valves, doing a bit of port work and head flowing will also raise torque, this will afford you increasing the torque increase on other parts.

    Firefly N4 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 Firefly N4

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

    When your car has a turbocharger upgrades are relatively easy and you will discover turbo engines are made using strengthened components.

    There are tuning limits for every engine, with some being extremely strong and some just sufficiently able to handle stock powerResearch these limitations and upgrade to better quality components to survive the power.

    It's not unheard of guys spending a lots of money on turbo charger upgrades on the Firefly N4 only to suffer the humiliation of seeing the engine throw a rod soon after it's completed.

    Bigger upgraded turbo chargers tend to experience a bottom end lag, and small turbo chargers spool up quickly but won't have the peak rpm engines power gains.

    Over the last 20 years the market of turbo units is always improving and we now see variable vane turbo units, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

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

    It is not unusual that there's a restriction in the air flow sensor AFM/MAP on the Firefly N4 when a lot 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 limited performance at a much lower level.

    Adding a supercharger or additional turbo will make large performance gains, although more complex to get working. We have this feature on twinchargers if you want to read more.


    You will need to ensure that the engine is not starved of fuel so will have to look at the fuelling when you start extending past 20% of a performance increase.We strongly recommend you to over specify your injector capacity.

    As a rule of thumb add 20% when specifying an injector, this allows for 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.

    Firefly N4 Performance Exhausts

    You should look to uprate your exhaust if your exhaust is actually causing a flow problem.

    On most factory exhausts you should find that 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 balance the flow of gases through the engine.

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

    Usual exhaust restrictions can be located the catalyst and filters installed, so adding a better 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 Firefly N4

    The Firefly N4 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 Firefly N4, 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 Firefly N4 engine please join us in our car forums where you can discuss Firefly N4 tuning options in more detail
    with our Firefly N4 owners. It would also be worth reading our unbiased Fiat tuning articles to get insights into each modification and how effective they will be for your car.

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