Fiat Firefly T4 Tuning

"All you need to know about tuning the Fiat Firefly T4 engine!"

The Fiat Firefly T4 are awesome to work on and with the optimum modified mods like a remap, turbo kits and camshafts you will definitely increase your driving fun.

TorqueCars will examine Firefly T4 tuning and show the optimum modifications for your car.

History, Power & Specs of the Firefly T4 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.


  • 150 PS (110 kW; 148 hp) at 5500 rpm 270 Nm (199 lbft) at 1850 rpm
  • 180 PS (132 kW; 178 hp) at 5750 rpm 270–285 Nm (199–210 lbft) at 1850 rpm


  • Jeep Renegade FL
  • Fiat 500X FL

T4 4xe PHEV

  • 190 PS (140 kW; 187 hp) at 5500 rpm 213 Nm at 1850 rpm
  • 240 PS (177 kW; 237 hp) at 5750 rpm 270 Nm (199 lbft) at 1850 rpm


  • Jeep Renegade 4xe
  • Jeep Compass 4xe

Tuning the Fiat Firefly T4 and best Firefly T4 performance parts.

Best Firefly T4 tuning mods

The best Firefly T4 upgrades on an engine are usually the ones that give the biggest return for your cash.

We won't be swayed by popular Firefly T4 upgrades, they need to be cost effective.

Altering your Firefly T4 cam will make a dramatic difference to the engine power band. Choosing a higher performance cam profile raises the power band accordingly.

Fast road camshafts commonly increase the torque throughout the rev band, you may lose a little bottom end torque but high end rpm power will be lifted.

Motorsport and race camshafts, increase the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport and race cam will just annoy you whilst driving around busy urban areas. This is because a competition cam causes a very lumpy idle, and makes the car more prone to stall or jerk along in stop start traffic, sadly though many ignore this and end up ruining a perfectly good car and having to revert back to a fast road, or OEM cam profile.

You should ideally optimize your power band to your usage of the car so for a car driven daily stick with a fast road Firefly T4 cam

Each engine responds better to mild cam durations check your engine on a rolling road.

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

A longer valve duration 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 Firefly T4

    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.

Fiat Firefly T4 Tuning Stages

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

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

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

The Firefly T4 engine blocks respond well to upgrades and we're finding that there are increasing numbers of upgrades and performance parts out there.

Remaps allows a tuner to establish the full potential of all the upgrades you've done to your Firefly T4.

(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 mileage usually rely on the upgrades you've applied and the condition of your engine.

It is the whole point to any tuning job to force more fuel and air into each cylinder

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

The size of bore and shape and flow characteristics of the Intake manifold can make a substantial change to fuel atomisation on the Firefly T4.

On popular production engines air intake manifolds are in desperate need of performance upgrades, although a few manufacturers provide reasonably well designed air intake manifolds.

Adding a Firefly T4 larger valve kit, carrying out 3 or 5 angle valve jobs and porting and head flowing will also improve torque, & importantly will allow you to get a better torque increase on other modifications.

Firefly T4 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 T4

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

When your motor has a turbo already fitted upgrades are going to net you a larger power gain and you'll see that turbocharged engines already contain strengthened components.

There are common areas of failure for every engine, with some being incredibly solid and some only just able to handle stock powerWe recommend you find these restrictions and fit more solid crank and pistons to utilize the power.

We see many people spending a lots of money on turbo upgrades on the Firefly T4 only to have the engine catastrophically fail on it's first outing after it's been completed.

Big capacity turbochargers often experience a bottom end lag, and small turbochargers spool up much more quickly but do not have the peak rpm torque gains.

Thankfully the world of turbochargers is always evolving and we are seeing variable vane turbochargers, allowing the vane profile is altered according to speed to lower lag and increase top end bhp.

Twin scroll turbochargers divert the exhaust gases into 2 channels and feed these at differently profiled vanes in the turbo charger. They also boost the scavenging effect of the engine.

It is not unusual that there is a restriction in the air flow sensor MAP/MAF/AFM on the Firefly T4 when considerably 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 bhp at a much lower level.

Adding a supercharger or additional turbo will make large bhp gains, although more difficult to setup. We have this article on twincharging if you want to read more.


Don't forget to uprate the fuel delivery when you are increasing the power - it makes the car more thirsty. Most tuners we speak with say to be generous with your flow rate on the injectors.

The rule of thumb is to add 20% to the flow rate when buying an injector, this accounts for injector deterioration and gives you some spare capacity should the engine need 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 T4 Performance Exhausts

You may need to replace your exhaust if your current exhaust is actually causing a restriction in flow.

On most factory exhausts you'll see 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 balance the flow of gases through the engine.

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

Common exhaust restrictions come around the catalysts installed, so adding a higher 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 Firefly T4

The Firefly T4 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 T4, 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 T4 engine please join us in our car forums where you can discuss Firefly T4 tuning options in more detail
with our Firefly T4 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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