Fiat 2.0 twin cam engines

"Guide to modifying the Fiat twin cam"

The Fiat twin cam design has featured in the winning car more than any other in the history of the world rally championship (as of 2017).

The optimum upgrades on an engine are in our opinion the ones that give the best power gain for you spend.

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

Altering your twin cam cam will make a dramatic difference to the engine torque. Choosing a higher performance cam profile raises the torque accordingly.

Engine power ranged from 106 bhp to 137bhp on the NASP engines, the turbocharged units produced 182bhp to 214bhp from the factory.

The Fiat twin cam engine as fitted to the 131 Abarth Rally version featured an innovative engine showing the potential of this great engine block.

It featured in many models including

  • Fiat Spider 2000/131/132
  • Fiat Argenta/Strada/Ritmo/Regata/Croma/Tipo/Tempra/coupĂ©;
  • Lancia Beta/Delta/Prisma/Dedra/Thema,
  • FSO Polonez

It has been supercharged, turbocharged, fuel injection and there are many fans of this engine still quite active today. The Fiat Twin cam has, and rightly so, garnered a great following for itself.

The Twin cam design, fed by a double downdraught Weber 34 carburettor produced 137bhp at 6400rpm.

Tuning the fiat twin cam

You can't beat a decent Weber twin 40 setup pushing up power to around 140bhp. They may be fiddly to setup but when running right you get the perfect sweet spot.

Cam upgrades are the next best upgrade when you consider the power benefits to cost ratio.

Adding forced induction will make a much higher power gain, but you need to get the fuelling spot on.

Superchargers are easier to add than a turbocharger. If you want to add forced induction you need to adjust the compression ratio. A set of low compression pistons/crank will help achieve this aim.


Fast road cams tend to increase the performance over the rev range, you may sacrifice a little low end bhp but the high end rpm power will be lifted.

Head swaps are worth considering as some engines were designed to produce more power from the factory and head design was one of the most significant differences.

Check that the starter motor will still fit and everything lines up with the gearbox.

Whilst you have the head off it's well worth getting it flowed, ported and polished. A 3 or 5 angle valve job will assist with fuel atomization and build more low end torque.

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

In a daily driver must carefully try to optimize your bhp range to your preferences.

I would be surprised if you have found a Race camshaft is a pleasure to live with when driving in heavy traffic.

Different twin cam engines respond better to extreme camshaft durations check your engine on a rolling road.

The map and injectors and fuel pump also have an effect 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.

Stage 1 mods: Intake headers, Panel air filters, Sports exhaust manifold, Remaps/piggy back ECU, Drilled & smoothed airbox, Fast road camshaft.

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

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

The twin cam units are fantastic to work on and we see that there is a lot of parts and tuning parts out there.

Mapping allows a tuner to fully realize the full potential of all the tuning mods you've fitted to your twin cam.

It will usually give around 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 vital to any engine modification project to force air and fuel into the twin cam engine

Intake headers transmit the air during the suck phase from the intake filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

Structure and flow rate of the Intake headers can make a big effect on to fuel mixing and power on the twin cam.

Commonly we find the intake are begging for aftermarket parts, although a few OEM provide reasonably well designed intake.

Larger twin cam valves, doing some twin cam port enlargement and head flowing will also raise bhp, and importantly will raise potential for increasing the bhp increase on other tuning mods.

Turbo upgrades

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 twincam.

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.

However you will find an engines will have power limits

We recommend you find these limits and upgrade to higher quality components to cope with the power.

We've seen car owners spending a lots of money on turbocharger upgrades on the twin cam only to see the engine catastrophically fail just after it's finished.

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

the selection of turbochargers is always moving on and we now see variable vane turbochargers, permitting the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbochargers divert the exhaust gases into 2 channels and push these at differently angled vanes in the turbo. They also help the scavenging effect of the engine.

It is not unusual that there is a restriction in the air flow sensor AFM/MAP on the when loads more air is being fed into the engine.

We see 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 torque gains, although harder to install. We have a twincharger torque adding guide if you want to read more.


Don't miss you'll need to increase the fuel system when you are increasing the bhp and torque - it makes the car more thirsty.

The addition of fuel injection to these engines made a substantial difference to power and fuel economy.

Aftermarket solutions from Megasquirt and Haltech have been used effectively on the Fiat Twin Cam engines.

Don't forget to over specify your injectors flow rate.

The accepted safe increase is to add 20% when specifying an injector, this allows for injector deterioration and allows 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.

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
  • 58 PSI 682cc/min 400hp
  • 58 PSI 1022cc/min 600hp

4 Cylinder NASP engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp
  • 58 PSI 568cc/min 400hp
  • 58 PSI 853cc/min 600hp


You may need to uprate your exhaust if the current exhaust is actually creating a restriction.

On most factory exhausts you'll find 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.

Note that with the biggest exhaust you can buy this will slow up the exhaust flow rate - the best for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Common exhaust restrictions can be located the emissions filters installed, so adding a freer 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.

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 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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