Tuning the Fiat TwinCam

"Comprehensive guide to modifying and tuning the tuning and performance parts on the Fiat TwinCam engine!"

Let us look into TwinCam tuning and highlight the ultimate mods that work. Fiat TwinCam provide a fun base for your project and with the optimum uprated mods like ECU maps, turbo upgrades and camshafts you will substantially maximize your driving pleasure.

The greatest TwinCam tuning parts on an engine are typically the ones that give the best power gain for you spend.

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

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

NB: Fast road cams usually push up the bhp and torque through the rpm range, you may lose a little low end power but the higher rpm power will be better.

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

On a car driven daily you need to match your engines power to your typical driving style.

You'll never find a TwinCam Competition camshaft is a pleasure to live with when driving in heavy traffic.

Different TwinCam engines respond better to extreme cam durations so set your engine up on a rolling road.

The ECU mapping and fuelling also have an effect on the torque gains you'll hit.

Longer valve 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.

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

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

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

The TwinCam power trains are fantastic to work on and thanks to their popularity there are quite a few choices of mods and tuning parts about.

ECU flashing allows a tuner to release the full potential of all the tuning parts you've done to your TwinCam.

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.

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.

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

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your results will rely on the tuning parts you've fitted and the condition of your engine.

Pulling air into your TwinCam is the whole point to any engine performance tuning job.

Intake manifold transmit the air during the suck phase from the filter and allow it to be drawn into the engine cylinders.

The size of bore and shape and flow rate of the Intake manifold can make a noticeable improvement to fuel atomisation and engine efficiency on the TwinCam.

We often see intake manifold are begging for an upgrade, although some manufacturers provide reasonably good intake manifold.

Big valve conversions on the TwinCam, getting port matching and head flowing will also lift bhp and torque, this will allow you to get a greater bhp and torque increase on other parts.

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

If a car has forced induction tuning mods are going to net you a larger power gain and most turbo charged engines are made with more solid components.

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.

It is important to find these limits and install forged components to handle the power.

We've seen mechanics spending a lot of money on turbo charger upgrades on the TwinCam only to have the motor literally blow up on it's first outing after it's completed.

Big turbo units tend to experience no power at low rpm, and small turbo units spool up quickly but do not have the peak end engines power gains.

In the last 10 years the range of turbo units is always evolving and we are seeing variable vane turbo units, where the vane profile is altered according to speed to lower lag and increase top end bhp.

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

It is common that there is a limit in the air flow sensor AFM/MAF on the TwinCam when loads more air is being drawn into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting power at a much lower level.

Adding a supercharger or additional turbo will make large bhp and torque gains, although more complex to get working. We have this article on twincharging if you want to read more.

Fuelling upgrades and mods

When you increase the bhp you will need to look at to the fuelling.

More bhp needs more fuel. It is important to over specify your flow rate on the injectors.

The rule of thumb is to add 20% when fitting an injector, this takes into account injector deterioration and provides a little 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.

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.

Exhaust upgrades and mods

You only need to to boost your exhaust if your exhaust is actually causing a flow problem.

On most factory exhausts you'll see 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 can help balance the flow of air through the engine.

But if the exhaust is too big, ie: over 2.5 inches bore, you will lose much of the exhaust flow rate and end up sapping power and torque.

Typically exhaust restrictions can be located the catalysts installed, so adding a faster flowing sports alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the TwinCam

The TwinCam engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the TwinCam, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your TwinCam engine please join us in our friendly forum where you can discuss tuning options in more detail with our TwinCam owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

We need your help improving this article, so please send us your feedback in the comments box below and pass on any tips, points or facts we have wrong or have not covered.

We really like hearing from our readers, and hearing about which upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our TwinCam guides and tips are kept up to date.

History of the Engine

It featured in many models including

  • Fiat Spider 2000/131/132
  • Fiat Argenta/Strada/Ritmo/Regata/Croma/Tipo/Tempra/coupé;
  • 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.

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