Alfa Romeo Boxer Tuning

"All you need to know about tuning and performance parts on the Alfa Romeo Boxer engine!"

The Alfa Romeo Boxer are popular tuning projects and with carefully picked performance parts like remaps, turbo kits and camshafts you will really maximise your driving opportunities.

The Alfa boxer engine sounds fantastic, and the early 1400 with double barrel carbs was an aural delight when the tuning was spot on.

In this article we provide a guide to Boxer tuning and point out the best mods that work.

History, Power & Specs of the Engine

This was a  flat 4 piston engine ideally suited to low engine bays, where power was required. It was replaced with the transverse Twin Spark units around 1996.

This successful engine enjoyed a 26 year production run, and saw fuel injection, 16v and quad cam versions in it's many refinements and upgrades.

The engine first appeared in 1971 as  1200cc unit, then by stroking the engine a 1300cc unit was released in 1977 and a 1351cc version 1978.

In October of 1986 we saw a 1500cc version of this engine which was even adopted by Nissan for the Cherry in Europe.

1600 -101hp

1700 -116hp

  • October 1986 – 1995 Alfa Romeo 33
  • October 1986 – 1989 Alfa Romeo Sprint

1700 16V -135hp

Bosch Motronic ML 4.1 ECU & fuel injection system.

Tuning the Alfa Romeo Boxer and best Boxer performance parts.

Best Boxer upgrades

When talking about the best top for your Boxer engine, we are going to focus on the parts that give the best power gain for you money.

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 torque gains are on offer for cam upgrades.

Fast road camshafts usually raise the bhp through the rpm band, you may lose a little bottom end bhp but the high end rpm power will improve.

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

A Race cam is not great in heavy traffic.

You should ideally match your bhp range to your preferences so for a typical daily driver stick with a fast road Boxer cam

Some Boxer engines respond better to less aggressive cam durations so set your engine up on a rolling road.

The ecu map and injectors and fuel pump also have an effect on the power gains you'll make.

Altering 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.

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

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

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

The Boxer power plant are great to work on and thanks to their popularity there are increasing numbers of modifications and tuning parts around.

Mapping should help to fully realize the full potential of all the mods you've fitted to your Boxer.

(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 NASP engines, but your results usually depend much on the mods you've applied and the condition of your engine.

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

Intake manifold transmit the air from the air cleaner and allow it to be sucked into the engine cylinders with fuel for the squish phase.

The size of bore and shape and rate of flow of the Air Intake manifolds can make a large change to fuel delivery on the Boxer.

On popular production engines intake are in dire need of aftermarket parts, although some makers provide reasonably good intake.

Big valve conversions on the Boxer, carrying out port work and head flowing will also boost torque, and significantly will give you increasing the torque increase on other modifications.

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 Boxer

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

If your car is turbo charged tuning mods are going to make more power and you will discover turbocharged engines will have harder and stronger components.

There are reliable limits for every engine, with some being extremely strong and some only just able to handle stock power

See where you'll find these limits and fit better quality components to cope with the power.

We've seen people spending a fortune on turbo upgrades on the Boxer only to experience the car explode just after it's completed.

Big capacity turbos tend to experience a bottom end lag, and little turbos spool up more quickly but do not have the top end power band gains.

Thankfully the market of turbo chargers is always increasing and we commonly find variable vane turbo chargers, permitting the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbo chargers divert the exhaust gases into two channels and feed these at differently angled vanes in the turbo. 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 these engines when a lot more air is being sucked into the engine.

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

Adding a supercharger or additional turbo will make large power gains, although harder to configure. We have this in depth look at twinchargers if you want to read more.


You will need to ensure that the engine is not starved of fuel so should increase the fuelling when you start exceeding 20% of a power increase.We would recommend you to be generous with your injectors flow rate.

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

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder turbocharged engines

  • 58 PSI 170cc/min 100hp
  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp

4 Cylinder NASP engines

  • 58 PSI 143cc/min 100hp
  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp


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

On most factory exhausts you'll see your flow rate is still good 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 gases through the engine.

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

Common exhaust restrictions come around the catalysts installed, so adding a freer flowing high performance aftermarket one will improve air flow, and rather than doing an illegal decat, will keep the car road legal.

Weak spots Issues & problem areas on the Boxer

The Boxer 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 Boxer, 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 Boxer engine please join us in our friendly forum where you can discuss tuning options in more detail with our worldwide members, or read our 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 mods work best for you on your car. Which helps us keep our guides and tips up to date helping others with their modified car projects. Your feedback and comments are used to keep this page up to date, and help improve the accuracy of these Boxer articles which are continually updated.

PLEASE HELP: I NEED YOUR DONATIONS TO COVER THE COSTS OF RUNNING THIS SITE AND KEEP IT RUNNING. I do not charge you to access this website and it saves most TorqueCars readers $100's each year - but we are NON PROFIT and not even covering our costs. To keep us running PLEASE Donate here

If you liked this page please share it with your friends, drop a link to it in your favourite forum or use the bookmarking options to save it to your social media profile.

Check out our new YouTube channel, we're regularly adding new content...


Please use our forums if you wish to ask a tuning question, and please note we do not sell parts or services, we are just an online magazine.

Help us improve, leave a suggestion or tip

Your Constructive comments on this article

Member Benefits

Join our forum today and benefit from over 300,000 posts on tuning styling and friendly car banter.

You will also have full access to the modifed car gallery, project car updates and exclusive member only areas.

(All car owners of all ages and from all countries are welcome).

Popular articles

Diesel tuning
ECU Remapping
Double Clutch
Safety mods
Induction Kits
Customize a car
Chipping cars
Modded Car insurance
Track day insurance cover
Remap Diesels
Calculate MPG
DPF cleaning

Engine Knock

How to avoid engine knock and pinging


Suspension settings, lowering and stiffening

Hydraulic Vs Air Suspension

Air or Hydraulic suspension kits

Split Bonnets

Creating a custom self opening split bonnet or split hood.

Vehicle Checks

How to check a vehicle

Irmscher Corsa

Latest Corsa Gets An Irmscher Make Over

MPG Calculator

MPG calculator UK miles per Gallon – calculate MPG