Tuning the BMW M90

"Comprehensive guide to performance tuning the BMW M90 engine!"

We often are getting emails asking about the ultimate M90 power upgrades. So let us look into BMW M90 upgrades and outline the best upgrades on this great engine and point out some frequent tuning mistakes along the way.

TorqueCars will review and look at M90 tuning and highlight the optimum modifications for your car. BMW M90 really good project engines and with the optimum sports modifications like a remap, turbo upgrades and camshafts you will substantially improve your driving fun.

When talking about the best parts for your M90 engine, we are going to focus on the ones that give the best power gain for you 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 torque gains are on offer for camshaft upgrades.

NB: Fast road cams tend to push up the performance through the rev band, you may lose a little low down bhp but high end rpm power will improve.

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

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

I'd be surprised if you have ever thought a M90 Motorsport and race cam is a pleasure to live with when driving around busy urban areas.

Different M90 engines respond better to extreme cam durations so set your engine up on a rolling road.

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

A longer valve duration 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.

M90 Tuning Stages

Stage 1 M90 modifications: Sports exhaust manifold, Fast road camshaft, Intake headers, Panel air filters, Remaps/piggy back ECU, Drilled & smoothed airbox.

Stage 2 M90 modifications: Ported and polished head, fuel pump upgrades, high flow fuel injectors, Fast road cam, Sports catalyst & performance exhaust, induction kit.

Stage 3 M90 modifications: Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger), Crank and Piston upgrades to alter compression, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Competition cam.

Review your options and then buy your mods and set yourself a power target to avoid costly mistakes.

ECU flashing allows a tuner to unlock the full potential of all the modifications you've done to your M90.

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 vary depending on the modifications you've carried out and the condition of your engine.

It is the main goal to any car tuning job to pull more fuel and air into the M90 engine

Air Intake manifolds transmit the air during the suck phase from the filter and allow it to be fed into the engine cylinders.

Structure and flow rate of the Plenum can make a large improvement to fuel atomisation on the M90.

On popular production engines intake are begging for motorsport parts, although some OEM provide decently flowing intake.

Increasing the M90 valve size, getting 3 or 5 angle valve jobs and porting and head flowing will also raise bhp, this will permit a greater bhp increase on other parts.

Turbo upgrades for the M90

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 M90

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.

When your car has a turbocharger tuning parts are going to make more power and you will discover turbo engines are built using uprated components.

However engines have limits

Discover these limits and upgrade to higher quality crank and pistons to cope with the power.

We've seen people spending a fortune on turbocharger upgrades on the M90 only to experience the engine catastrophically fail when it's first rolling road session.

Large upgraded turbos will usually suffer no power at low rpm, and little turbos spool up quickly but do not have the peak rpm engines power gains.

In recent times the choice of turbo chargers is always moving on and we commonly find variable vane turbo chargers, permitting the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbo chargers divert the exhaust gases into a couple of channels and feed these at differently designed vanes in the turbo charger. They also improve the scavenging effect of the engine.

You'll commonly see there's a restriction in the air flow sensor MAP/MAF/AFM on the M90 when loads more air is being drawn into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting bhp at a much lower level.

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

Uprating M90 fuel injectors

Don't overlook the need to increase the fuel delivery when you are increasing the bhp - it makes the car more thirsty. Most tuners we speak with say to over specify your injectors flow rate.

As a rule of thumb add another 20% when buying an injector, this accounts 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.

Best M90 performance exhausts

You should look to boost your exhaust if your exhaust is actually creating a restriction.

On most factory exhausts you'll find the exhaust 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 the exhaust is too big, ie: it's over 2.5 inches bore, you will lose much of your flow rate and end up sapping power and torque.

Common exhaust restrictions can be traced to the catalysts installed, so adding a faster flowing high performance alternative will help avoid this restriction.

Problems and issues to look out for on the M90

The M90 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the M90, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your M90 engine please join us in our friendly forum where you can discuss tuning options in more detail with our M90 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 to complete and improve this page, so do give us your feedback in the comments box below.

We really like hearing from our readers, and hearing about which tuning mods were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our M90 guides and tips are kept up to date.

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