Modding upgrading and tuning the BMW M90 engine!

All you need to know about "M90 Modifications"

How to modify and upgrade the BMW M90

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

Forums like the one at TorqueCars are frequently seeing threads requesting information on how to improve the M90 from people inquiring about getting more power from the M90 and wanting to know what are the best tips for M90 power upgrades. So let us look into BMW M90 parts and outline the best modifications on this great engine and point out some problems along the way.

Car Tuning Tips will consider M90 tuning and report on the best mods that work. BMW M90 are good project engines and with the right tuning upgrades like remapping, turbo upgrades and camshafts you will substantially improve your driving pleasure.

Just because particular parts are popular with M90 owners it doesn't mean its worth having, we will focus on the best parts that will give your M90 the best power gain for you spend.

Without us subscribing to the popular myth of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

M90 induction kits

Improving air intake on the M90

You need fuel and air for an engine to work. If there is too little fuel then it will run lean, if there is too little air it runs rich sapping power . We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the whole point to any engine performance tuning project to get air into the M90 engine but this has a knock on effect with the air flow sensor.

You'll commonly see there's a limitation in the air flow sensor AFM/MAP on the M90 when considerably more air is being fed into the engine.

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

Intake take the during the engines suck phase from the filter and allow it to be pulled into the engine and mixed with fuel.

Structure and flow characteristics of the Headers can make a large difference to to fuel mixing and power on the M90.

It's not uncommon that plenum chambers are ripe for motorsport parts, although a few car makers provide well optimised plenum chambers.

Larger M90 valves, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also boost bhp and torque, & importantly will permit a better bhp and torque increase on other tuning mods.

M90 performance cam tips.

Some M90 engines respond better to more aggressive camshaft durations so view each engine as unique.

The map and fuel pump and injectors also have a large bearing on the bhp gains you'll get.

Extending exhaust or intake durations 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.

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 commonly push up the bhp through the rev band, you may lose a little low end power but the top end will be lifted.

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

On a daily driver you must carefully try to optimize your engines power to your preferences.

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

Stage 1, 2 and 3 mods for the M90

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 M90 parts:

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

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 2 M90 parts:

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

Stage 3 M90 parts:

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

The M90 engine blocks respond well to mods and we're finding that there is an increase of modifications and performance parts about.

A remap should help to fully realize the full potential of all the tuning mods you've done to your M90.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output will rely on the tuning mods you've carried out and the condition of your engine.

Turbo modifications on the M90

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the 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 massive power gains.

If the engine has a turbo already fitted modifications are simpler to install and turbo charged engines are made using harder and stronger components.

However most engines will need better parts at higher power limits

Discover these limits and install higher quality crank and pistons to survive the power.

It's not unheard of car owners spending a a stack of money on turbo charger upgrades on the M90 only to see the car explode on it's first outing after it's completed.

Bigger capacity turbo units commonly experience a bottom end lag, and little turbo units spool up quickly but do not have the high rpm power band gains.

Thankfully the market of turbochargers is always improving and we now see variable vane turbochargers, permitting the vane profile is altered according to speed to lower lag and increase top end bhp.

Twin scroll turbochargers divert the exhaust gases into a couple of channels and flow these at differently profiled vanes in the turbocharger. They also boost the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large performance gains, although harder to get working. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the M90

You will need to ensure that the engine is not starved of fuel so will need to pay attention to the fuelling when you start extending past 20% of a bhp and torque hike. It is important to be generous with your injectors flow rate.

The accepted safe increase is to add 20% when fitting an injector, this allows for injector deterioration and provides a little spare capacity should the engine need more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended M90 performance exhaust upgrades

Only look to uprate your exhaust system with an upgraded one is if the current exhaust is actually creating a restriction.

On most factory exhausts you'll find the flow rate is still ok even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Sports exhausts equal out the flow of air through the engine.

But if your exhaust is too large, ie: it's over two and a half inches diameter, you will lose much of the exhaust flow rate and end up lacking power and torque.

Typically exhaust restrictions are in the catalyst and filters installed, so adding a faster flowing performance alternative will help avoid this restriction.

Catalyst removal (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the M90

Like most engines an M90, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the M90, failure to do this will exacerbate engine wear, on a tuned M90 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your M90 why not pop over to the forums at TorqueCars where you can chat about M90 tuning options and read about others projects who may be planning to do similar modifications on their M90.

We need your help to complete and improve this page, so do give us your feedback in the comments box below.

We want to know your experiences with modifications on your M90, it helps us improve our tips and keeps us current so please use the comments box to drop a tip.

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 TorqueCars new YouTube channel, and see their awesome 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