Tuning the BMW B37

"Comprehensive guide to performance tuning the BMW B37 engine!"

Herein we review and look at B37 tuning and summarise the best modifications for your car. BMW B37 are awesome to work on and with the optimum enhancements like remaps, turbo kits and camshafts you will dramatically enhance your driving enjoyment.

When talking about the best parts for your B37 engine, we are going to concentrate on the upgrades that give the best value for money.

Altering your B37 camshaft will make a dramatic difference to the engine torque. Choosing a higher performance camshaft profile raises the torque accordingly.

NB: Fast road camshafts commonly increase the torque through the rev band, you could sacrifice a little bottom end torque but the top end will improve.

Race camshafts, increase the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Race cam makes it harder when driving in heavy traffic.

You should ideally optimize your engines power to your driving style so for a car driven daily stick with a fast road B37 cam

Some B37 engines respond better to mild cam durations than others.

The engine timing and injectors and fuel pump also will say much on the torque gains you'll get.

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

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

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


Carefully think through your options and then buy your tuning mods and set yourself a power target to avoid wasting your time and money.


Mapping should help to fully realize the full potential of all the modifications you've done to your B37.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but power output will differs on the modifications you've carried out and the condition of your engine.

Shoving more fuel and air into each cylinder is the whole point to any performance tuning job.

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

Structure and flow rate of the Intake headers can make a noticeable difference to to fuel delivery on the B37.

Many mass produced engine intake are ripe for motorsport parts, although a few makers provide well optimised intake.

Increasing the B37 valve size, getting B37 port enlargement and head flowing will also improve performance, this will afford you raising the performance increase on other upgrades.

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 B37

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.

When your car is turbocharged, upgrades are relatively easy and you will discover turbo engines already contain strengthened components.

There are tuning limits for every engine, with some being very over engineered and some just sufficiently able to handle stock power

We recommend you find these limits and install stronger pistons, crank and engine components to utilize the power.

We see many drivers spending a a stack of money on turbo charger upgrades on the B37 only to watch the whole thing throw a rod on it's first outing after it's first rolling road session.

Larger capacity turbo units will usually suffer low end lag, and little turbo units spool up much more quickly but don't have the peak end bhp gains.

Over the last 20 years the selection of turbo units is always moving on and we now see variable vane turbo units, permitting the vane profile is altered according to speed to lower lag and increase top end torque.

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

It is common that there's a restriction in the air flow sensor AFM/MAF on the B37 when a lot more air is being sucked into the engine.

You'll see that 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 harder to configure. We have this in depth look at twinchargers if you want to read more.

Fuelling upgrades and mods

When you increase the torque you will need to uprate to the fuelling.


More torque needs more fuel. We strongly recommend you to over specify your injector capacity.

As a rule of thumb add another 20% when buying an injector, this allows for injector deterioration and allows 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.

Exhaust upgrades and mods

Only look to replace your exhaust if the existing exhaust is creating a restriction.

On most factory exhausts you should find that the 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.

Please dont run with the biggest exhaust you can buy this will slow the exhaust 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.

Typically exhaust restrictions are traced to the catalysts installed, so adding a higher flowing high performance alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the B37

The B37 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the B37, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your B37 engine please join us in our friendly forum where you can discuss tuning options in more detail with our B37 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 tuning parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our B37 guides and tips are kept up to date.

History of the Engine


  • 95 PS (70 kW) @ 4000 rpm (162 lbft) @ 1500 or 1750–2250 rpm


  • 116 PS (85 kW) @ 4000 rpm (199 lbft) @ 1750–2250 rpm

70 kW (95 PS)

  • F20LCI as 114d (from 11/2015)
  • F45 as 214d Active Tourer (from 03/2015)
  • F46 as 214d Gran Tourer (from 07/2015)
  • F56 (MINI) as MINI One D 3(from 03/2014)
  • F55 (MINI) as MINI One D 5 Door (from 10/2014)

85 kW (116 PS)

    • F20 as 116d (from 03/2015)
    • F20LCI as 116d (from 11/2015)
    • F20LCI as 116d ED (from 11/2015)
    • F21LCI as 116d (from 11/2015)
    • F21LCI as 116d ED (from 11/2015)
    • F45 as 216d Active Tourer (from 11/2014)
    • F46 as 216d Gran Tourer (from 03/2015)
    • F48 as X1 sDrive16d (from 10/2015)
    • F56 (MINI) as MINI Cooper D 3 Door (from 03/2014)
      F55 (MINI) as MINI Cooper D 5 Door (from 10/2014)
      F40 as 116d  (from 07/2019)


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