BMW B37 Tuning

"All you need to know about tuning and performance parts on the BMW B37 engine!"

This pages aim is examine the options for your B37 tuning and report on the best modifications for your car. BMW B37 make awesome project engines and with a few sensible tuning parts like remapping, turbo upgrades and camshafts you will really maximize your driving enjoyment.

The B37 is a pretty strong unit, thanks in part to the forged components used. It has VANOS, Valvetronic, a clever electric water pump to maintain engine temps and allow a fast warm up and meets the stringent EU6 emissions regulations.

The direct injection setup and turbo choices (a twin scroll turbo) minimises lag and allows some pretty high boost settings, and still burns very cleanly.

Typical gains for a remap on your B37 would be a 30hp gain with no other mods, and you could see 50bhp more if you added an induction kit, exhaust headers and DPF removal (if legal in your area.)

History, Power & Specs of the B37 Engine

This is an interesting engine design, as it uses a small 3 cylinder engine with a single, mono-scroll and VTG turbocharger ideally suited for small cars models like the mini, it still manages to pack a serious punch of power.

B37C15K0

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

B37C15U0

  • 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)

Tuning the BMW B37 and best B37 performance parts.

Best B37 engine upgrades

When talking about the ultimate modifications for your B37 engine, we are going to concentrate on the parts that give the best power gain for you spend.

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

Fast road cams usually boost the power throughout the rev range, you could drop a little low down power but the high end rpm power will be better.

Motorsport and race cams, boost 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 daily driver must carefully try to match your torque band to your driving style.

I'd be completely gobsmacked if you have found a B37 Race camshaft is a pleasure to live with when driving around busy urban areas. This is because a competition cam causes a very lumpy idle, and makes the car more prone to stall or jerk along in stop start traffic, sadly though many ignore this and end up ruining a perfectly good car and having to revert back to a fast road, or OEM cam profile.

Some B37 engines respond better to less aggressive cam durations so set your engine up on a rolling road.

The direct injection setup and turbo choices (a twin scroll turbo) minimises lag and allows some pretty high boost settings, and still burns very cleanly.

Typical gains for a remap on your B37 would be a 30hp gain with no other mods, and you could see 50bhp more if you added an induction kit, exhaust headers and DPF removal (if legal in your area.)

The engine timing and fuelling also will make differences on the power gains you'll achieve.

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

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

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

The B37 power trains are great to work on and thankfully there are increasing numbers of mods and performance parts out there.

A remap will help release the full potential of all the mods you've done to your B37.

(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, but the end result may differ on the mods you've fitted and the condition of your engine.

Forcing air and fuel into each cylinder is vital to any engine modification project.

Intake flows the air during the suck phase from the air filter and allows it to be fed into the engine cylinders with fuel for the squish phase.

We have to mention the swirl flaps fitted to the B37, the theory behind BMW fitting these is to spiral the air into the cylinders helping the fuel to mix with the air more thoroughly.

The swirl flaps are only really effective at lower RPMs so it's more of an economy and emissions feature than a performance one.

As the EGR (exhaust gas recirculation) valve does it's thing oil residue builds up coating the intake with carbon, narrowing the intakes, and in some cases we've seen these lose 50% of their capacity to flow air.

When you add the EGR issues to the swirl flaps the problems just keep getting bigger, and instead of helping emissions and low RPM efficiency, it degrades it further.

So many owners are opting to remove the swirl flaps completely, but this may not be legal in some areas. The merits of doing so in our mind is questionable, as this could well lead to further carbon build up issues, so opting to upgrade the swirl flaps to a better made solution makes more sense.

Keep an eye out for symptoms of carbon build up in the intake.

The bore size, shape and flow rate of the Plenum can make a large improvement to fuel delivery on the B37.

We often see intake manifold are begging for motorsport parts, although some manufacturers provide well optimised intake manifold.

Larger B37 valves, doing some port matching and head flowing will also improve performance, the fantastic side effect is it will permit an improved performance increase on other tuning mods.

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 twin scroll turbo minimises lag, and is really efficient giving a decent top end, with a remap extracting around 30 to 50bhp more depending on supporting mods.

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.

However you will find an engines will have power limits and taking the car over 50bhp will certainly require a different upgraded turbo, with hybrid turbos proving quite popular.

We recommend you find these limitations and upgrade to more solid crank and pistons to cope with the power.

We see many mechanics spending a lot of money on turbo charger upgrades and then having the engine go into limp home mode or misfiring. Thankfully this is quite rare as the B37 engines are well built but if a turbo is not correctly mapped, or your fuelling is wrong you will experience problems.

Big upgraded turbochargers commonly suffer a bottom end lag, and smaller turbochargers spool up much more quickly but don't have the peak rpm bhp gains.

Thanks to new tech the world 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 performance.

Twin scroll turbochargers divert the exhaust flow into two channels and push these at differently angled vanes in the turbo charger. They also improve the scavenging effect of the engine.

You'll commonly see there is a limit in the air flow sensor AFM/MAF on the B37 when considerably more air is being fed into the engine.

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

Adding a supercharger or additional turbo will make large torque gains, although more difficult to configure. We have this feature on twinchargers if you want to read more.

B37 Fuelling upgrades

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

More torque requires more fuel, you can't just push more air into the engine.

It makes sense to be generous with your flow rate on the injectors.

The accepted safe increase is to add 20% when fitting an injector, this accounts for injector deterioration and gives 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.

B37 performance exhausts

You should look to replace your exhaust if your exhaust is actually causing a restriction in flow.

On most factory exhausts you'll see the flow rate is still fine even on modest power gains, but when you start pushing up the power levels you will need to get a better flowing exhaust.

Bear in mind that diesel engines do not run high RPM's compared with petrol engines, so there is not much of a gain to be had. However improving air flow in the exhaust header and DPF in particular will generally release another 10-20bhp.

Diesel exhausts, and the B37 is no exception, tend to flow really well. You'll only usually see a gain with a performance exhaust header on the B37.

Don't go with the largest exhaust you can find you'll slow up the exhaust flow 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.

Common exhaust restrictions are in the catalysts installed, so adding a faster flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots, Issues & problem areas on the B37

The B37 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 B37, 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 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.

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 B37 articles which are continually updated.

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