Tuning the BMW B48

"Comprehensive guide to performance tuning the BMW B48 engine!"

Herein we examine the options for your B48 tuning and report on the ultimate mods that work. BMW B48 really good project engines and with carefully picked sports enhancements like remaps, turbo kits and camshafts you will definitely maximise your driving opportunities.

Just because particular mods are are common on B48 it doesn't mean it is good, we will recommend only what we regard are the best mods that will give your B48 the best value for money to power increase.

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 normally bump the performance through the rev band, you could sacrifice a little low end bhp but your top end will be higher.

Motorsport and race cams, bump the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Competition camshaft makes it harder when driving in heavy traffic.

You should ideally match your engines power to your cars usage so for a daily driver stick with a fast road B48 camshaft

Each engine responds better to extreme cam durations check your engine on a rolling road.

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

Extending exhaust or intake 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.

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

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

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

The B48 power trains make great tuning projects and thankfully there are increasing numbers of mods and tuning parts out there.

ECU mapping will help to establish the full potential of all the tuning mods you've fitted to your B48.

It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but figures achieved may vary depending on the tuning mods you've carried out and the condition of your engine.

Getting air and fuel into your B48 is the whole point to any car tuning project.

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

The size of bore and shape and rate of flow of the Air Intake manifolds can make a noticeable effect on to fuel mixing and power on the B48.

I usually find air intake manifolds are in dire need of aftermarket parts, although some manufacturers provide well optimised air intake manifolds.

Larger B48 valves, doing a bit of B48 port enlargement and head flowing will also boost bhp and torque, and significantly will make space for increasing the bhp and torque 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 B48

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 motor has a turbo already fitted mods are simpler to install and turbocharged engines use uprated components.

However you will find an engines have weakspots

We recommend you find these limitations and fit better quality crank and pistons to handle the power.

We see many guys spending a fortune on turbo upgrades on the B48 only to see the engine block literally blow up soon after it's first rolling road session.

Bigger turbo chargers tend to suffer low end lag, and small turbo chargers spool up more quickly but won't have the top end engines power gains.

Thanks to new tech the choice of turbos is always moving on and we now see variable vane turbos, allowing the vane angle is altered according to speed to lower lag and increase top end power.

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

It is common that there is a limit in the air flow sensor MAP/MAF/AFM on the B48 when a lot more air is being drawn into the engine.

We see 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 setup. We have this article on twincharging if you want to read more.

Fuelling upgrades and mods

When you improve the performance you will need to pay attention to to the fuel system.

More performance needs more fuel. It is important to be generous with your injector capacity.

The rule of thumb is to add 20% capacity when specifying an injector, helps cope with injector deterioration and affords 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.

Exhaust upgrades and mods

You only need to to increase your exhaust if your exhaust is actually creating a restriction in flow.

On most factory exhausts you'll see your 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.

Don't go with the largest exhaust you can source 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.

Usual exhaust restrictions come around the catalysts installed, so adding a freer flowing high performance alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the B48

The B48 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the B48, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your B48 engine please join us in our friendly forum where you can discuss tuning options in more detail with our tuning articles to get a full grasp of the benefits and drawbacks of each modification.

History of the Engine

The B48 shares much with the N20 which it was based on and also came with double VANOS Valvetronic and a twin scroll turbo.

  • 181 hp @5,000–6,500 rpm 290Nm 214 lbft @1,350–4,250 rpm
  • 189 hp @4,700–6,000 rpm 280Nm 207 lbft @1,250–4,500 rpm
  • 221 hp @5,000–6,500 rpm 310Nm 229 lbft @1,400–5,000 rpm
  • 228 hp @5,000–6,500 rpm 300Nm 221 lbft @1,250–4,800 rpm
  • 248 hp @5,200–6,500 rpm 350Nm 258 lbft @1,450–4,800 rpm
    255 hp @5,000–6,500 rpm 400Nm 295 lbft @1,550–4,400 rpm
  • 302 hp @5,000–6,250 rpm 450Nm 332 lbft @1,750–4,500 rpm

Tuning the BMW B48 and best B48 performance parts.

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 upgrades were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our B48 guides and tips are kept up to date.

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