BMW B48 Tuning

"All you need to know about tuning the BMW B48 engine!"

The BMW B48 make awesome project engines and with the optimum uprated parts like remaps, turbo upgrades and camshafts you will greatly enhance your driving enjoyment.

The B48 engine has much in common to the N20 on which it was based on and also came with double VANOS Valvetronic and a twin scroll turbo.

Here we review B48 tuning and report on the ultimate modifications.

History, Power & Specs 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. The design is undersquare and it came with quite a range of power figures.

Most of the power differences are electronic rather than mechanical, with an overboost option on some models giving another 15lbft of peak torque.

The 302hp version came with revised internals, notably a stronger crank, larger bearings and pistons and the lower compression ration allows more boost from the larger turbo. These mods are good upgrades for the lower powered versions if you want to fit a larger 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.

Best B48 tuning mods

Just because particular tuning mods are are common on B48 it doesn't mean it is good, we shall optimum tuning mods that will give your B48 the best power gain for you spend.

Significant gains on the B48 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

Fast road camshafts commonly increase the bhp and torque through the rpm band, you may lose a little bottom end bhp but the high end rpm power will be higher.

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

A Competition camshaft won't do well if 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.

You should ideally match your bhp range to your cars usage so for a car driven daily stick with a shorter duration B48 camshaft

Different B48 engines respond better to extreme cam durations check your engine on a rolling road.

The ecu map and fuel pump and injectors also will say much on the torque gains you'll make.

Extending exhaust or intake 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.

Typical stage 1 mods often include: Remaps/piggy back ECU, Panel air filters, Intake headers, Sports exhaust manifold, drilled & smoothed airbox, Fast road camshaft.

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

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

Carefully think through your options and then acquire your mods and set yourself a power target to avoid disappointment.

Pushing fuel and air into each cylinder is vital to any performance tuning job.

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

Shape and flow characteristics of the Plenum can make a noticeable improvement to fuel atomisation and engine efficiency on the B48.

Most intake headers are improved through motorsport parts, although a few makers provide reasonably good intake headers.

Increasing the B48 valve size, carrying out B48 port enlargement and head flowing will also raise bhp and torque, and more importantly will raise potential for increasing the bhp and torque increase on other parts.

B48 mapping/flash and piggyback tuning boxes

remap allows a tuner to unlock the full potential of all the upgrades you've fitted to your B48 and should be the last finishing mod you do *(yes we know that no tuning project is ever really finished).

Piggyback ECU's seem to be the way to go on the B48 with popular offerings from JB4, Dinan Sport/Elite and bootmod3.

You can expect to see around 30-40hp with an improved map.

Aftermarket ECU's offer another route, where a more capable ECU takes over fuel/boost/timing etc and allows fine control over these parameters allowing you to fully extract every extra BHP from your mods.

Megasquirt has been used in a few of our member BMW tuning projects to good effect, but there are many other brands out there. We would recommend you source one with a knock sensor, as we consider this vital on a highly tuned engine.

(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 and you can expect to see around 15% on NASP engines, but the end result usually depend much on the upgrades you've carried out and the condition of your engine.


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 major power gains.

If your motor is fitted with a turbo parts are going to net you a larger power gain and you will discover turbocharged engines are made using uprated components.

There are common areas of failure for every engine, with some being extremely strong and some only able to handle stock power

Discover these restrictions and install better pistons and crank to handle the power.

We see many tuners spending a lot of money on turbo upgrades on the B48 only to have the engine go up in smoke soon after it's completed.

Larger upgraded turbochargers tend to experience low end lag, and little turbochargers spool up really quickly but don't have the peak end engines power gains.

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

Twin scroll turbo units divert the exhaust gases into 2 channels and direct these at differently profiled vanes in the turbo. They also improve the scavenging effect of the engine.

You'll commonly see there is a limitation in the air flow sensor AFM/MAF on these engines when a lot more air is being sucked 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 power gains, although more complex to configure. We have this feature on twinchargers if you want to read more.


Don't omit to look at the fuel system when you are increasing the bhp and torque - it makes the car more thirsty. It is important to over specify your flow rate on the injectors.

The rule of thumb is to add 20% when fitting an injector, this takes into account injector deterioration and allows a little 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.

Swapping out to higher octane fuel will give a power boost on the B48 as it will pick this up and adjust/trim the timing to suit.

All the following flywheel power targets will assume an injector duty cycle of 80% and a base of 58psi of fuel pressure at idle.

4 Cylinder turbocharged engines

  • 58 PSI 340cc/min 200hp
  • 58 PSI 511cc/min 300hp
  • 58 PSI 682cc/min 400hp
  • 58 PSI 1022cc/min 600hp

4 Cylinder NASP engines

  • 58 PSI 285cc/min 200hp
  • 58 PSI 426cc/min 300hp
  • 58 PSI 568cc/min 400hp
  • 58 PSI 853cc/min 600hp

4 Cylinder supercharged engines

  • 58 PSI 312cc/min 200hp
  • 58 PSI 468cc/min 300hp
  • 58 PSI 625cc/min 400hp
  • 58 PSI 937cc/min 600hp


You should look to upgrade your exhaust if the current exhaust is creating a restriction.

On most factory exhausts you'll find the exhaust flow rate is 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 can usually air flow out of the engine but avoid an exhaust that is too big or you might just stuff your flow rate and make things worse. So generally speaking, keep to a size of 1.5 to 2.5 inches for best results.

We see some sites recommending removing the cat from your B48 for a power gain, but in most regions this would be regarded as an off road mod only. Instead go for a better flowing sports catalyst for the same power gains as a decat, without all the legal issues you would pick up.

Typically exhaust restrictions can be traced to the catalysts installed, so adding a higher flowing performance catalyst removes the restriction. We note that performance cats perform similarly to decats and have the added benefit of keeping your car street legal, as decats or catalyst removal is illegal in most territories for road going cars.

Weak spots Issues & problem areas on the B48

The B48 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 B48, 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 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.

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One Response to “B48 Tuning”


    Y have a x2 sdrive 28i 2018 with downpipes, bms intake,2nd cat deleted, and DME TUNE FLASH MY DYNO NUMBERS 293HP 350 TORQUE

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