Modding uprating the BMW B48 engine!

Tuning guide "B48 Modifications"

B48 Modifications Guide

How to modify and upgrade the BMW B48

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

TorqueCars are regularly getting messages asking about how to improve the B48 from people wanting to know what are the things tuners are recommending when it comes to B48 upgrades. So let us look into BMW B48 upgrades and outline the best mods that work on this great engine and point out some potential pitfalls along the way.

The BMW B48 really good project engines and with the right tuning upgrades like remaps, turbo upgrades and camshafts you will positively enhance your driving opportunities.

We shall look at B48 tuning and summarise the ultimate modifications.

The optimum B48 tuning parts on an engine are obviously the ones that give the biggest return for your money.

We won't be swayed by popular B48 tuning parts, they need to be cost effective.

B48 induction kits

Improving air intake on the B48

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 losing power and potentially damaging the engine. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Pulling more fuel and air into your B48 is the aim to any performance tuning task.

It is common that there is a limit in the air flow sensor MAF/MAP on the B48 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 limited bhp at a much lower level.

Engines intake headers transmit the on the suck phase from the filter and allow it to be drawn into the engine and mixed with fuel.

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

On popular production engines intake headers are in dire need of a performance upgrade, although some OEM provide decently flowing intake headers.

Fitting big valve kits, carrying out port work and head flowing will also improve bhp, the fantastic side effect is it will make space for increasing the bhp increase on other tuning mods.

B48 performance cam tips.

Different B48 engines respond better to mild cam durations so view each engine as unique.

The ECU mapping and injectors and fuel pump also have an effect on the bhp gains you'll achieve.

A longer valve duration 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 power band gains are on offer for cam upgrades.

NB: Fast road camshafts usually bump the bhp and torque over the rev range, you could sacrifice a little low down bhp but higher rpm power will be better.

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

On a car used daily you must carefully try to match your bhp range to your usage of the car.

I'd be amazed if you find a B48 Motorsport cam is a pleasure to live with when driving around busy urban areas.

Stage 1, 2 and 3 mods for the B48

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 B48 parts:

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

Stage 2 B48 parts:

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

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

Stage 3 B48 parts:

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

Carefully think through your options and then source your upgrades and set yourself a power target to save yourself from expensive mistakes.

Mapping will help fully realize the full potential of all the parts you've done to your B48.

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 your results will differs on the parts you've carried out and the condition of your engine.

Turbo modifications on the B48

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 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 car is turbo charged tuning mods are going to make more power and you will discover turbocharged engines will have more solid components.

However engines will need better parts at higher power limits

We recommend you find these restrictions and upgrade to higher quality components to cope with the power.

There are many tuners spending a fortune on turbocharger upgrades on the B48 only to suffer the humiliation of seeing the engine literally blow up on it's first outing after it's first rolling road session.

Large upgraded turbos commonly experience a bottom end lag, and low capacity turbos spool up more quickly but don't have the top end torque gains.

Thanks to progress the world of turbos is always developing and we now see variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust flow into two 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 torque gains, although more complex to configure. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the B48

You will need to ensure that the engine is not starved of fuel so need to increase the fuelling when you start exceeding 20% of a performance hike. Don't forget to over specify your flow rate on the injectors.

The accepted safe increase is to add 20% to the flow rate when specifying an injector, this takes into account injector deterioration and gives a bit of spare capacity should the engine require 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 B48 performance exhaust upgrades

You only need to to uprate your exhaust system with an upgraded one is if the existing exhaust is actually causing a restriction.

On most factory exhausts you'll find the exhaust flow rate is still good 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 can help balance the flow of gases through the engine.

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

Usual exhaust restrictions are traced to the catalyst installed, so adding a freer flowing performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the B48

Like most engines an B48, 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 B48, failure to do this will exacerbate engine wear, on a tuned B48 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 B48 why not pop over to the forums at TorqueCars where you can chat about B48 tuning options and read about others projects who may be planning to do similar modifications on their B48.

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