Modding upgrading and tuning the BMW B38 engine!

Tuners tips on "B38 Modifications"

B38 Modifications Guide

How to modify and upgrade the BMW B38

"Comprehensive guide to performance tuning the BMW B38 engine!"

Popular tuning sites like TorqueCars often are getting emails about how to improve the B38 from people wanting to know what are the best tips on B38 power upgrades. So let us look into BMW B38 upgrades and outline the best modifications on this great engine and point out some potential pitfalls along the way.

The BMW B38 are popular tuning projects and with carefully chosen sports parts like a remap, turbo upgrades and camshafts you will greatly improve your driving fun.

Let us consider B38 tuning and report on the premier mods that work.

When talking about the best parts for your B38 engine, we are going to concentrate on the mods that give the best power gain for you spend.

B38 induction kits

Improving air intake on the B38

You need air matched to fuel for an engine to work. If there is not enough fuel then it will run lean, if there is little flow of 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 it's important to any car tuning job to pull more air and fuel into the B38 engine but this has a knock on effect with the air flow sensor.

It is common that there's a limitation in the air flow sensor (AFM/MAF/MAP) on the B38 when considerably more air is being fed into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp and torque at a much lower level.

Intake headers carry the during the engines suck phase from the air filter and allow it to be pulled into the engine cylinders with fuel for the squish phase.

The size of bore and shape and flow rate of the Plenum can make a noticeable difference to to fuel engine efficiency on the B38.

I usually find air intake manifolds are crying out for an upgrade, although a few makers provide reasonably well designed air intake manifolds.

Increasing the B38 valve size, carrying out port work and head flowing will also boost power, and importantly will afford you an improved power increase on other parts.

B38 performance cam tips.

Some B38 engines respond better to mild camshaft durations so view each engine as unique.

The ECU mapping and injectors and fuel pump also have an effect 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.

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 torque gains are on offer for cam upgrades.

NB: Fast road camshafts usually bump the performance through the rpm band, you may lose a little bottom end bhp but the top end will be higher.

Motorsport and race camshafts, 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 optimize your power band to your usage of the car so for a road car stick with a fast road B38 camshaft

Stage 1, 2 and 3 mods for the B38

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 B38 parts:

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

Stage 2 B38 parts:

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

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

Stage 3 B38 parts:

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

The B38 units make great tuning projects and thanks to their popularity there is an increase of upgrades and tuning parts about.

Mapping allows a tuner to to establish the full potential of all the parts you've done to your B38.

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 the end result may differs on the parts you've done and the condition of your engine.

Turbo modifications on the B38

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 B38.

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 the engine has a turbocharger upgrades are going to make more power and turbo charged engines will have many forged and stronger components.

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

We recommend you find these restrictions and upgrade to better quality crank and pistons to utilize the power.

We see many people spending a a stack of money on turbo charger upgrades on the B38 only to see the engine block catastrophically fail just after it's completed.

Large turbo chargers will usually suffer a bottom end lag, and low capacity turbo chargers spool up much more quickly but don't have the peak end bhp gains.

In recent times the selection of turbos is always improving and we now see variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end power.

Twin scroll turbos divert the exhaust gases into a couple of channels and push these at differently angled vanes in the turbo. They also increase 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 setup. We have this guide to twinchargers if you want to read more.

Tips about fuel supply on the B38

You will need to ensure that the engine is not starved of fuel so will need to pay attention to the fuelling when you start going beyond 20% of a torque hike. Most tuners we speak with say to be generous with your flow rate on the injectors.

The rule of thumb is to add 20% when fitting an injector, this allows for injector deterioration and allows you some spare capacity should the engine need 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 B38 performance exhaust upgrades

Only look to improve your exhaust system with an upgraded one is if your current exhaust is actually creating a restriction.

On most factory exhausts you should find that your flow rate is still ok 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 the exhaust is too big, ie: it's over two and a half inches diameter, you will lose a lot of your flow rate and end up losing power and torque.

The usual suspects causing problems in your exhaust flow rate come around the emissions filters installed, so adding a better flowing performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the B38

Like most engines an B38, 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 B38, failure to do this will exacerbate engine wear, on a tuned B38 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 B38 why not pop over to the forums at TorqueCars where you can chat about B38 tuning options and read about others projects who may be planning to do similar modifications on their B38.

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