Modding upgrading and tuning the BMW S55 engine!

Car tuning tips:S55 Modifications"

S55 Modifications Guide

How to modify and upgrade the BMW S55

"Comprehensive guide to tuning the BMW S55 engine!"

Sites like TorqueCars are always getting posts about how to improve the S55 from people inquiring about getting more power from the S55 and wanting to know what are the premier S55 mods that work. So let us look into BMW S55 upgrades and outline the best upgrades on this great engine and point out some problems along the way.

Now we shall examine the options for your S55 tuning and outline the best modifications. BMW S55 make a good tuning project and with the best performance mods like remaps, turbo improvements and camshafts you will maximise your driving pleasure.

When talking about the best parts for your S55 engine, we are going to concentrate on the upgrades that give the best power gain for you spend.

S55 induction kits

Improving air intake on the S55

You need air and fuel for an engine to work. If there is too little fuel then it will run lean, if there is a lack of air it runs rich sapping power which risks damage to the S55. 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 performance tuning project to push fuel and air into the S55 engine but this has a knock on effect with the air flow sensor.

It is not unusual that there is a restriction in the air flow sensor MAP/MAF/AFM on the S55 when considerably more air is being sucked into the engine.

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

Headers carry the air during the suck phase from the intake filter and allow it to be drawn into the engine and mixed with fuel.

The size of bore and shape and flow characteristics of the Air Intake manifolds can make a big change to fuel mixing and power on the S55.

Many mass produced engine plenum chambers are in desperate need of aftermarket parts, although some manufacturers provide reasonably well designed plenum chambers.

Big valve conversions on the S55, doing some port matching and head flowing will also improve performance, and importantly will make space for raising the performance increase on other modifications.

S55 performance cam tips.

Each engine responds better to more aggressive cam durations than others.

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

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.

Altering your S55 cam will make a dramatic difference to the engine bhp. Choosing a higher performance cam profile raises the bhp accordingly.

NB: Fast road cams usually bump the torque throughout the rev band, you may lose a little low down torque but the higher rpm power will improve.

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

A Motorsport and race camshaft will just annoy you whilst driving in heavy traffic.

You should ideally match your bhp range to your typical driving style so for a car driven daily stick with a shorter duration S55 camshaft

Stage 1, 2 and 3 mods for the S55

Stage 1 S55 parts:

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

Stage 2 S55 parts:

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

Stage 3 S55 parts:

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

Plan your options and then source your parts and set yourself a power target to avoid expensive mistakes.

Mapping helps to establish the full potential of all the tuning mods you've done to your S55.

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

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 figures achieved may depend much on the tuning mods you've carried out and the condition of your engine.

Turbo modifications on the S55

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 S55.

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 a car has a turbocharger upgrades are giving better power gains and turbo engines already contain strengthened components.

There are weak spots for every engine, with some being over specified and some only just able to handle stock power

It is important to find these limitations and fit better pistons and crank to handle the power.

We see many car owners spending a loads on turbo upgrades on the S55 only to suffer the indignity of watching the whole thing go up in smoke on it's first outing after it's first rolling road session.

Large capacity turbo chargers commonly experience a bottom end lag, and small turbo chargers spool up much more quickly but won't have the high rpm power band gains.

In recent times the selection of turbo units is always evolving and we now see variable vane turbo units, allowing the vane profile is altered according to speed to lower lag and increase top end performance.

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

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large bhp gains, although more difficult to setup. We have this article on twincharging if you want to read more.

Tips about fuel supply on the S55

When you raise the bhp you will need to pay attention to to the fuelling.

More bhp needs more fuel. It is important to be generous with your injectors flow rate.

As a rule of thumb add 15% capacity 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 S55 performance exhaust upgrades

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

On most factory exhausts you should find that your 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 usually air flow from the engine but avoid an exhaust that is too big or you could will reduce the flow rate. Stick to one and a half to two and half inches for best results.

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

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

Faults issues and things to look out for on the S55

Like most engines an S55, 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 S55, failure to do this will exacerbate engine wear, on a tuned S55 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 S55 why not pop over to the forums at TorqueCars where you can chat about S55 tuning options and read about others projects who may be planning to do similar modifications on their S55.

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