Modifying and Tuning the BMW N55

Modifying and improving: "BMW N55 Tuning"

BMW N55 Tuning Guide

"Comprehensive guide to tuning the BMW N55 engine!"

The BMW N55 are awesome to work on and with carefully chosen modified upgrades like remaps, turbo kits and camshafts you will positively maximise your driving pleasure.

We shall detail the best approach to N55 tuning and summarise the ultimate upgrades.

When talking about the optimum parts for your N55 engine, we are going to focus on the tuning mods that give the best value for money.

Significant gains on the N55 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.

NB: Fast road cams tend to boost the bhp throughout the rev range, you might lose a little low end power but the high end rpm power will be lifted.

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

For a daily driver must carefully try to match your bhp range to your typical driving style.

I'd be surprised if you have ever thought a N55 Competition camshaft is a pleasure to live with when driving in heavy traffic.

Some N55 engines respond better to less aggressive camshaft durations so view each engine as unique.

The map and fuelling also have a large bearing 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.

Our top 7 top upgrades for your motor, and we will break these into stages and discuss them in detail for you.

  1. Map Tunes - remapping, via either OBD port, or piggyback ECU's and aftermarket ECU's can all make decent gains
  2. Fuelling Pump Injectors - You'll need to match the greater air flow with more fuel to unlock the power
  3. Turbo upgrades - Improving the intake charge with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex especially where conversions are required).
  4. Suspension Upgrades - always improve your cars handling, tuning is not just about engine mods
  5. Brake Upgrades - Even before adding power improve your cars brakes to effectively stop the car
  6. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  7. Exhaust - as with intakes it helps to remove a restriction in the exhaust, cats are the usual bottleneck

This video guide to tuning cars is a great starting point to work from in your project.

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

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

Stage 3 mods: Engine balancing & blueprinting, Twin charging conversions, Crank and Piston upgrades to alter compression, Competition cam, Internal engine upgrades (head flowing porting/bigger valves), Adding or Upgrading forced induction (turbo/supercharger).Carefully think through your options and then source your tuning mods and set yourself a power target to save yourself from expensive mistakes.

Mapping will help to establish the full potential of all the upgrades you've done to your N55.

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 outcome often rely on the upgrades you've applied and the condition of your engine.

Pulling more air and fuel into the N55 engine is the whole point to any car tuning job.

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

The intake plenum flow the air during the suck phase from the air cleaner and allow it to be pulled into the engine cylinders.

The shape and flow characteristics of the air Intake manifold can make a noticeable effect on to fuel engine efficiency on the N55.

It's not uncommon that intake manifold are in dire need of aftermarket tuning parts, although some manufacturers provide reasonably good intake manifold.

Adding a N55 larger valve kit, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also raise bhp, the fantastic side effect is it will permit raising the bhp increase on other tuning mods.

N55 Turbo upgrades

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 a separate 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 N55

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes massive power gains.

If your motor has a turbo already fitted parts are relatively easy and turbocharged engines are built with many forged and stronger components.However you will find an engines have limits

Research these limits and fit more solid crank and pistons to utilize the power.

We see many mechanics spending a lots of money on turbo upgrades on the N55 only to suffer the humiliation of seeing the car explode soon after it's finished.

Big capacity turbochargers tend to experience a bottom end lag, and small turbochargers spool up really quickly but don't have the top end torque gains.

Thanks to progress the range of turbos is always developing and we commonly find variable vane turbos, permitting the vane angle is altered according to speed to lower lag and increase top end power.

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

You'll commonly see there is a limit in the air flow sensor AFM/MAF on the N55 when loads more air is being drawn into the engine.

You'll see that 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor sapped bhp at a much lower level.Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large torque gains, although harder to get working. We have this feature on twinchargers if you want to read more.

N55 Fuelling upgrades and mods

You will need to ensure that the engine is not starved of fuel so will need to look at the fuelling when you start going beyond 20% of a power increase.

We strongly recommend you to be generous with 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 affords a bit of 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..

N55 Exhaust upgrades and mods

Only look to boost your exhaust if your current exhaust is creating a restriction in flow.

On most factory exhausts you'll see the 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 increase the flow of air through the engine.

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

Typically exhaust restrictions can be traced to the catalyst installed, so adding a freer flowing sports alternative will help avoid this restriction.

N55 Issues & common problems

The N55 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

Regular oil changes are vital on the N55, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your N55 engine please join us in our friendly forum where you can discuss tuning options in more detail with our N55 owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

Please help us improve these tips by sending us your feedback in the comments box below.

We really like hearing from our readers, and hearing about which parts were the most effective for them, it helps us improve our recommendations and articles to reflect current trends in modifications and ensures that our N55 guides and tips are kept up to date.

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