Modding uprating the BMW N45B20S engine!

Everything You Need To Know About "N45B20S Modifications"

How to modify and upgrade the BMW N45B20S

"Comprehensive guide to performance tuning the BMW N45B20S engine!"

Sites like TorqueCars are frequently seeing threads requesting information on how to improve the N45B20S from people wanting to know what are the best tips on N45B20S upgrades. So let us look into BMW N45B20S upgrades and outline the best modifications on this great engine and point out some common pitfalls along the way.

The BMW N45B20S really good project engines and with the right uprated mods like remaps, turbo improvements and camshafts you will improve your driving enjoyment.

Our aim here is to outline options for your N45B20S tuning and provide tips on the best modifications for your car.

Just because particular parts are appear in lots of N45B20S projects it doesn't mean you should fit it, instead we will concentrate on the ultimate parts that will give your N45B20S the best value for money to power increase.

Without us subscribing to the misaprehension of 'if it's shiny and makes more noise it must be good' you seem to get in many tuning magazines and on car forums'.

N45B20S induction kits

Improving air intake on the N45B20S

You need fuel and air for an engine to work. If there is insufficient fuel then it will run lean, if there is not enough air it runs rich sapping power which risks damage to the N45B20S. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So Feeding air and fuel into the N45B20S engine is the whole point to any car tuning job.

It is common that there is a limitation in the air flow sensor AFM/MAP on the N45B20S when a lot more air is being pulled 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.

Headers flow the air during the suck phase from the intake filter and allow it to be drawn into the engine cylinders with fuel for the squish phase.

The shape and flow characteristics of the Intake headers can make a substantial improvement to fuel atomisation on the N45B20S.

Most intake manifold are improved through aftermarket parts, although some car makers provide decently flowing intake manifold.

Larger N45B20S valves, carrying out port matching and head flowing will also boost bhp and torque, and as an added benefit will afford you increasing the bhp and torque increase on other tuning parts.

N45B20S performance cam tips.

Some N45B20S engines respond better to different cam durations than others.

The map and fuel pump and injectors also have an effect on the power gains you'll hit.

Longer 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.

Significant air intake, and exhaust improvements on the N45B20S can be made from cam upgrades. Changing 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 raise the power throughout the rpm band, you could sacrifice a little low down torque but the higher rpm power will be higher.

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

A Motorsport cam will just annoy you whilst in heavy traffic.

You should ideally optimize your torque band to your typical driving style so for a car used daily stick with a shorter duration N45B20S cam

Stage 1, 2 and 3 mods for the N45B20S

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 N45B20S parts:

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

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

Stage 2 N45B20S parts:

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

Stage 3 N45B20S parts:

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

The N45B20S engine blocks respond well to mods and we're finding that there are plenty of modifications and tuning parts out there.

Remapping will help fully realize the full potential of all the tuning parts you've done to your N45B20S.

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 often depend much on the tuning parts you've applied and the condition of your engine.

Turbo modifications on the N45B20S

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 N45B20S.

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 tuning parts are going to make more power and we find turbo charged engines are made with strengthened components.

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

Research these limits and fit higher quality crank and pistons to utilize the power.

We see many guys spending a loads on turbo charger upgrades on the N45B20S only to suffer the indignity of watching the car explode soon after it's been completed.

Large turbo chargers often experience low end lag, and low capacity turbo chargers spool up much more quickly but do not have the top end engines power gains.

In the last 10 years the range of turbochargers is always developing and we are seeing variable vane turbochargers, allowing the vane profile is altered according to speed to lower lag and increase top end bhp.

Twin scroll turbochargers divert the exhaust gases into two channels and push these at differently designed vanes in the turbo charger. 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 bhp and torque gains, although more challenging to configure. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the N45B20S

Don't dismiss the need pay attention to the fuelling when you are increasing the torque - it makes the car more thirsty. It is important to over specify your injectors flow rate.

As a rule of thumb add 20% to the flow rate when buying an injector, helps cope with injector deterioration and provides some 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 N45B20S performance exhaust upgrades

Only look to boost your exhaust system with an upgraded one is if the existing exhaust is actually creating a flow problem.

On most factory exhausts you should find that the flow rate is still fine 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 equal out the flow of air through the engine.

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

Usual exhaust restrictions can be located the emissions filters installed, so adding a faster flowing high 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 N45B20S

Like most engines an N45B20S, 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 N45B20S, failure to do this will exacerbate engine wear, on a tuned N45B20S 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 N45B20S why not pop over to the forums at TorqueCars where you can chat about N45B20S tuning options and read about others projects who may be planning to do similar modifications on their N45B20S.

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