Modding upgrading and tuning the BMW N42 engine!

All you need to know about "N42 Modifications"

N42 Modifications Guide

How to modify and upgrade the BMW N42

"Comprehensive guide to tuning the BMW N42 engine!"

TorqueCars often are getting messages asking how to improve the N42 from people wanting to know what are the best tips for N42 mods that work. So let us look into BMW N42 tuning mods and outline the best modifications on this great engine and point out some potential pitfalls along the way.

The BMW N42 make awesome project engines and with carefully chosen parts like remaps, turbo upgrades and camshafts you will substantially maximise your driving pleasure.

Car Tuning Tips will examine the options for your N42 tuning and summarise the premier modifications for your car.

Just because particular mods are appear in lots of N42 projects it doesn't mean it is good, we will focus on the best mods that will give your N42 the best power gain for you money.

Without us subscribing to the popular mentality 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'.

N42 induction kits

Improving air intake on the N42

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

So the aim to any engine performance tuning project to pull more air and fuel into your N42 but this has a knock on effect with the air flow sensor.

It is common that there's a restriction in the air flow sensor AFM/MAF on the N42 when a lot 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 was restricting bhp and torque at a much lower level.

Intake manifolds transmit the on the suck phase from the filter and allow it to be drawn into the engine and mixed with fuel.

Shape and flow rate of the Plenum can make a large improvement to fuel mixing and power on the N42.

Commonly we find the intake headers are needing motorsport parts, although a few car makers provide well optimised intake headers.

Fitting big valve kits, doing a bit of 3 or 5 angle valve jobs and porting and head flowing will also improve bhp, the fantastic side effect is it will afford you raising the bhp increase on other upgrades.

N42 performance cam tips.

Different N42 engines respond better to extreme cam durations so set your engine up on a rolling road.

The map and fuel pump and injectors also will say much on the torque gains you'll make.

A longer valve duration 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.

Altering your N42 cam will make a dramatic difference to the engine torque. Choosing a higher performance cam profile raises the torque accordingly.

NB: Fast road camshafts tend to increase the torque across the rpm band, you may sacrifice a little low down bhp but higher rpm power will improve.

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

For a road car you must carefully try to match your torque band to your driving style.

I'd be shocked if you find a N42 Competition camshaft is a pleasure to live with when driving in heavy traffic.

Stage 1, 2 and 3 mods for the N42

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 N42 parts:

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

Stage 2 N42 parts:

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

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

Stage 3 N42 parts:

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

The N42 engines respond well to mods and we're pleased to see that there is an increase of modifications and performance parts out there.

ECU flashing allows a tuner to fully realize the full potential of all the parts you've done to your N42.

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 power output may depend much on the parts you've fitted and the condition of your engine.

Turbo modifications on the N42

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 N42.

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 a car is fitted with a turbo tuning parts are giving better power gains and you will discover turbo engines already contain stronger components.

However you will find an engines will need better parts at higher power limits

Discover these restrictions and fit higher quality components to utilize the power.

It's not unheard of drivers spending a fortune on turbocharger upgrades on the N42 only to watch the car go up in smoke on it's first outing after it's finished.

Bigger turbos tend to suffer low end lag, and small turbos spool up really quickly but do not have the peak end engines power gains.

Thanks to progress the range of turbos is always increasing and we are seeing variable vane turbos, allowing the vane profile is altered according to speed to lower lag and increase top end performance.

Twin scroll turbos divert the exhaust flow into a couple of channels and feed these at differently profiled vanes in the turbocharger. They also improve the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large power gains, although more complex to configure. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the N42

Don't overlook the need to boost the fuel delivery when you are increasing the bhp and torque - it makes the car more thirsty. We would recommend you to over specify your flow rate on the injectors.

As a rule of thumb add 15% to the flow rate when buying an injector, which takes into account injector deterioration and allows a little 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 N42 performance exhaust upgrades

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

On most factory exhausts you'll see the exhaust flow rate is 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.

Note that with the largest exhaust you can buy this will slow up the exhaust flow rate - the best for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

Usual exhaust restrictions can be traced to the catalysts installed, so adding a higher flowing high performance alternative will help avoid this restriction.

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

Faults issues and things to look out for on the N42

Like most engines an N42, 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 N42, failure to do this will exacerbate engine wear, on a tuned N42 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 N42 why not pop over to the forums at TorqueCars where you can chat about N42 tuning options and read about others projects who may be planning to do similar modifications on their N42.

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