BMW N46 Tuning

"All you need to know about performance tuning the BMW N46 engine!"

In this article we consider N46 tuning and provide tips on the best modifications for your car. BMW N46 make a good tuning project and with a few sensible modifications like remaps, turbo kits and camshafts you will definitely enhance your driving opportunities.

History, Power & Specs of the Engine

  • N46B18 129 lbft at 3,750 rpm
    2004-2005 E46 316i/316ti
  • N46B20U1 133 lbft at 3,250 rpm
    2005-2007 E87 118i
  • N46B20U2 133 lbft at 3,250 rpm
    2007-2011 E81/E87 118i
    2007-2013 E90 318i
  • N46B20O0  A 148 lbft at 3,750 rpm
    2004-2006 E46 318i, 318Ci and 318ti
  • N46B20O1  148 lbft at 3,600 rpm
    2004-2007 E83 X3 2.0i
    2005-2008 E85 Z4 2.0i
    2004-2007 E87 120i
    2005-2007 E90/E91 320i
  • N46NB20  148 lbft at 3,000 rpm
    2007-2011 E81/E82/E87/E88 120i
    2007-2013 E90/E91/E92/E93 320i
    2007-2010 E60 520i
    2009-2015 E84 X1 sDrive18i / xDrive18i
    2007-2010 E83 X3 2.0i

Tuning the BMW N46 and best N46 performance parts.

Best N46 parts

The best N46 upgrades on an engine are as we have found the ones that give the best value for money.

We won't be swayed by popular N46 upgrades, they need to be cost effective.

Significant gains on the N46 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

Fast road camshafts usually boost the torque through the rpm band, you may lose a little bottom end torque but high end rpm power will be better.

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

On a car driven daily you need to match your engines power to your cars usage.

I'd be surprised if you have ever thought or claimed that a N46 Competition camshaft is a pleasure to live with when in heavy traffic because low end power will be very lumpy. Competition cams are designed for maximum power at the top end of the RPM range, a place that most daily commutes will not permit!

Some N46 engines respond better to less aggressive camshaft durations than others.

The engine timing and injectors and fuel pump also will say much on the bhp gains you'll make.

Altering valve durations can alter the bhp 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.

Typical stage 1 mods often include: Intake headers, Fast road camshaft, Sports exhaust manifold, drilled & smoothed airbox, Remaps/piggy back ECU, Panel air filters.

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

Typical stage 3 mods often include: Internal engine upgrades (head flowing porting/bigger valves), Crank and Piston upgrades to alter compression, Twin charging conversions, Competition cam, Engine balancing & blueprinting, Adding or Upgrading forced induction (turbo/supercharger).

The N46 engines make great tuning projects and we're pleased to see that there are increasing numbers of parts and tuning parts about.

remap allows a tuner to establish the full potential of all the parts you've fitted to your N46.

(In some cases, as the factory ECU is locked flashing is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but make sure it has knock protection and that you get it setup properly.)

It will usually give you around 30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but the outcome will rely on the parts you've fitted and the condition of your engine.

Feeding air into each cylinder is the aim to any engine upgrade job.

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

The bore size, shape and flow rate of the Intake headers can make a large effect on to fuel delivery on the N46.

On popular production engines headers are needing motorsport parts, although some OEM provide fairly well optimized headers.

Fitting big valve kits, getting port matching and head flowing will also boost bhp and torque, the fantastic side effect is it will afford you a better bhp and torque increase on other upgrades.

N46 Turbo upgrades

NASP engines need quite a lot of work when you add a turbo, so we have a separate guide to help you take into account the pros and cons of going this route on your N46

There are some kits around, and typically running around 0.6 bar of boost will give you another 70hp, beware of the manifolds though, left hand drive cars need a different design.

You will need a custom exhaust manifold, oil feed and return kit. We would recommend a Wlabro 255l/h fuel pump and a fuel pressure regulator and boost, temp,oil pressure, oil temp and air/fuel gauges so you can monitor what is going on, it can prevent problems and help you diagnose faults and issues with your installation.

A manual boost controller is also a good option, we would recommend a set and forget installation for ease and simplicity.

Don't forget the intercooler and we would recommend a front mounted intercooler on the N46, but you might need to modify your cars front to get this to fit.

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.

When the engine has a turbocharger upgrades are relatively easy and turbo charged engines already contain harder and stronger components.

However every engines will have power limits

Research these limitations and fit forged components to cope with the power.

There are many mechanics spending a loads of money on turbo charger upgrades on the N46 only to have the engine block explode on it's first outing after it's been completed because they didn't map it correctly or set the boost too high.

Large turbochargers commonly experience no power at low rpm, and smaller turbochargers spool up much more quickly but do not have the peak rpm engines power gains.

We are pleased that the selection of turbochargers is always evolving and we commonly find variable vane turbochargers, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbochargers divert the exhaust gases into a couple of channels and push these at differently angled vanes in the turbocharger. They also improve the scavenging effect of the engine.

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

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

Adding a supercharger or additional turbo will make large power gains, although harder to install. We have this article on twincharging if you want to read more.

N46 Fuelling

You will need to ensure that the engine is not starved of fuel so will have to uprate the fuelling when you start extending past 20% of a bhp increase.

A fuel pump will also be needed for more extreme tuning projects, it's not just the injectors or fuel pressure regulator that does all the work, it needs to get a supply of the fuel.

Don't forget to over specify your flow rate on the injectors.

The rule of thumb is to add another 20% when fitting an injector, helps cope with injector deterioration and gives a bit of spare capacity should the engine require more fuel.

We think this one is common sense, but you'll need to match your fuel injector to the type of fuel your car uses as well.

Exhaust upgrades for the N46

You may need to replace your exhaust if your current exhaust is actually creating a restriction.

Exhausts DO NOT ADD POWER, they remove a restriction, so if there is not a restriction you won't be gaining anything.

On most factory exhausts you'll find the flow rate is still 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 generally help improve air flow out of the engine but avoid an exhaust that is too wide or you might just stuff your flow rate and make things worse. So generally speaking, keep to a size of 1.5 to 2.5 inches for best results.

Common exhaust restrictions are traced to the catalyst and filters installed, so adding a faster flowing race alternative such as a sports catalyst pretty much removes this restriction, thanks to it's larger size and surface area, and will effectively raise the performance to levels you would expect without having a catalyst installed, but keeps the car road legal.

Weak spots Issues & problem areas on the N46

The N46 engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

Regular oil changes are vital on the N46, especially when tuned and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice on Tuning your N46 engine please join us in our friendly forum where you can discuss tuning options in more detail with our tuning articles to get a full grasp of the benefits and drawbacks of each modification.

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4 Responses to “N46 Tuning”

  1. Shaun says:

    Hi… I have been looking for info line for a really long time.Thanx somuch this on point advice with pros & cons will help allot. Keep ot up

  2. Dave says:

    Hi there

    I’m from the UK and I have a BMW 318i M Sport which also has the N46 engine. I was wondering where I would be able to purchase a turbo kit and where I’d be able to get all these upgrades. I’ve done tonnes of research but I just can’t find the right places.

  3. Jake Coley says:

    Hi, been looking to turbo my n46 e91 320i
    Is there any kits that I would buy?

    • TorqueCars says:

      It depends where you live, Laurent motors in France were listing a kit for these engines. We’d love to hear your experiences with this project so please join us in the forums and keep us posted.

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