BMW N43 Tuning

"All you need to know about performance tuning the BMW N43 engine!"

One engine that keeps cropping up in emails and questions we get sent, is the N43, and what parts work best on it. So this guide has been assembled which covers our go to modifications that you should tune and outline which modifications we feel are the best.

Now we shall outline options for your N43 tuning and summarise the ultimate mods that work. BMW N43 have loads of potential and with carefully picked tuning mods like ECU maps, turbo upgrades and camshafts you will really maximize your driving enjoyment.

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History of the N43 Engine

N43B16  1,599 cc  -121 bhp 118 lbft

The N43 replaced the BMW N45 engine and, similar to the N45, does not have Valvetronic.

It was fitted to the following cars

N43B20 1,995 cc - 168 bhp (155 lbft)

In 2009, the 1,995 cc (121.7 cu in) N43B20 replaced theN43B16 in the 116i. Power remained at 90 kW (121 bhp), however torque was increased.

It was fitted to the following cars

There were a few power version differences of the N43 a 121 bhp 141 bhp and 168bhp versions.

Tuning the BMW N43 and best N43 performance parts.

Best N43 upgrades

Just because particular tuning mods are common on the N43 it doesn't mean you should fit it, so we'll focus on the best tuning mods that will give your N43 the best value for money to power increase.

N43 Camshaft Upgrades

Getting a fast road cam will work better at top end power so are more suited to petrol engines, than diesel ones. In most cases you will see top end power increases through performance camshafts on most engines.

Significant gains on the N43 can be made from camshaft upgrades. Altering the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

Fast road camshafts tend to bump the torque across the rev range, you may sacrifice a little low-end power but high end rpm power will be better.

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

In a car driven daily one must carefully try to optimize your engine's power to your usage of the car.

I would be surprised if you have found a N43 Race camshaft is a delight when on the daily commute.

The low end idle will typically be lumpy and irregular, and this is something you'd notice on a track when you drive in the upper third of the rpm band, but on roads this is a serious issue and we've heard from lots of drivers regretting their decision to install a more extreme competition cam profile to their engine.

Some N43 engines respond differently primarily due to the airflow when cams are fitted depending on the cam being more or less aggressive cam durations than others as unique due to manufacturing tolerances and quality variations so set your engine up on a rolling road.

The map and fuelling also will say much on the bhp gains you'll hit.

Extending exhaust or intake durations can alter the bhp range, and on most engines there are some advantages to extending the intake or exhaust durations and valve lift.

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Best mods for your N43

  1. Fast road cams are one of the most significant mechanical changes, but they must be setup by someone who knows what they are doing and they are not always easy to source but you might find a local firm to regrind a stock camshaft .
  2. Tunes - A tune/remap offers the most advantage compared to your outlay, aftermarket ECUs, and inline Tuning boxes are all alternatives.
  3. Forced induction upgrades - forced induction is the most efficient approach to increase air supply, ensuring you are able to use more fuel and make power gains. It is one of the most complex upgrades but provides the best gains.
  4. Internal engine mods - crank, pistons, conrods & compression ratio including balancing and blueprinting
  5. Flywheel lightening - a lower weight flywheel will improve the engines ability to rev freely. But not always suitable for all N43 engines.
  6. Intake Mods and Performance Exhausts - NB: on their own these mods won't ADD POWER , but they can help enhance power after other mods by removing the restriction.

N43 Tuning Stages

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

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

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

The N43 engine blocks make great tuning projects and we're finding that there is an increase of parts and tuning parts about.

ECU Mapping Improvements for the N43

ECU mapping should help to release the full potential of all the tuning mods you've done to your N43.

(Sometimes flashing the ECU is not an option, so an aftermarket ECU is the route to take, and many of these will outperform factory ECU's but check it has knock protection and that you get it correctly setup.) It will usually give around 30% more power on turbocharged vehicles and you can expect to see around 15% on NA (naturally aspirated) engines, but your results may rely on the tuning mods you've applied and the condition of your engine.

Air Flow improvements on the N43

Pushing air into the N43 engine is the main goal to any engine tuning project.

Intake flows the air from the intake filter and allow it to be pulled into the engine cylinders.

Shape and flow characteristics of the Intake manifolds can make a large change to fuel atomization and engine efficiency on the N43.

It's not uncommon that plenum chambers are in desperate need of an upgrade, although a few OEM provide well optimised plenum chambers.

Fitting big valve kits, doing some port matching and head flowing will also increase torque, this will make space for a better torque increase on other parts.

N43 Turbo upgrades

NA (naturally aspirated) 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 N43

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.

There are weak spots for every engine, with some being very over-engineered and some just sufficiently able to handle stock power. We recommend you find these limitations and fit forged components to utilize the power.

It's not unheard of people spending a lot of money on turbocharger upgrades on the N43 only to suffer the indignity of watching the engine literally blow up on it's first outing after it's used in anger.

Bigger capacity turbo units often experience low end lag, and small turbo units spool up more quickly but won't have the peak end bhp gains.

Over the last 20 years the choice of turbos is always evolving and we commonly find variable vane turbos, permitting the vane profile is altered according to speed to lower lag and increase top end performance.

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

It is common that there is a limit in the air flow sensor MAF/MAP on the N43 when a lot 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 limited bhp at a much lower level.

Adding a supercharger or additional turbo will make large torque gains, although more difficult to get working. We have this feature on twinchargers if you want to read more.

N43 Fuelling Upgrades

Don't omit to look at the fuel delivery when you are increasing the bhp - it makes the car more thirsty. Boosting the fuel pressure provides a more snappy the acceleration responsiveness.We strongly recommend you to over specify your injector capacity.

The accepted safe increase is to add another 20% when specifying an injector, helps cope with injector deterioration and affords 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.

N43 Performance Exhausts

Only look to increase your exhaust if your exhaust is creating a restriction.

On most factory exhausts you'll see the flow rate is fine 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 will certainly help air flow out of the engine but avoid an exhaust that is too big or you may end up reducing the flow rate. Keep the exhaust pipes to around 2 to 2.5 inches for best results.

For road going cars mods such as a sports catalyst pretty much remove this restriction, thanks to its 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. And will allow the full exhaust flow due to its higher internal surface area and design.

The alternative test pipe mod or catalyst removal should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars (and in some you can't even replace a working catalyst).

Weak spots, Issues & problem areas on the N43

The N43 engines are not bad as far as reliability goes as long as they are well maintained.

Carbon build up in the head, particularly around the valves which will reduce power and smooth running, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on intake cleaning guide Avoid short journeys and use good quality fuel.

Service time oil changes are essential on the N43, and more importantly so when the car is tuned and will help ensure the reliability of the engine.

If you want to learn more, or just get some friendly advice on Tuning your N43 engine please join us in our friendly forum where you can discuss N43 tuning options in more detail with our N43 owners. It would also be worth reading our unbiased BMW tuning articles to get insights into each modification and how effective they will be.

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

We love to hear what our visitors have got up to and which mods work best for them on each model of car. We use your comments and feedback to improve the accuracy of these N43 tuning guides which get regular updates and revisions.

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