Modding tuning and best performance upgrades on the BMW N73B68 engine!

Explore N73B68 Modifications"

How to modify and upgrade the BMW N73B68

"Comprehensive guide to performance parts and tuning the BMW N73B68 engine!"

Forums like the one at TorqueCars often are getting posts about how to improve the N73B68 from people wanting to know what are the ultimate N73B68 mods that work. So let us look into BMW N73B68 modifications and outline the best mods that work on this great engine and point out some problems along the way.

The BMW N73B68 make awesome project engines and with carefully chosen uprated parts like remapping, turbo kits and camshafts you will dramatically increase your driving pleasure.

We shall review N73B68 tuning and provide tips on the best upgrades.

Just because particular modifications are appear in lots of N73B68 projects it doesn't mean you should fit it, we will concentrate on the best modifications that will give your N73B68 the biggest power gain return for your cash.

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'.

N73B68 induction kits

Improving air intake on the N73B68

You need air matched to fuel for an engine to work. If there is a lack of fuel then it will run lean, if there is insufficient air it runs rich resulting in lost power which risks damage to the N73B68. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So the fundamental goal to any tuning project to feed more air and fuel into each cylinder but this has a knock on effect with the air flow sensor.

You'll commonly see there's a restriction in the air flow sensor MAF/MAP on the N73B68 when considerably more air is being pulled into the engine.

We note 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited torque at a much lower level.

The intake plenum take the on the suck phase from the air filter and allow it to be drawn into the engine cylinders.

Structure and rate of flow of the Headers can make a big effect on to fuel atomisation and engine efficiency on the N73B68.

On popular production engines intake manifold are ripe for motorsport parts, although a few makers provide decently flowing intake manifold.

Big valve conversions on the N73B68, getting port work and head flowing will also boost bhp, the fantastic side effect is it will permit an improved bhp increase on other mods.

N73B68 performance cam tips.

Each engine responds better to mild cam durations so set your engine up on a rolling road.

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

A longer valve duration 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.

The camshaft profile plays a big part in the engines power output so camshaft upgrades make quite a large difference. The intake & exhaust durations will alter depending on the chosen camshaft profile, so large bhp gains are on offer for camshaft upgrades.

NB: Fast road cams tend to increase the performance throughout the rev range, you could drop a little low end bhp but high end rpm power will be lifted.

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

A Competition camshaft is not great in heavy traffic.

You should ideally optimize your torque band to your cars usage so for a car driven daily stick with a fast road N73B68 camshaft

Stage 1, 2 and 3 mods for the N73B68

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 N73B68 parts:

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

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

Stage 2 N73B68 parts:

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

Stage 3 N73B68 parts:

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

Carefully think through your options and then source your tuning mods and set yourself a power target to avoid expensive mistakes.

Remapping helps to establish the full potential of all the tuning parts you've done to your N73B68.

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

Turbo modifications on the N73B68

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 N73B68.

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

If your car is turbocharged, modifications are simpler to install and we find turbo engines are made using uprated components.

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

Discover these restrictions and fit higher quality crank and pistons to survive the power.

There are many people spending a a stack of money on turbo upgrades on the N73B68 only to suffer the indignity of watching the engine literally blow up on it's first outing after it's first rolling road session.

Big turbos tend to experience low end lag, and low capacity turbos spool up really quickly but do not have the top end torque gains.

Thanks to progress the market of turbos is always developing and we commonly find variable vane turbos, where the vane profile is altered according to speed to lower lag and increase top end torque.

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

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

Tips about fuel supply on the N73B68

You will need to ensure that the engine is not starved of fuel so must ramp up the fuelling when you start extending past 20% of a bhp and torque hike. Most tuners we speak with say to over specify your injector capacity.

As a rule of thumb add another 20% when specifying an injector, this accounts for injector deterioration and allows a bit of 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 N73B68 performance exhaust upgrades

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

On most factory exhausts you'll find your flow rate is ok 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.

Please dont run with the largest exhaust you can source this will reduce the exhaust flow rate - the best exhausts 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.

Typically exhaust restrictions can be located the catalyst installed, so adding a higher flowing 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 N73B68

Like most engines an N73B68, 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 N73B68, failure to do this will exacerbate engine wear, on a tuned N73B68 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 N73B68 why not pop over to the forums at TorqueCars where you can chat about N73B68 tuning options and read about others projects who may be planning to do similar modifications on their N73B68.

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