Tuning the BMW N73

"All you need to know about performance parts and tuning the BMW N73 engine!"

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The BMW N73 are fantastic to work on and with the ultimate sports enhancements like ECU maps, turbo kits and camshafts you will substantially enhance your driving pleasure.

The N73 is a NASP V12 and hold the record as the first V12 engine to use gasoline direct port injection DOHC and double Vanos!

Let us review and look at N73 tuning and report on the greatest modifications for your car.

We rely on our visitors to pass on tips and tell us about their projects and what worked on their car, and this article is the culmination of the feedback we have received. First let us look at the history and specs of this engine and then consider which tuning modifications work best on it.

History of the Engine

• N73B60
  327 kW (439 hp)@6,000 rpm 600 nm (443 lbft)@3,950 rpm

• N73B68
  338 kW (453 hp)@5,350 rpm 720 nm (531 lbft)@3,500 rpm

Tuning the BMW N73 and best N73 performance parts.

What are the most effective N73 mods

Just because particular tuning parts are are common on N73 it doesn't mean you should fit it, instead we will optimum tuning parts that will give your N73 the best power gain for you money.

Significant gains on the N73 can be made from cam upgrades. Altering the cam profile alters the intake and exhaust durations on the engine and can dramatically change the torque and power output.

Fast road cams tend to push up the performance throughout the rev band, you could sacrifice a little low end bhp but the high end rpm power will improve.

Motorsport cams, push up 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 daily driver should ideally to optimize your engines power to your cars usage.

I would be surprised if you find a N73 Race cam is a pleasure to live with when driving in heavy traffic.

Some N73 engines respond better to different cam durations so view each engine as unique.

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

A longer valve duration 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.

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Modifying to Stage 1:

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

Modifying to Stage 2:

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

Modifying to Stage 3:

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

Mapping should help to fully realize the full potential of all the modifications you've done to your N73.

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

It is the whole point to any engine tuning job to shove more fuel and air into each cylinder

Intake transmit the air during the suck phase from the intake filter and allow it to be pulled into the engine and mixed with fuel.

Shape and flow characteristics of the Air Intake manifolds can make a substantial effect on to fuel atomisation and engine efficiency on the N73.

I usually find air intake manifolds are ripe for performance upgrades, although a few car makers provide fairly well optimized air intake manifolds.

Larger N73 valves, getting port work and head flowing will also raise power, and significantly will allow you to get a greater power increase on other tuning mods.

Which turbo upgrades are best?

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 N73

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

When your car is turbocharged, parts are going to net you a larger power gain and turbocharged engines already contain many forged and stronger components.

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

It is important to find these limitations and install better quality components to handle the power.

We've seen people spending a loads of money on turbo upgrades on the N73 only to suffer the humiliation of seeing the N73 go up in smoke on it's first outing after it's been finished.

Large capacity turbochargers commonly suffer no power at low rpm, and low capacity turbochargers spool up more quickly but won't have the peak rpm engines power gains.

Thanks to progress the range of turbo chargers is always evolving and we now see variable vane turbo chargers, allowing the vane profile is altered according to speed to lower lag and increase top end bhp and torque.

Twin scroll turbo chargers divert the exhaust gases into a couple of channels and feed these at differently angled vanes in the turbo. They also boost the scavenging effect of the engine.

It is common that there's a limit in the air flow sensor MAF/MAP on these engines when a lot more air is being drawn into the engine.

Going up you'll find 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor was restricting performance at a much lower level.

Adding a supercharger or additional turbo will make large bhp gains, although more difficult to configure. We have this article covering twinchargers if you want to read more.

Fuelling

When you increase the power you will need to look at to the fuelling.

More power needs more fuel. It is important to over specify your injector capacity.

As a rule of thumb add another 20% when specifying an injector, this takes into account injector deterioration and gives some spare capacity should the engine need 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.

Choosing the right performance exhaust

One of the most common mistakes and problems we see in tuning projects is usually down to the exhaust, or rather a poorly chosen exhaust for your engine.

You only need to to boost your exhaust if your current exhaust is actually creating a restriction.

On most factory exhausts you'll find 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.

Don't go with the widest exhaust you can buy you'll reduce the exhaust flow rate - the best for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

Typically exhaust restrictions come around the filters installed, so adding a freer flowing high performance alternative will help avoid this restriction.

Weak spots Issues & problem areas on the N73

The N73 engines are generally reliable and solid as long as they are regularly serviced and maintained.

The Vanos components should be checked, carefully maintained and replaced at high milages.

Regular oil changes are vital on the N73, especially when tuned and will help extend the life and reliability of the engine.

For more information on Tuning your N73 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.

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 tuning mods work best for them on each model of car. Comments are used to improve the accuracy of these N73 articles which are continually updated.

This article was written by Waynne Smith on TorqueCars, and I appreciate your feedback and suggestions. This entry was filed under BMW. You can leave a response below or join TorqueCars forum to discuss this article and car modification in detail with our members.

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