Tuning the BMW N73B60 / N73B68

"Comprehensive guide to tuning and performance parts on the BMW N73B60 / N73B68 engine!"

The BMW N73B60 / N73B68 great bases for a tuning project and with the right modified parts like remapping, turbo improvements and camshafts you will positively maximise your driving opportunities.

Let us outline options for your N73B60 / N73B68 tuning and point out the optimum modifications for your car.

When talking about the best best for your N73B60 / N73B68 engine, we are going to concentrate on the tuning parts that give the best power gain for you spend.

Altering your N73B60 / N73B68 cam will make a dramatic difference to the engine engines power. Choosing a higher performance cam profile raises the engines power accordingly.

NB: Fast road cams usually push up the power across the rev band, you could drop a little low end power but top end will improve.

Race cams, push up the top end band but as a result the car will not idle smoothly and low end power nearly always suffers.

A Motorsport camshaft will just annoy you whilst driving in heavy traffic.

You should ideally optimize your torque band to your typical driving style so for a car driven daily stick with a fast road N73B60 / N73B68 camshaft

Some N73B60 / N73B68 engines respond better to different camshaft durations so view each engine as unique.

The ECU mapping and injectors and fuel pump also will say much on the power gains you'll achieve.

Extending exhaust or intake durations 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.

Stage 1 modifications: Panel air filters, Fast road camshaft, Intake headers, Sports exhaust manifold, Drilled & smoothed airbox, Remaps/piggy back ECU.

Stage 2 modifications: fuel pump upgrades, Ported and polished head, Sports catalyst & performance exhaust, Fast road cam, induction kit, high flow fuel injectors.

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

The N73B60 / N73B68 units are fantastic to work on and we're happy to report there are increasing numbers of modifications and tuning parts around.

Remaps allows a tuner to to establish the full potential of all the mods you've fitted to your N73B60 / N73B68.

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

Feeding air and fuel into each cylinder is the whole point to any engine upgrade job.

Intake manifold transmit the air from the air cleaner and allow it to be fed into the engine cylinders with fuel for the squish phase.

Design and flow rate of the Plenum can make a large change to fuel delivery on the N73B60 / N73B68.

Most intake headers are crying out for aftermarket parts, although a few makers provide well optimised intake headers.

Increasing the N73B60 / N73B68 valve size, doing a bit of N73B60 / N73B68 port enlargement and head flowing will also increase power, and as an added benefit will give you a better power increase on other modifications.

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 N73B60 / 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 superb power gains.

When a car is fitted with a turbo upgrades are more reliable and you'll see that turbo charged engines are made using harder and stronger components.

However most engines will have power limits

Research these limitations and upgrade to better pistons and crank to utilize the power.

We see many mechanics spending a loads on turbo charger upgrades on the N73B60 / N73B68 only to see the motor go up in smoke just after it's used in anger.

Large turbo units will usually experience no power at low rpm, and low capacity turbo units spool up more quickly but do not have the peak rpm power band gains.

Over the last 20 years the selection of turbochargers is always developing and we are seeing variable vane turbochargers, permitting the vane angle is altered according to speed to lower lag and increase top end performance.

Twin scroll turbochargers divert the exhaust flow into two channels and feed these at differently profiled vanes in the turbo. They also increase the scavenging effect of the engine.

It is not unusual that there's a restriction in the air flow sensor AFM/MAF on the N73B60 / N73B68 when loads more air is being fed into the engine.

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

Adding a supercharger or additional turbo will make large bhp gains, although more complex to install. We have this feature on twinchargers if you want to read more.

Fuelling upgrades and mods

When you improve the performance you will need to increase to the fuel delivery.

More performance needs more fuel. Don't forget to be generous with your injector capacity.

The rule of thumb is to add 20% to the flow rate when specifying an injector, helps cope with injector deterioration and allows 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 and mods

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

On most factory exhausts you'll find your 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 generally help improve air flow from the engine but do not go too large or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches for best results.

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

Weak spots, Issues & common problem areas on the N73B60 / N73B68

The N73 engines, if regularly serviced and maintained, are generally very reliable and have few issues.

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

Regular oil changes are vital on the N73, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

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.

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.

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