Tuning the BMW M52

"Comprehensive guide to performance parts and tuning the BMW M52 engine!"

The BMW M52 great bases for a tuning project and with the best tuning mods like remapping, turbo improvements and camshafts you will certainly increase your driving pleasure.

This pages aim is consider M52 tuning and summarise the optimum modifications.

When talking about the best best for your M52 engine, we are going to concentrate on the modifications that give the best value for money.

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

NB: Fast road cams normally push up the performance through the rev range, you may lose a little low end torque but your high end rpm power will be better.

Competition 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.

For a road car you need to optimize your bhp range to your driving style.

I would be surprised if you have found a M52 Motorsport and race camshaft is a pleasure to live with when driving in heavy traffic.

Different M52 engines respond better to more or less aggressive cam durations so set your engine up on a rolling road.

The map and injectors and fuel pump also will say much on the torque gains you'll achieve.

A longer valve duration can alter the torque 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: Drilled & smoothed airbox, Intake headers, Fast road camshaft, Panel air filters, Remaps/piggy back ECU, Sports exhaust manifold.

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

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

The M52 power plant are fantastic to work on and we're happy to report there are increasing numbers of upgrades and tuning parts out there.

ECU flashing should help to to establish the full potential of all the upgrades you've fitted to your M52.

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

Forcing air and fuel into your M52 is the aim to any engine tuning task.

Intake headers carry the air from the air cleaner and allow it to be drawn into the engine cylinders with fuel for the squish phase.

Structure and flow rate of the Intake headers can make a noticeable improvement to fuel atomisation on the M52.

Many mass produced engine intake headers are in desperate need of aftermarket tuning parts, although some car makers provide reasonably well designed intake headers.

Fitting big valve kits, doing a bit of port matching and head flowing will also improve bhp, & more importantly will give you raising the bhp increase on other parts.

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 M52

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.

When your motor has a turbocharger tuning parts are giving better power gains and most turbocharged engines are made using many forged and stronger components.

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

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

It's not unheard of people spending a fortune on turbo upgrades on the M52 only to watch the M52 literally blow up just after it's been enthusiastically driven.

Bigger capacity turbochargers tend to experience a bottom end lag, and small turbochargers spool up quickly but don't have the peak rpm bhp gains.

In the last 10 years the world of turbo chargers is always moving on and we commonly find variable vane turbo chargers, where the vane angle 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 push these at differently designed vanes in the turbocharger. They also improve the scavenging effect of the engine.

You'll commonly see there's a limitation in the air flow sensor MAP/MAF/AFM on the M52 when loads more air is being sucked into the engine.

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

Adding a supercharger or additional turbo will make large bhp gains, although more challenging to install. We have this in depth look at twinchargers if you want to read more.

Fuelling upgrades and mods

When you lift the bhp and torque you will need to increase to the fuel system.

More bhp and torque needs more fuel. It is important to over specify your injectors flow rate.

The rule of thumb is to add 20% when buying an injector, this allows for injector deterioration and affords 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.

Exhaust upgrades and mods

You may need to replace your exhaust if the existing exhaust is actually causing a restriction in flow.

On most factory exhausts you should find that 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 can usually air flow through the engine but do not go too large or you could will reduce the flow rate. Stick to 1.5 to 2.5 inches as a rule of thumb.

Typically exhaust restrictions come around the emissions filters installed, so adding a better flowing race alternative will help avoid this restriction.

Weak spots, Issues & common problem areas on the M52

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

Regular oil changes are vital on the M52, particularly when the engine has been modified and is putting down more power than the manufacturer intended.

For more information on Tuning your engine please join us in our friendly forum where you can discuss tuning options in more detail with our owners. It would also be worth reading our unbiased tuning articles to get a full grasp of the benefits and drawbacks of each modification.

History of the Engine

  • M52B20
  • 110 kW (148 bhp) at 5900 rpm 190Nm(140 lbft)  at 4200 rpm 1994-1998
  • M52TUB20
  • 110 kW (148 bhp)  at 5900 rpm 190Nm(140 lbft) at 3500 rpm 1998-2000
  • M52TUB24
  • 135 kW (181 bhp)  at 5800 rpm 240Nm(180 lbft)  at 3600 rpm 1998-2000
  • M52B25
  • 125 kW (168 bhp)  at 5500 rpm 245Nm(181 lbft)  at 3950 rpm 1995-1998
  • M52TUB25
  • 125 kW (168 bhp) at 5500 rpm 245Nm(181 lbft) at 3500 rpm 1998-2000
  • M52B28
  • 142 kW (190 bhp) at 5300 rpm 280Nm(210 lbft) at 3950 rpm 1995-1998
  • M52TUB28
  • 142 kW (190 bhp) at 5500 rpm 280Nm(210 lbft)  at 3500 rpm 1998-2000
  • S52B32 
  • 179 kW (240 bhp) at 6000 rpm 325Nm(240 lbft) at 3800 rpm 1996- 2000

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