BMW N52 Tuning (N52B25 & N52B30)

"All you need to know about performance tuning the BMW N52 engine!"

The N52 replaces the M54 and had a lighter engine block, an electric water pump and variable flow oil pump. Valvetronic was also added. The camshaft is also of a hollow design, to save weight.

The engine is controlled through a Siemens MSV70 ECU. Don't dismiss this engine just because it is a NASP unit, it has lots of tuning potential and is a really nice silky smooth engine to drive.

Thankfully there are quite a few people out there playing the N52 and as a result, we see some impressive turbo conversions and power upgrades on this really well designed and built engine.

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Depending on where you are in the world your experience will vary, as emissions regulations will often limit your tuning options and not all mods are legal in all areas.

It's always interesting to see what people do in other countries, here in the UK, we have access to a wide selection of parts directly from Germany. In some regions though the availability of cams and turbo kits is scarce and restricts your options to intake, exhaust, and mapping mods.

As an international forum, we feel we are well placed to give the best overview of what is possible on your N52 engine and TorqueCars are not sponsored, so you'll only get honest unbiased advice from me.

History, Power & Specs of the N52 Engine

There were 2 versions, the N52B25, and N52B30. The differences between these engines are the N52B25 has a smaller bore and stroke, so pistons, crank, etc are different, but they share the same block and head.

NB: The N51 is almost indistinguishable from the N52 but was made to conform to tougher emissions regulations and standards (SULEV).

Hi there, the N52 is a pretty popular engine and it's nice to be looking at a NA (naturally aspirated) engine. It is a lighter magnesium and aluminum alloy block so that weight saving just adds to the overall package.

The N52 was a straight 6 NA (naturally aspirated) engine  and won a Wards best engine award in 2007 and 2006. It also had double VANOS. The intake manifold from the 330i with DISA valves is much better than those fitted to other N52 engines

N52B25 specs

• 174 bhp @5,800 rpm 170 lbft @3,500-5,000 rpm 2005-2008
• 201 bhp @6,400 rpm 184 lbft @2,750 rpm 2007-2011
• 215 bhp @6,500 rpm 184 lbft @2,750-4,250 rpm 2005-2011

N52B30 specs

• 215 bhp at 6,100 rpm 199 lbft at 2,500-4,250 rpm 2006-2010
• 215 bhp at 6,100 rpm 207 lbft at 2,500-3,500 rpm 2010-2011
• 228 bhp at 6,500 rpm 229 lbft at 2,750 rpm 2008-2011
• 241 bhp at 6,500 rpm 229 lbft at 2,750 rpm 2008-2011
• 255 bhp at 6,600 rpm 221 lbft at 2,500-4,000 rpm 2010-2011
• 255 bhp at 6,600 rpm  229 lbft at 2,600 rpm  2009-2015
• 261 bhp at 6,600 rpm 232 lbft at 2,750-4,250 rpm 2005-2009
• 268 bhp at 6,650 rpm 232 lbft at 2,750 rpm 2006-2010

N51B30 SULEV compliant engine

The N51 was built to conform to SULEV requirements and featured the DISA "variable-length intake manifold" with 3 stages instead of 1, and the engines compression ratio was lowered from 10.7:1 to 10.0:1

Best N52 (N52B25,N52B30) tuning mods

The greatest mods on an engine are in our opinion the ones that give the best power gain for your spend. Generally speaking, the higher power cars already have a good setup so improvements, although minimal will still offer a better final power figure than on the lower models.

But if you choose your N52 mods carefully you can close the gap, and end up with a really nice engine, and bucket loads of torque.

We won't be swayed by popular N52 mods, they need to be cost effective, and give a good driving experience.

Altering your N52 camshaft will make a dramatic difference to the engine bhp. Choosing a higher performance camshaft profile raises the bhp accordingly. As the stock cams are hollow you can't easily get them reground but there are specialists out there in Europe offering some nice cam options.

Fast road cams usually increase the torque over the rev range, you may sacrifice a little low down torque but your higher rpm power will improve.

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

You'll never have found a Race camshaft is a pleasure to live with when on the daily commute, because the lumpy idle will make the car prone to stall and smooth driving at low rpm becomes impossible. If you are developing a track car this doesn't matter as you are in the high end of your RPM range anyway and that is where you want the power to be.

Some N52 engines (N52B25,N52B30) respond better to more or less aggressive camshaft durations check your engine on a rolling road. Generally speaking the lower power engines from the factory will give better gains from a revised cam. It seems there is more scope for improvement with them, and BMW did a better job setting up the B30's.

The engine timing and fuelling (remapping) also will provide better bhp gains after fitting a cam, and some head work including larger valves and a 3 or 5 angle valve seat job will further improve your gains.

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.

Modification stages for the N52B25 & N52B30

Please watch our video which covers the 5 principles of tuning your car. Be sure to keep up with our latest YouTube content and subscribe.

Best mods for your N52

1. ECU Tunes - A Remapped N52 ECU offers the biggest gains for your outlay, replacement ECUs, and piggyback ECUs are all alternatives.
2. Turbo upgrades - forced induction is the most efficient approach to improve intake air supply, ensuring you are able to utilize more fuel and make better power figures. It is one of the most technically difficult modifications but provides the best gains.
3. Air Induction kits and Exhaust - Please be warned on their own these mods will NOT ADD TORQUE , but they can help enhance power after other upgrades by lessening the restriction.
4. Low mass flywheel - a reduced weight flywheel will enhance the engines ability to rev freely. Not always recommended for all N52 engines.
5. Fast road cams are significant power adders, but we recommend they be fitted by someone qualified to set them up and some cams are hard to find but there might be a local firm to regrind a stock cam for you.
6. Internal engine mods - crank, pistons, conrods & compression ratio including balancing and blueprinting

N52 Tuning Stages

Typical stage 1 mods often include: Sports exhaust header/manifold, Remaps/piggy back ECU, drilled & smoothed airbox, Fast road camshaft, Panel air filters, Intake manifolds from the 330i.

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

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

ECU flashing allows a tuner to establish the full potential of all the upgrades you've fitted to your N52 so it is best to do that last so all of your other mods can be taken into account.

Remapping the car is one of the best mods for most cars and no exception on the N52, who to go to depends on where in the world you are, and there are lots of specialists around. Our forums are a great place to find out what other people have used and their experiences, so please drop in and say hi.

Don't pay too much attention to the peak power gains quoted, the torque curve is what you should pay attention to the most. 15hp is generally the extra power you'll have to play with after a remap.

Tuning boxes are also available for these, which are easier to fit and remove than a tune/remap but the gains are not quite as impressive, with around 10hp more.

N52 intake manifold upgrades

It is vital to any tuning job to pull more air into each cylinder.

The intake manifold from the 330i is much better than those fitted to other N52 engines, it flows more air and better directs this air, and you really feel this improvement at the top end of the RPM range, so it makes sense to source one of these and swap it out.

Power gains for this simple mod can range from 22hp to around 30hp depending on the base model with the 325i making more power. Air filter improvements are negligible at around 5hp, but it will give a nice intake sound.

The DISA valves are quite an impressive innovation and ensure the fresh intake air is directed exactly to the cylinders which require it, this avoids much turbulent flow associated with a conventional intake design.

Increasing the N52 valve size, carrying out port matching and head flowing will also raise power, & more importantly, will afford you an improved power increase on other parts.

N52 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 N52.

A centrifugal supercharger seems very well suited to the N52, and provides a linear power delivery, they are also easier to setup than a turbo when it comes to mapping them.

Top mount turbos are generally easier to install rather than going with a low rear exhaust mounted turbo where space is limited to the smaller turbo units. You will need a custom manifold, and although the N54 and N55 heads look similar there are notable differences, namely the water inlet and the location of the aircon compressor which affect the design.

Sacrifice your aircon and you make life a little easier, but why do that when there are lots of suitably modified manifolds out there you can use.

But adding forced induction is the only way to make significant power gains on both the N52B25 and N52B30, as the engines are quite well set up from the factory, leaving little room for improvement without resorting to major upgrades and work.

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

When an engine has a turbocharger parts are more reliable and you will discover turbocharged engines will have many forged and stronger components.

However, you'll find engines typically have weak spots or components that are more prone to fail. So discover these restrictions, and upgrade to more solid crank conrods and pistons to handle the power.

We've seen people spending a loads on turbo charger upgrades on the N52 only to have the car catastrophically fail just after it's been enthusiastically driven because they are running too much boost or haven't done the mapping properly.

Depending on your engine's compression ratio the feasibility of adding a turbo varies, with lower compression engines happily running around 1 bar of boost.

For a street car we would recommend a BorgWarner EFR turbo 6258 should be good for around 400bhp and the 6758 takes you to 450 but has more low end lag. (The intake and compressor wheel size forms the BW model number)

There is also a kit that comes with a GT3076R which is good for around 70hp more from Laurent motors which we have yet to try out but the specs seem good to us.

You really want boost to come in at 2000rpm and hit peak around 5000rpm.

Larger upgraded turbochargers commonly suffer no power at low rpm, and small turbochargers spool up quickly but don't have the high rpm bhp gains.

Bimmer Performance Center did an interesting 71-63 turbo, that could potentially boost to around 500hp on the N52, and you could always swap in turbos from the N54 or N55 for around 300-400hp.

It is not unusual that there is a limit in the airflow sensor MAF/MAP on these engines when loads more air is being drawn into the engine.

You'll see that 4 bar air sensors cope 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 bhp gains, although more difficult to get working. We have a twincharger bhp adding guide if you want to read more.

N52 fuelling upgrades

When you raise the bhp and torque you will need to pay attention to the fuelling. Thankfully the stock fuelling on the N52 is good for around 300bhp in most cases.

It really is as simple as more bhp and torque needs more fuel and air. We would recommend you to be generous with your flow rate on the injectors. The M3 injectors are a good route to go to increase fuelling especially if you are adding more boost.

The accepted safe increase is to add 20% when buying an injector, this accounts for injector deterioration and affords some 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.

N52 Exhaust upgrades

You only need to improve your exhaust if your current exhaust is actually causing a restriction in flow.

Exhaust mods will generally net around 5hp more power, and sports cats and decat options will help release more power than just a straight exhaust swap.

Note that with the largest exhaust you can buy this will slow the exhaust rate - the best exhausts for power gains are usually between 1.5 to 2.5 inches. It is the shape and material more than the bore size.

More gains are to be had in replacing the headers than just doing a cat back exhaust system, but for that nice exhaust note you should think about a full system.

Usual exhaust restrictions come around the emissions filters installed, so adding a better flowing sports alternative is the answer. This keeps the car road legal and will flow much better due to it's higher internal surface area and design, so has the added benefit of keeping your car road legal.

In some areas it is even technically illegal to remove a catalyst and replace it with a performance one, unless it has failed or is faulty, so please check your local laws on this.

The alternative decat should be considered an off road only mod, as removing a catalyst is illegal in most territories and regions for road registered cars.

Weak spots Issues & problem areas on the N52

The engines are generally reliable and solid units, as long as you follow the manufacturers service schedules, and use a good quality oil to ensure longevity. Few problems should happen as long as they are regularly serviced and maintained.

Carbon build up in the head, particularly around the valves which will sap power or create flat spots, this is a larger issue on direct injection engines but should be looked out for on all engines. We have tips on removing carbon build up.

Some of our members have had issues with flat spots or glitches after applying mods and upgrades or tuning, this is not usually related to this engines design, so instead see our article on diagnosing flat spots and problems after tuning which should help you get the bottom of this issue.

There are issues with lifter/tappet noise due to a lack of oil pressure

There was a recall following a fire risk from the crankcase ventilation valve shorting, this was back in 2017 so most will have had the recall work done now.

Regular oil changes are vital on the N52, especially when tuned, and will help extend the life and reliability of the engine.

If you would like to know more, or just get some friendly advice 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.

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This article is flagged for an update, so please pass on specific tips below that I can include. All articles, and content was written by me, Waynne Smith TorqueCars founder. Some outlines are just too general so I appreciate your feedback and suggestions. This entry was filed under BMW. You can leave a response below or join our forum to discuss this article and car modification in detail with our members.

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