The UnixNerd's Domain - BMW N47 And N57 Diesel Engines

BMW N47 and N57 Diesel Engines

N57S 3.0 triple turbo, note timing chains at rear of engine

Chronology

BMW changed it's engine numbering system and in 2007 the M47 / M57 replacements emerged as the N47 / N57. The N47 was first used in the face lifted E87 one series but didn't make it's way into the E60 five series until late 2007 and the E90 three, X1, X3 a few months after that.

N47s are either 1600cc or two litre engines but the state of tune and certain component changes differ giving power outputs from 115bhp to 204bhp in the twin turbo 123d. The latter was the first ever production diesel to break 100bhp / litre when it was released in 2007. the 318d/118d are detuned two litres.

The 1600cc unit was used in the MINI One D at a detuned 95bhp and in the MINI Cooper D and 116d / 316d at 115bhp.

In 2008 the three litre N57 debuted in the E90 three series 330d replacing the M57. There were no 2.5 blocks, all 325d's were detuned three litres.

In 2009 the twin turbo arrived for the confusingly named F10 740d and in 2010 the new F10 five series 535d. It was also sold as an X5/X6 xDrive40d.

It's worth noting the the red line maximum rpm for these engines was lower for automatic cars, sometimes by over 1000rpm. For certain car and engine combinations there was no manual option, especially in the UK.

In 2012 a triple turbo 3.0 N57S shocked the market and made 376bhp / 550lb/ft of torque. This was sold as a 550d / 750d and in the X5 / X6. There was no V8 diesel replacement for the M67 4.4, the three litre triple turbo was seen as being enough which is probably a fair point.

BMW has sold this technology to Toyota so expect to see versions of the N47 in their cars for some time to come.

N47 fitted to a 320d.

Design

These engines were produced at a variety of power levels. In many cases the changes were mostly to the boost pressure (around 20psi) supplied by the turbo and the fuel rail pressure which varied from 1600 - 2000 bar. As before the turbos were electronically controlled variable incidence.

A major change from the older generation was the adoption of an alloy block with iron cylinder liners, this had significant stiffening webs in it's lower half. The longer M57 had a strengthening plate bolted to the bottom. The compression ratio was normally around 16.5:1 which was lower than before (it had been as high as 22:1 in the past). Certain models such as the N57S had no glow plugs and used modifications to the direct injection system instead.

The N57D30T0/1 models used twin turbos in series as the did the 123d's twin turbo N47. A small one to spin up quickly and reduce turbo lag then a larger one for the real boost. Amazingly the N57S used in the 550d had three!

Two litre N47s used twin balanced shafts to reduce vibration, a technique pioneered on the M43TU. The conrods and crankshaft were made from strong forged steel. The pistons skirts had a graphite coating to reduce friction. In a highly unusual move the timing chain is at the back of the engine which makes access difficult, see the problems section below.

Whilst the M47 had a fuel distributor the N47 uses common rail (like the Rover M47R) and used ceramic glow plugs to enable easier stop / starts in traffic to reduce emissions. For the same reason the alternator was a variable output unit with regenerative braking ability in pursuit of BMW's new Efficient Dynamics moto.

The 2010 update to the M57 saw the introduction of Bosch CRI 2.5 solenoid injectors which could deliver six injections per combustion cycle. The glow plug temperature was raised from 1000C to 1300C, hot! The new injection pump used 20% less power. There were more easily accessible swirl flaps and changes to both the catalytic converter and diesel particle filter (DPF).

From 2009 in some markets these engines used urea injection to reduce emissions. Basically most of the soot gets trapped in the diesel particle filter (DPF). Anything that doesn't is burnt in a secondary catalytic converter known as the SCR (selective catalytic reaction). When urea is injected into the SCR, a reaction occurs which generates ammonia (NH3). The ammonia reacts with nitrogen dioxide, converting it into nitrogen (N2) and water vapor (H2O). Downside is weight, expense, complexity and the fact you now have a DEF (diesel exhaust fluid) tank you need need to fill at oil service time or sooner. I'll stick to a petrol engine thanks. If the tank runs dry the car will refuse to start (it's a legal rather than technical block).

N57 in a six series

Variants

Code	Size	Power bhp@rpm	Torque lb/ft@rpm	BHP/litre	Torque/litre	Manufactured	Bore xStroke	Timing	Weight(kg)	VANOS	Used in
N47D16	1.6	95 @ 4000116 @ 4000	174 @ 1500-2750192 @ 1500-2750	6073	109120	2012 - 2013	78x83.6	Chain	?	No	MINI One DMini Cooper D, 116d, 316d
N47D20	2.0	143 @ 4000163 @ 4000177 @ 4000184 @ 4000	221 @ 1500-3000258 @ 1500-3000265 @ 1500-2750280 @ 1500-3000	71818892	110129132140	2007200920072010	84x90	Chain	?	No	118d/318d early120d/320d early118d/318d late120d/320d late
N47D20twin turbo	2.0	204 @ 4400218 @ 4400	295 @ 2000332 @ 1500-2500	102109	148166	20072011	84x90	Chain	?	No	123d
N57D30U0N57D30O0N57D30O1	3.0	201 @ 4000242 @ 4000254 @ 4000	330 @ 1750-2500400 @ 1750-3000410 @ 1500-3000	678185	110133137	201020082011	84x90	Chain	?	No	325d / 525d330d / 530d early330d / 530d late
N57D30T0N57D30T1N57S	3.0	302 @ 4400309 @ 4400376 @ 4000	440 @ 1500-2500460 @ 1500-2500550 @ 2000-3000	101103125	147153183	200920112012	84x90	Chain	?	Yes	535d / 740d535d / 335d550d / 750d

N57 3.0 twin turbo in an X5

Problems

If you're thinking of buying a diesel BMW check out the petrol vs diesel page first.

The enemy of all diesel engines is carbon deposits. The EGR valve which recirculates dirt through the engine to reduce emissions makes this worse. The first step for any poorly running diesel is to strip down the entire intake tract and clean it, especially the EGR valve. Many folk blank off the EGR valve but this may not be legal where you live.

Diesels take longer to warm up than a petrol engine and if run cold will get dirty very quickly as they don't burn off soot deposits. For this reason you really want to avoid cars that have been used only for lots of short journeys. They will seldom have reached normal operating temperature and will be filthy inside.

The other worry is the turbo, the only thing you can do to prolong it's life is to use good oil and change it at the correct intervals. Never let the level run low and let the car cool down gradually after very hard driving.

In most countries you'll have a Diesel Particle Filter (DPF). These store diesel soot and burn it off at high temperatures. Which is a problem if the car does lots of short journeys and never gets warm (seeing a pattern here?). If it clogs up it's an MoT failure and the car will drive poorly. Removing it may be illegal and a new one can be very expensive. All modern diesels have these, not just BMWs.

I'll bet urea injection causes issues once older cars stop being serviced at main dealers.

These engines are often chipped by their owners. Generally this isn't a bad thing and can have excellent results. But beware of used cars where things have been taken a bit too far.

If you drive this like a high performance engine it will drink fuel accordingly. For good economy it's best to be gentle and use the cruise control a lot.

Now the nasty one, the snapping timing chain saga. BMWs have normally been very good about this, but in the rare cases where it's happened a worn tensioner (easy and cheap to fit) was often the problem and a noisy chain should have given the game away. But they have been snapping in M47s in notable numbers. Failures on the M57 are much less common, possibly because it runs at lower revs due to higher gearing.

Updates in 2009 and 2011 both helped but have not completely cured the problem. In early 2015 BMW issued a recall to replace the tensioner and fit a new chain if it was worn. It seems the crank teeth were machined wrongly and over stretched the chain causing premature wear. The chain is at the rear of the engine so changing a suspect chain (actually two) is a much more expensive task than before as he engine has to be removed. Also the sprocket is machined directly onto the crank so you need a new crankshaft! Huge job. Don't buy a used one without some form of warranty and be certain it covers this.