BMW N47 vs B47: Comparing Two Diesels

Introduction

The N47 (2.0d, 2007–2014) earned a reputation as “the diesel with the timing chain problem.” No other BMW engine did as much damage to the brand’s image. The B47, its successor from 2014, was built as a targeted rework of exactly those weak points: a more robust timing chain, revised injectors, an improved EGR system, and a new block. Below is what BMW actually changed, whether the B47 truly solved the chain problem, and which diesel makes more sense on the used market.

Technical Comparison

Parameter	N47	B47
Layout	Inline-4 diesel	Inline-4 diesel
Displacement	1,995 cc	—
Power	143–218 hp	up to 231 hp (25d)
Torque	258–332 lb-ft	280–295 lb-ft (typical), up to 428 lb-ft (25d)
Injection	Bosch Piezo CRI3	Bosch Solenoid CRI4
Timing chain	Flywheel side, narrow (weak point)	Front side, wide, reinforced tensioner
Emissions class	Euro 4/5/6 (early)	Euro 6d-Temp, Euro 6d (late)
Production period	2007–2014	from 2014
Rated consumption	43–52 mpg	lower at higher output

The dense set of tightening torques and torque figures is consolidated in the table below — not a single value is lost.

Torque Specifications

Configuration	Torque
N47, full range	258–332 lb-ft
B47, typical 320d/520d (184 hp)	280–295 lb-ft
B47 25d (231 hp)	up to 428 lb-ft
Stage 1, gain for both engines	+44–74 lb-ft

At comparable power levels (320d/520d, 184 hp), both engines deliver a similar 280–295 lb-ft, but the B47 has a wider torque plateau — 1,600–3,000 rpm.

Design Differences and Their Causes

The key difference lies in the timing chain’s location. The N47 was developed in 2007 as the successor to the proven M47, with the goal of making the engine more compact and lighter. To achieve this, BMW moved the chain from the front (timing drive) side to the flywheel side. This saved packaging volume but had a fatal consequence: the chain is only accessible by separating the engine from the transmission.

That layout turns a routine job into a labor-intensive one: shop time grows from 4–6 to 12–18 hours. On top of that, the N47’s chain is narrower by design, and its hydraulic tensioner is weaker than the previous generation’s. With long oil change intervals (BMW LL-04, 16,000–19,000 miles), chain wear accelerates.

The B47 brings three fundamental changes. First — the timing chain moved back to the front side (as on the classic M47), so it’s accessible without pulling the engine. Second — the chain was made wider and the tensioner reinforced; the link material and geometry were borrowed from the inline-six N55, where the solution had already proven itself. Third — the injectors switched to Bosch CRI4 Solenoid instead of CRI3 Piezo: solenoid units are simpler to control, mechanically less prone to coking, and roughly 30% cheaper to replace. The B47 also got a revised EGR cooler (after problems in the first 2014–2017 series, it was modified again) and, from the 2017 model year, an updated SCR system with AdBlue.

Development History

The N47 was produced from 2007 to 2014 and dominated the used diesel BMW market of that period: E90 320d, E60 520d, F10 520d, F30 320d, X1 18d/20d, X3 20d. The design goal was compactness and lower weight compared to the M47.

The B47 has been in production since 2014 and is still current, fitted to the F10 LCI, F30 LCI, G20, G30, X1 F48, X3 G01. Rule of thumb: diesel BMWs from the 2015 model year onward are B47s.

Common Failures

N47

Timing chain — the main problem. The classic N47 defect. It starts with a rattle on cold start, then becomes constant; a broken chain means engine damage. Signs: cold-start rattle from 50,000 miles, constant rattle from 93,000 miles, then risk of a snap with a rebuild. BMW repeatedly repaired under goodwill but never announced a full recall.

Bosch CRI3 Piezo injectors age, and imprecise injection causes knocking, black smoke, and higher fuel consumption. Replacement is followed by IMA coding.

EGR system and swirl flaps. The EGR valve cokes up after 93,000 miles. Swirl flaps in the intake manifold can break off and enter the combustion chamber — risk of engine damage. A preventive inspection is recommended.

DPF clogging on short trips. As with any modern diesel: when driving mostly distances of up to 9 miles, regeneration doesn’t trigger, the diesel particulate filter (DPF) clogs, and limp mode kicks in.

B47

EGR cooler crack in the first series (2014–2017): coolant enters the intake tract, triggering limp mode. BMW introduced a revised version; check the index when buying.

AdBlue system (from 2017): NOx sensors age, and the dosing module can fail. This isn’t a structural “killer” but a serviceable part.

More complex sensor electronics make diagnosis without ISTA harder.

Failure Summary Table

Failure	Engine	Typical mileage	Consequence
Timing chain	N47	from 50,000 miles	engine damage
CRI3 injectors	N47	as wear occurs	knocking, smoke, consumption
EGR, swirl flaps	N47	from 93,000 miles	engine damage
EGR cooler crack	B47 (2014–2017)	—	limp mode
NOx sensors, AdBlue doser	B47 (from 2017)	—	SCR faults
DPF clogging	both	short distances	limp mode

Diagnostics and Pre-Purchase Inspection

Checking an N47 centers on the timing chain. Cold start: the car should sit for 12 hours, then audio is recorded for 10 seconds after startup. Any rattle lasting longer than 3 seconds means a repair is coming. Service history: the oil change interval should be under 16,000 miles, oil grade LL-04; cars with exclusively “Long Life” records are problematic. Paperwork: ask the seller whether the chain was replaced, with the service invoice — line items “timing chain kit,” “engine and transmission separation,” “flywheel,” or “tensioner kit.” A test drive on the highway reveals limp mode symptoms, hesitation, and power loss — signs of injector or EGR problems.

Checking a B47 focuses on the EGR cooler index (versions before 2018 are problematic) and the AdBlue system’s operation (sensors).

Shop Experience

According to workshop statistics, the B47 shows roughly 60% fewer engine failures per 62,000 miles than the N47, and a correspondingly lower rate of unplanned visits beyond scheduled maintenance. For the N47, shops record 3–5 times more timing chain repairs than for a comparable M47 or the B47.

With an intact chain, the N47 remains a high-revving diesel with good responsiveness. Its advantages also include no AdBlue system on versions before the Euro-6c tightening, a huge model range, and high parts and repair expertise availability.

Reliability

The B47 is substantially more reliable than the N47. The main problem — the timing chain — was solved by design. Both engines last 155,000–186,000 miles with careful maintenance, but the B47 carries lower risk. In the first 124,000 miles, the B47 chain typically shows nothing; the first isolated signs of wear appear only after 155,000 miles.

Tuning

Both engines respond to Stage 1: +30–50 hp and +44–74 lb-ft. But tuning the N47 disproportionately raises timing chain risk — that modification isn’t recommended. Tuning the B47 is statistically non-critical; Stage 1 runs without consequences. Diesel tuning makes sense for the torque gain, not peak power.

Buying Recommendations

N47. Always check the cold-start sound. With a documented chain replacement, the main risk is considered resolved. If the chain hasn’t been replaced — budget a financial reserve for the repair and get written confirmation from the seller that the chain wasn’t replaced. A preventive chain replacement makes sense on a car with 93,000–124,000 miles and an intact chain if you plan to drive another 62,000+ miles. If you plan to sell the car in 2–3 years, preventive work isn’t economically justified — better to go straight for a B47.

B47. Check the EGR cooler index (versions before 2018 are problematic) and the AdBlue system for fault codes. Early 2014–2017 series are best avoided due to EGR cooler risk; from the 2018 model year, the engine is strongly recommended.

For those driving 19,000–37,000 miles a year, mostly on the highway, the B47 suits noticeably better. Check the AdBlue tank capacity (typical — 25 liters, range about 9,000–12,000 miles), monitor NOx sensors at service, and check EGR operation every 62,000 miles. With those three points covered, the B47 is the economical choice for long-distance driving.

FAQ

How serious is the N47 chain problem?

In workshop statistics, the N47 has 3–5 times more timing chain repairs than a comparable M47 or its successor, the B47. In the worst case — engine damage requiring a rebuild or replacement. The risk should be factored into the purchase.

Has the chain problem been solved in the B47?

Largely yes. The design changes (front side, wider chain, reinforced tensioner) statistically eliminated the problem. In the first 124,000 miles, the B47 chain usually shows nothing; isolated signs of wear appear only after 155,000 miles.

Which engine has better torque?

The B47 in its strongest versions (25d, 231 hp) — up to 428 lb-ft, more than any N47 version. At comparable power (320d/520d, 184 hp), both are close — 280–295 lb-ft, but the B47 has a wider torque plateau (1,600–3,000 rpm).

How do you spot an N47 chain replacement when buying?

A service invoice with line items “timing chain kit,” “engine and transmission separation,” “flywheel,” or “tensioner kit.” At a BMW dealer, you can request VIN-based information on whether such work appears in the service history.

How much AdBlue does a B47 use?

Typically 1.0–1.5 liters per 620 miles. At 12,000 miles a year — about 25–30 liters. Top-ups are done at the shop or DIY from a jug.

Which models came with the B47 from the factory?

F10/F11 520d LCI (from 2014), F30/F31 320d LCI, F20 LCI 118d/120d, F22 220d, F32/F33 420d, F25 LCI X3 20d, F26 X4 20d, F15 X5 25dX, F48 X1 18d/20d/25dX, G20 320d, G30 520d, G01 X3 20d, G05 X5 25dX. Rule: diesel BMWs from the 2015 model year onward are B47s.

Takeaways

The B47 is the preferred choice: the timing chain moved to the front side, made wider with a reinforced tensioner, injectors switched to Bosch CRI4 Solenoid, and the EGR cooler and AdBlue system were refined. The N47 is only justified with a documented chain replacement. Before buying, check the cold start and service history — that’s the only reliable way to separate a car with remaining life from a potentially problematic one.