BMW N54

BMW N54 engine
Overview
Manufacturer	BMW
Production	2006–present(2015)
Combustion chamber
Configuration	Straight-6
Chronology
Predecessor	BMW M54, BMW N52
Successor	BMW N55

The BMW N54 is a direct injection turbocharged straight-6 DOHC engine^[1] which began production in 2006 and presently (2015) remains in production in the E89 Z4 sDrive 35is. It debuted at the 2006 Geneva Motor Show and was launched in late 2006 in the E92 335i. The N54 began to be phased out following the introduction of the N55 in 2009.

The N54 has won five straight International Engine of the Year awards,^[2] and three straight Ward's 10 Best Engines awards.^[3]

Models

N54B30 (225 kW version)

For the E90/E91/E92/E93 3-Series, the N54 engine was used in the 335i model from 2007 onwards. In the 3-series, it therefore replaced the 330i (which used the naturally aspirated N52B30 as the performance model below the M3).

This version is rated at 225 kW (302 hp) and 400 N·m.^[4] However, independent testing has resulted in estimates of 332 hp (248 kW) and 311 lb·ft/422 N·m.^[5]

Applications:

• 2007–2010 E60 535i
• 2007–2010 E90/E91/E92/E93 335i
• 2007–2010 E82/E88 135i
• 2008–2010 X6 xDrive35i
• 2009–2016 Z4 sDrive35i

N54B30 (240 kW version)

A variant of the N54B30 with higher power and torque (but a slight reduction in low rpm torque) is used in the F01 740i^[6] and E92 335is.^[7][8]

Applications:

• 2008–2012 F01 740i
• 2010–2013 E92/E93 335is

N54B30TO (250 kW version)

The most powerful version of the N54 is found in the E89 Z4 sDrive 35is (as of 2016, the only application of the N54 still in production) and the 1 Series M Coupe.^[9][10]

Applications:

• 2011–2012 E82 1-series M Coupe
• 2011–2016 E89 Z4 sDrive35is

Design

Unlike the (naturally aspirated) N52, N53 and (turbocharged) N55, the N54 does not use variable valve lift (called valvetronic by BMW) or a magnesium alloy block. This is because the newer N52 aluminum-magnesium engine block was not deemed as suitable for turbo-charging with the above-mentioned engineering goals. Instead, the N54 engine is based on the older BMW M54 engine.^[11] It therefore features an aluminium construction and variable valve timing to both camshafts (called dual VANOS by BMW). Differences between the M54 and N54 include twin turbochargers, an intercooler, direct injection, a closed-deck single-piece block and an electric water pump.^[12][13] As per the M54B30, the N54 has a capacity of 2,979 cc (182 cu in). With a weight of 195 kg (430 lb), the N54 is 34 kg (75 lb) heavier than the N52.

The engine uses two small low-pressure turbochargers to minimise turbo lag. The boost pressure is 8.8 psi, because BMW's goal was to offer the same driving feel as with naturally aspirated engines.^[14] BMW's term for turbocharging is "TwinPower Turbo",^[15] which has also been applied to the N55, which uses a single turbo (but with twin-entry turbine housing).

The engine's direct injection system uses piezo injectors, as per the naturally-aspirated N53. The N55 engine uses solenoid-type injectors, because the piezo injectors are more expensive and not reaching their full potential to obtain the "lean burn" benefit.^[16] BMW's trademark for direct injection, regardless of type, is known as "High Precision Injection".^[17]

Performance

Comparison with 6-cylinder engines

The N54 has considerably higher horsepower and torque, compared to BMW's recent straight-6 engines which were all naturally aspirated such as the high output versions of the N52B30 (which has the same displacement as the N54), with the N54 having an additional 45-horsepower and 80 pound-feet of torque over the N52B30.^[18]

BMW's newer N55 3.0L turbo inline-6 uses a single turbocharger but with twin scroll technology, and its 300 lb-ft of torque comes at 1200 rpm which is 200 revs earlier than the N54’s identical output.^[19] The N55 is also more fuel-efficient and has less emissions than the N54. However, the N54 engine has more output potential and a variant of the N54B30 with higher power and torque but a slightly narrower powerband is used in the F01 2009 BMW 740i.^[6][20] A comparison test saw the 2011 BMW 740i accelerate quicker than the 2011 BMW 535i (equipped with the N55), even though the 535i weighs 300 pounds less.^[21]

The use of two small turbochargers plus direct fuel injection allows for a broader power band and less turbo lag than previous turbocharged gasoline engines. Despite its relatively small-displacement, the N54B30 provides the midrange torque of a mid-displacement V8 engine more efficiently and at less weight.^[22]

Comparison with V8 engines

The torque characteristic of the N54 engine combined with the relative lack of turbo lag provides a similar feel to a small V8, according to a journalist.^[22] The advantage of the N54B30 engine is that compared to similar power output 225 kW (302 hp) 290 lb·ft (390 N·m) V8 4.0L N62B40 it weighs 70 kg less than the V8, which is massive at 265 kg (584 lb). Additionally, the N54 has higher low-end torque than the N62B40. In the 5 Series (E60), the N54 in the 2008 BMW 535i gives it almost equivalent acceleration to the BMW 550i, with a V8 engine (4.8L N62B48) which costs an additional $10,000 USD in MSRP and makes the front 200 pounds heavier.^[23]

In the 2011 BMW 740i, the N54 is down 85 hp (63 kW) and 120 lb·ft (160 N·m) compared to the BMW 750i’s N63 4.4L twin-turbo V8, however the 740i weighs about 215 pounds (98 kg) less, which considerably improves handling dynamics.^[24] The 740i also retains respectable straight-line acceleration in a comparison test as it could make the 0 to 60 mph (97 km/h) run in 5.1 seconds compared to the 750i's 5.2, and the 750i only catches up at 70 mph (110 km/h), with the N54 having less turbo lag, smoother acceleration, and smoother power delivery than the N63.^[25] Fuel economy of the 740i is 17 mpg city and 25 highway, compared with the 750i’s 15/22 and the ActiveHybrid 7's 17/26, considering that the 740i has an MSRP of $71,025 USD while the ActiveHybrid 7 (which shares the N63 V8 with the 750i but mated to an electric motor) starts at $103,125 USD.^[26]

Common Problems

HPFP Failure

In at least the US market, the N54 engine has been characterized by a very large number of High Pressure Fuel Pump (HPFP) failures,^[27] leading to BMW North America vehicle Lemon Law "buy backs" and reduced customer goodwill.^[28] BMW's failure to solve the HPFP problem has led to serious safety concerns over dangerous sudden losses of power at highway speeds.^[28] Reports of drivers being stranded are not uncommon and some have accused BMW of actively concealing the problem rather than addressing it.^[28] On 26 October 2010, BMW announced a recall of vehicles with the pump in question from manufacturing years 2007–2010.^[29]

In April 2009, a class action suit was filed against BMW in connection with HPFP failures.^[30] BMW settled the suit in June 2010. On 26 October 2010, following an ABC News story about HPFP failures,^[31] BMW announced a recall of vehicles with the pump in question from manufacturing years 2007-2010.^[32]

Turbocharger Failure

The N54 turbochargers have been known in at least the U.S. and Canada to suffer from premature wastegate bushing wear which results in an audible wastegate rattle noise. If the wear is severe enough the wastegate will not seat properly resulting in a loss of boost pressure and trigger engine fault 30FF which temporarily reduces power output. BMW North America (which does not manage the Canadian market despite its name) recognized the design flaw and extended the warranty period for US vehicles to 8years/ 82,000 mi for wastegate related issues only.^[33] BMW Canada (which does manage the Canadian Market) does not offer any relief for turbocharger wastegate rattle issues in Canada beyond original warranty.

See also

• List of BMW engines
• BMW M54
• BMW N55

References