BMW N54
The BMW N54 is a twin-turbocharged straight-six petrol engine that was produced from 2006 to 2016. It is BMW's first mass-produced turbocharged petrol engine and BMW's first turbocharged petrol engine since the limited-production BMW M106 was discontinued in 1986. The N54 debuted at the 2006 Geneva Motor Show and was launched in the 335i model of the E90/E91/E92/E93 3 Series range. Following the introduction of its BMW N55 successor in 2009, the N54 began to be phased out. The final model powered by the N54 is the E89 Z4  roadster, which was produced until 2016. The N54 has won five straight International Engine of the Year awards and three straight Ward's 10 Best Engines awards. There is no BMW M version of the N54, however a high-output version of the N54 is used in the 1 Series M Coupe, 135iS, Z4 35iS and 335iS models. Design. The N54 was produced alongside the naturally aspirated BMW N53 engine; both engines have direct injection, double-VANOS (variable valve timing), an open-deck engine block and an electric water pump. Since the N54 is based on the older BMW M54  engine, it has an aluminium engine block (instead of the magnesium alloy used by the N53), a displacement of and does not have valvetronic (variable valve lift). Turbocharging is a key difference between the N54 and BMW's previous straight-six engines. The N54 has two small low-pressure turbochargers to minimise turbo lag. BMW's marketed the twin-turbo as "TwinPower Turbo", although the term has since been used for engines which have a single twin-scroll turbocharger. The N54's direct injection system (called "High Precision Injection" by BMW) uses piezo injectors. Its N55 successor uses solenoid-type  injectors, because the piezo injectors are more expensive and not reaching their full potential to obtain the "lean burn" benefit. Versions. All versions have a bore of , a stroke of , a compression ratio of 10.2:1 and the redline is 7000 rpm. 225 kW version. The initial version of the N54 is officially rated at and 400 N·m. However, these figures are considered to be under-rated, and independent testing has resulted in estimates of and . Applications: 240 kW version. A variant of the N54B30 with higher peak power and torque is used in the 2008-2012 740i and E92 335is . Applications: 250 kW version. The most powerful version of the N54 is found in the E82 1 Series M Coupe and the E89 Z4 sDrive 35is. Applications: Alpina. Biturbo engine by Alpina based on the N54B30, with upgrades including the engine control unit, oil cooler and pistons. 265 kW version. This is Alpina's initial version of the N54, producing . Applications: 294 kW version. Applications: 300 kW version. Applications: Critical reception. Car & Driver noted the N54 had minimal turbo lag and ""in feel and sound the twin-turbo could pass for naturally aspirated"". The N54-engined F01 740i was also  praised for its linear power delivery. Comparing the N54-engined E60 535i with the 550i (using a 4.8–litre naturally aspirated V8), one reviewer noted that the V8 model had more torque but was "only marginally quicker than the 535i" and that the additional weight of the V8 engine was noticeable on twisty mountain roads. High-Pressure Fuel Pump failures. In the United States, some N54 engines experienced failures of the High Pressure Fuel Pump (HPFP), resulting a class action lawsuit, a voluntary recall and an extended warranty for the HPFP. Failure of the HPFP can cause the engine to  suddenly stop functioning, which has caused several near-misses on highways. BMW was aware of HPFP problems, describing them in internal Technical Service Bulletins as "driveability problems". In April 2009, a class action suit was filed against BMW in connection with HPFP failures. BMW settled the suit in June 2010. On 26 October 2010, following an ABC News story about HPFP failures, BMW announced a recall of vehicles with the pump in question from manufacturing years 2007-2010. The recall was applied to 130,000 cars, resulting in the replacement of the HPFP in approximately 40,000 of these cars. In the  United States, the warranty period for the HPFP was increased to 10 years and . On some cars, the HPFP was replaced multiple times without resolving the issue, potentially leading to the car being refunded under the Lemon Laws in some states. Extended warranty in the United States. The High Pressure Fuel Pump issue caused BMW North America to extend the warranty for this pump to 10 years or . The warranty period for the fuel injectors was also increased, to 10 years or . An updated design for the fuel injectors was also introduced. Due to problems with rattling wastegates caused by  premature bushing wear, BMW extended the warranty period for wastegate-related issues to 8 years or . These warranty extensions only apply to the United States.