Not all BMW 6-potters are the same. There are a total of four N5x engines in active use right now – the normally aspirated N52 and N53 as well as the turbocharged N54 and the N55. During European drive programs, the normally aspirated 6-potters that journalists get to try now are usually equipped with the N53 (from 08 plate onwards if I am not mistaken), which is a newer engine.
The new N53 comes in two displacements – 2.5 litres and 3.0 litres. One major difference with the N52 is that it comes with High Pressure Injection, which is basically direct injection. But the N53 does not have Valvetronic because there is not enough space in the cylinder head to implement both direct injection and Valvetronic. BMW has since solved this problem of course – in the N55 TwinPower Turbo they managed to put both Valvetronic and direct injection in that engine.
The N53B25U0 can make 190 horses at 6,100rpm and 240Nm of torque between 3,500 to 5,000rpm. The mid-range engine is the N53B30U0 which can produce 218 horses at 6,100rpm, and 270Nm of torque between 2,400 to 4,200rpm which is rather low by 3.0 litre standards, but the “U0″ 3.0 litre engine is detuned (used in ’25i’ products) and meant to compete with competitor products of a lower displacement/power output. The ‘proper’ 3.0 litre engine is the N53B30O0 which does the full 272 horses at 6,700rpm and 320Nm of torque from 2,750rpm to 3,000rpm.
Our recently launched F10 5-Series 523i comes with the N52 engine instead of the N53 engine. Power is 204 horses and 250Nm of torque, which is equivalent to the tune found in the Z4 sDrive23i. This is up from what the E60 523i had, but lower than what the 2.5 litre engine is actually capable of, so a little remapping trick in the future should be able to unleash those horses. The engine is older but I wouldn’t say it’s outdated as it is still in use in a few countries, not just our “ASEAN” country. USA and Australia still continues to use the N52 for the same reason that we use the N52 – high sulphur content in our gasoline. Yes, the sulphur issue is not just with our diesel.
According to BMW, they are able to introduce the N54 and N55 with direct injection here because the forced induction changes the combustion flame in a way that allows the injectors to be okay with the sulphur content here, but that’s as technical an explanation as I could get so far. It’s also because of the inability to offer direct injection here that we are stuck with the weak 156hp N46B20 engine in the 320i, when other markets have moved on to N43B20 with 170 horsepower and 210Nm of torque thanks to its direct injection system.
Personally I feel that the N52 sounds smoother and silkier than the N53, which sounds a little more growly and rough, likely because of the direct injectors. However the N53 feels punchier at the low end. Both have Double VANOS but the N53 has traded Valvetronic for direct injection, while the N52 has Valvetronic. If our F10 523i had come with an N53 engine instead of an N52, we would be looking at 204 horsepower at 6,100rpm and 270Nm of torque between 1,500 to 4,250rpm, which is a higher torque number over a much much wider RPM band, but N53 applications of the 523i carries a 3.0 litre engine displacement which would mean a significantly higher road tax in Malaysia.
Those are the facts that I have to share so far – if you know anything else about the N52 and the N53 please do share your knowledge in the comments area.