The 340i is an all-new turbo inline six making 320 horsepower, replacing the 300-hosepower motor in the now-defunct 335i.
BMW must be sandbagging, because the B58 has got punch across entire powerband; it goes from zero to 60 in 4.8 seconds while the M5 gets there a full second and a half later. They’re polar opposites in character, and depending on how you like your motors the S38 is either too raw or the B58 too refined.
Individual throttle bodies and a single-mass flywheel make the M5 revs snappy, and the raspy grunt at full throttle is reminiscent of an old Merlin engine from a Spitfire. It lacks the civility of newer motors though, and at stoplights you’ll hear gearbox chatter and a lumpy idle.
The 340i may lack the soundtrack of the E34 but it’s one of the best inline sixes in recent years from BMW.
It quietly hums in traffic, and changes to a coquettish roar when romping on the throttle, thanks to a well-insulated cabin that necessitates fake engine noises piped through the speakers.
The M5 may sound better—it’s got one of the best engine notes of the classic Big Sixes—but the 340i sings all the way to its 7400 rpm redline without a hint of turbo lag, and is superior by all objective counts. Advantage: 340i.
While rose-tinged nostalgia may apply for the inlines of the past, it’s a mismatch to compare old and modern transmissions.
The five-speed Getrag 280 in the M5 heaves into each gear with a mushy takeup and long throws, and the gearbox isn’t is stout as other offerings, like the Getrag 265 in the E30 M3. Early models have a shorter final drive and are sportier, but cruise at higher rpm (the six-speed was never offered in North America).
The six-speed only offered in the Euro ’95 M5s provided an extra gear for cruising, but still had similar characteristics, with play that quickly develops in the shifter mechanism.
On the other hand, you can’t go wrong with either the six-speed manual or the eight-speed ZF in the 340i. The manual effortlessly shifts with a lighter clutch than the 1991 E34 M5, and standard transmissions can’t touch the shift speeds of the automatic. Advantage: 340i.