BMW 3.0L N55 Turbocharged DOHC I-6

In the hands of a dangerous man like James Bond, the BMW 135is is a lethal weapon and the turbocharged inline-6 its blade, worthy of a third consecutive Ward’s 10 Best Engines win.

January 7, 2013

3 Min Read
BMW 3.0L N55 Turbocharged DOHC I-6

Something about the unflappable, unparalleled TwinPower 3.0L N55 inline-6, with its glorious exhaust note in the sporty BMW 135is, conjures images of a sophisticated man of the world in perfect shape rocking a tailored tuxedo.

Bond, James Bond, if he were German.

In the hands of a dangerous man like Bond, the 135is is a lethal weapon and the N55 its blade, worthy of a third consecutive Ward’s 10 Best Engines win.

After driving the 135is, WardsAuto editor David Zoia asks a simple question on his score sheet: “What more do you need? This engine is near perfection.” Zoia goes on to give the 320-hp N55 a perfect 20 out of 20 points in ranking its power and adds, “Eeyow!”

Fellow editor Christie Schweinsberg likewise gives the N55 perfect scores for both power and torque and writes, “It’s always there when you want it. It’s never wanting.”

The 135is presents a more potent version of the N55, producing 317 lb.-ft. (430 Nm) of torque. Output the past two years was limited to 300 hp and 300 lb.-ft. (407 Nm).

We’ve raved about the eagerness of BMW’s 2.0L turbo 4-cyl., and the N55 I-6 is even better, achieving maximum thrust at a mere 1,200 rpm and able to sustain it until a staggering 5,000 rpm. The N55 sets the tachometer needle dancing frantically and does more work by 2,500 rpm than most engines do at wide-open throttle.

Even with the additional power, the N55 in the 135is achieves the same emissions levels and fuel-economy ratings (20/28 mpg [11.7-8.4 L/100 km]) as the 300-hp iteration.

The 135is is lighter than the 3-Series we evaluated with this engine last year, allowing near immediate response when the accelerator is depressed, actuating not a throttle but instead triggering an electric motor in BMW’s proven Valvetronic intake system to continuously vary the amount of valve lift for optimum breathing.

Not to be overlooked is BMW’s passionate embrace of the inline architecture while other auto makers use V-6s. Benefits include lighter weight, supreme smoothness and lower friction compared with a V-6 of the same displacement.

And despite its tall, lean stature, an I-6 provides packaging advantages when forced induction is added. Fritz Steinparzer, BMW's head of gas engine development, tells WardsAuto this past summer the best configuration for a boosted engine is to place the intake on one side and the exhaust manifold and turbocharger on the other.

The N55 also powers a BMW that did not make the cut for Ward’s 10 Best Engines this year, the ActiveHybrid 3-Series.

This turbocharged, direct-injection 6-cyl. engine is meant to run hard, not be tempered by a balky stop/start system and electric motor or be shackled by the mass of 96 extra battery cells. Like a stealthy secret agent, the N55 works best alone.

But BMW, rightfully so, has ultimate faith in this engine’s attributes, now placing the higher-output N55 in the flagships, the ’13 740i and 740Li.

In these applications, the torque is tweaked even higher, to 332 lb.-ft. (450 Nm), enabling a sprint to 60 mph (97 km/h) in less than 6 seconds and proving that every mission is possible for the N55.

Moral of the story: Good triumphs over bad, when German intelligence is on the case.

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