Naturally aspirated engines from BMW are not long for this world. In fact, at the time of this writing, the only two ways you can have a straight six au naturel is by ordering a 128i or, like our long-termer, an X3 xDrive28i. Soon, the faithul 3.0-liter mill will be replaced by the turbocharged 2.0-liter I-4 that is now powering the base 528i, 328i, and Z4 sDrive28i.
The engine is codenamed N20, and by all appearances it should be better than the six in every regard. Piling direct injection on top of variable valve timing and a twin-scroll turbocharger has netted BMW more power and better fuel economu in a package that is smaller and lighter than the outgoing straight-six.
Take the new 328i, for example, which I spent a good amount of time in last month. Over last year's model, the N20-powered 3 Series delivers 10 more horsepower 1500 rpm sooner and 55 pound-feet of torque 1500 rpm sooner. On top of that, the sedan also sees a fuel economy increase of 6 mpg city and 8 mpg highway, some of which we can attribute to the sedan's new 8-speed automatic.
Drive impressions? Aside from a diesel-like clatter at idle, we found it hard to make an argument against the N20. As the figures suggest, power arrives nice and early, improving low-speed drivability. More importantly, the lighter four-cylinder gives the nose a greater sense of agility. After back-to-back drives with the 335i, we found that the 328i felt lithe and a bit more flexible in comparison. On the side of a curvy road, we debated the merits of extra power versus the lighter nose.
While the X3 doesn't corner with the same ferocity (it's not far off though), it will reap the same benefits that the 328i does. Official EPA figures aren't out yet, but BMW expects that the N20-powered X3 will be the most fuel efficient X3 ever, as it comes with automatic start/stop, which you can disable, and a configurable driving mode called Eco Pro, which dulls the throttle and limits climate control use to save fuel. On top of that, the four-cylinder makes the same 240 horsepower, but it is delivered 1600 rpm earlier (at 5000 rpm). Crucially, peak torque increases by 39 pound-feet, to 260, but also arrives much sooner, at 1250 rpm. While our best run to 60 mph in the six-cylinder X3 took 6.7 seconds, BMW estimates the N20 version will require just 6.5 seconds.
More fuel-efficient, more powerful, and faster -- what's the downside? Well, there's the $1400 cost increase for the base model that will be added to 2013 models, and that's about for objective complaints. Me? I miss all naturally aspirated engines and the rasp and revs that they're capable of. BMW's new, high-output turbo engines generate fantastic amounts of power, but that power falls off quickly, and the top end feel can feel soggy. No, I'm not asking for an X3 that revs to 9000 rpm, but I will miss the sound of the occasional redline pull when merging on a freeway onramp.
|Our Vehicle |
|Service life ||12 months/26,355 miles |
|Average fuel economy ||26.1 mpg |
|CO2 emissions ||0.90 lb/mi |
|Energy consumption ||156 kW-hr/100mi |
|Unresolved problems ||None |
|Maintenance cost ||$0 (1 x oil change, inspection) |
|Normal-wear cost ||$0 |