First Test: 2011 BMW 335is

[ahmed_7erzon]

As we've been blathering on for weeks about the wonders of BMW's spanking-new 3.0-liter N55 engine (it traded one of its turbos for Valvetronic and came out ahead on responsiveness and fuel consumption while breaking even in horsepower and torque), the Roundel gang has been readying a sportier new 335is model powered by, what? The old twin-turbo? Tweaked to spool out an extra 20 horses and 32 pound-feet (make that, 70 extra pound-feet for short bursts of overboost!)? C'mon, guys. Admit what the Net has been alleging all along: the old twin-turbo really made gobs more power and torque than you let on, right?



Nein.

The engineers swear on a stack of product-change-notice paperwork that indeed this new version, nicknamed N54B30, is tweaked to pump more air for improved performance. The mission of this North America-only model is to cut the factory in on some of the action BMW owners have been giving companies like Dinan, Hartge, AC Schnitzer, et al. in search of a bit more performance and exclusivity. Indeed the added power is largely derived in the same way those guys often make it -- with a hotter chip that turns up the boost (from 8.7 psi in the 2009 335i to 11.6 psi nominal peak). As for the aforementioned overboost of up to 14.5 psi, this only happens for a maximum of seven seconds, generally below 4500 rpm, so the horsepower never tops 320. Unlike some of those other guys, however, BMW upgrades the cooling system substantially (an auxiliary radiator and an oil cooler flank the main radiator and the cooling fan's performance is increased), to preserve manufacturer-warranted durability.



Other powertrain changes include more rigid hydraulic engine mounts and a rortier exhaust note (it doesn't pass Euro sound regs but sounds terrific, though exhaust backpressure is unchanged). It's available with either the six-speed manual or the seven-speed twin-clutch automatic. You'll also find versions of this engine powering the new 740i (315 horsepower) and Z4 sDrive35is (335 horsepower, thanks to that car's roomier, cooler underhood environment).


Because 335i coupes come standard with the sedan's M Sport suspension anyway, there is virtually no change to the hardtop's chassis specifications, but the convertible is lowered 0.4 inch and its spring and damper rates are firmed up to coupe/M Sport specs. Coupes and convertibles get 335is-specific five-twin-spoke wheels as standard, with 19s optional.

Dressing up the exterior are sportier looking fascias and side skirts, with black-lacquer-look grille surrounds, mirror caps, and a matte black rear diffuser (which BMW engineers claim smoothes air separation at the rear, but this engineer is skeptical of that assertion). The front fascia includes foglamps for the convertible, but coupes will devote that space to ducting air to the extra heat-exchangers, as they're more likely to see track duty (our prototype test cars all show fogs in that spot, however).