After more than a year, our tenure with the BMW 335i Sport project car is about to end, but we couldn't let it fade into obscurity, deciding instead to send it out in a blaze of glory. Or so we hoped...

Having built it over the past 12 months or more, waiting for the latest parts to emerge from a rather reluctant aftermarket, we've grown to love its rigid chassis, excellent power delivery, luxurious interior and high-tech gadgets.

Apart from a bit more power, we really don't know why you'd choose a 5, 6 or 7 Series over the 335i. It has all the electronics of its more expensive siblings, including lane departure, blindspot and collision warnings, heads-up display plus the full suite of BMW Connected iDrive and infotainment features in a well proportioned package that regularly returns 26mpg for daily driving and will hit 60mph in about 5sec.

We're confident the F30 3 Series is still the best in its class and were looking for a fight to prove it. And that was when we came across the new Cadillac ATS.

Bringing the edgy styling of the larger CTS model into the compact market, along with some clever TV advertising and the hopes of a revived domestic manufacturer, the ATS caught our attention.

With a selection of four- and six-cylinder engines, RWD or AWD layouts, plus a big-screen infotainment center, it seemed to match our BMW in most areas. More importantly, its base price was $46695 for the 3.6L compared to $42090 for our 335i. Once you added all the bells and whistles, however, the Caddy would cost you $48190 and our fully loaded Bimmer was $49185 - close enough for our purposes. So could Cadillac really build a car to rival the 3 Series?

Since our 335i Sport was modified with a raft of top-notch aftermarket equipment, we needed an ATS that could also match it on that front: Step forward D3 Group.

D3 Cadillac

Having built SEMA show cars for several carmakers, the team at D3 Group had submitted a proposal to Cadillac for a twin-turbo Escalade back in 2003. It was rejected at the time because the company was considering it's own V-Series model, but some forward thinking individuals in Detroit approached D3 to see what could be done with the STS and CTS models.

The result was an instant success, with D3 breaking the brand's old fogey mold, giving the models a new twist. As the association blossomed, Cadillac has supplied more support, more vehicles and inside information to where D3 parts are now the only Officially Licensed Products (OLP) for the brand, available at all dealers nationwide.

The Licensed Product range for the ATS will eventually include a complete body kit unavailable for our photo shoot. However, D3 also creates its own range of parts that some dealers distribute or is available at d3cadillac.com

The D3 product line is a little more aggressive than the mainstream OLP parts and included the roof spoiler, rear wing, exhaust and coilovers on the ATS 3.6L we tested here.

The suspension is based on US-built JRI racing shocks that are converted to coilovers by D3. The stainless steel axle-back exhaust was a prototype unit that lacked the fit, finish and sound of the subsequent production piece, but was all D3 had available at the time since we're relatively early into their production process.

The car also had D3's Street Tune ECU software and a set of forged 18" TSW Interlagos wheels with Toyo T1S tires.

BMW M Performance

In the ideal world, while the Cadillac was fitted with parts from its official partner, our 335i Sport would be equipped from head-to-toe in dealer-fit parts from BMW M Performance. However, we'd decided to mix and match a few choice components to create a hybrid.

We've covered most of the parts in previous issues, and installed two new items that will be highlighted next month. So our car was tested with the official BMW M Performance Power Kit (engine software, air box, engine cover), big brake kit, carbon fiber mirrors and black kidney grilles. It also had Bilstein PSS10 coilovers, stainless steel Borla cat-back exhaust, 20" HRE wheels and Nitto Invo tires.

This is by no means the most aggressively tuned F30 335i out there, but it represents a California-legal car that shouldn't have any dealer warranty issues. It was also well matched to the D3 ATS.

Objective Testing

Our first stop was european auto source in Anaheim, CA - a location where several parts had earlier been fitted to our project BMW. We again utilized their dyno to assess the output of each car and found that the BMW had a sizable advantage.

On the rollers, the 335i put down 286hp and 302 lb-ft at the wheels, compared to 261hp and 299 lb-ft we'd previously measured in stock form. This proved that the M Performance Power Kit had done its job.

It's worth noting that BMW claims the car should develop 300hp and 300 lb-ft at the crank. However, the manufacturer is notoriously understated and high wheel numbers aren't unusual.

The ATS could only summon 260hp and 227 lb-ft on the dyno. This was surprising since, on paper, the Caddy should have the advantage. Indeed, the carmaker claims 321hp and 275 lb-ft at the crank. These peak numbers are developed at higher RPM than the BMW, requiring you to rev the 3.6L V6 engine harder to exploit the performance.

The next test would be carried out by our colleagues at MotorTrend. If you like this test, you can see what they thought of our two cars in a video, which is part of their Head 2 Head series on YouTube. MT borrowed the cars for the video while we gained performance figures in return (losing years of life from our tires and clutch in the process!).

On the test track, MT would record 0-60mph times of 5.1sec for the BMW and 5.2sec for the ATS. Over the quarter-mile, both cars were identical, with times of 13.8sec at 102mph. Similarly, braking from 60-0mph would be completed in about 111ft.

In a figure-8 test, the Cadillac would generate more lateral g, recording 0.75g to the BMW's 0.73g. Again, it's not a decisive difference and could be explained in part by the Caddy's race-oriented suspension and the difference in tire compounds. We would later discover the BMW's Bilsteins had been left on the softest settings for some reason, handicapping the car.

With all the numbers stored, we could head into the canyons to discover how the car felt in the high-speed turns and uneven surfaces.

Canyons

Almost any car can be made to perform well on a smooth racetrack, but the unforgiving environment of southern California's notorious canyon roads can make or break a reputation.

Since we're looking at every aspect, with a view to which would be the best to purchase as a tuner car and daily driver, let's start with the appearance.

Beauty is in the eye of the beholder, and both cars have their fans and detractors. And while neither are stunners in the purest sense, the BMW is more handsome, particularly when lowered on its 20" HRE C100 wheels that emphasize its taut fender lines and sweeping swage line, especially viewed from the rear.

The ATS is more angular, faithful to the Cadillac design language established by the CTS, although less extreme than the bigger sedan. In our eyes, it's better for it, looking more youthful: particularly from the front.

The rear is rather busy for our taste, not helped by the full-length third brake light, or prototype D3 mufflers. Admittedly, the latter will be more refined as a production version.

The upright head- and tail lights make the car look rather tall, where the BMW design emphasizes its width, making it seem lower and sleeker.

The 18" forged TSW Interlagos wheels were well suited to the Caddy, giving the right blend of sport and sophistication. And with its lowered suspension, the ATS was definitely turning a few heads. However, its smaller wheels and large body panels meant the TSWs were swallowed-up by the Cadillac, where the BMW's arches sit higher in the body, making the wheels more prominent.

Without its styling kit available, D3 had fitted its trunk and roof spoilers that undoubtedly made it more sporty, but did add to the complexity of the rear-end. Our 335i, on the other hand, was visually stock with the exception of BMW M Performance black kidney grilles and carbon mirrors - tiny details that made a significant difference.

The interiors reflected the exterior treatments, with the BMW's being rather minimalist and the Cadillac having extrovert design elements. As we've already stated, our 335i is loaded with the latest technology as well as supportive sports seats and a thick-rimmed steering wheel.

Cadillac appears to offer many of the same technologies as BMW, although our test car didn't have everything fitted. That said, the dash and console layout mirrored some exterior design elements and pushing buttons was accompanied by an unusual "thud" sound to confirm operation. There was also the widescreen CUE infotainment display that gave access to navigation, telephone, media, etc. The system employed touchscreen technology in preference to BMW's much-improved iDrive system. Using it, we can see why BMW engineers eschew this system because a moving car makes it hard to press the right spot on the screen, causing you to remove your eyes from the road for longer.

Overall, the Cadillac interior didn't adequately reflect the surprisingly sporty nature of the car itself, yet we were pleasantly surprised by the quality and technology in the Cadillac - its double-stitched leather dashboard a nice feature. However, we defer to the BMW for its greater refinement, although we concede we're very familiar with it after 12 months. So while we prefer the Bimmer, the Caddy wasn't far behind.

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