Options are what keep tuning enthusiasts hunting for the right car to modify and the best performance parts to install. This certainly holds true in our seemingly never-ending quest to upgrade our Project BMW 335i (F30). And sadly this represents the last installment in our 335i series since the car has now been returned to stock.

In previous issues we installed H&R coilovers and conducted a direct comparison with the KW parts, but we were recently contacted by Bilstein - a company with enviable track success. They provide the motorsport suspension components for one of the hottest GT chassis in racing: the Audi R8 LMS. Harnessing some of that technology, the new B16-PSS10 coilover suspension is said to deliver unrivalled handling and ride quality.

Offering 30-50mm (1.2-2") of lowering ability, along with ten-stage precision compression and rebound settings, you'd be hard pressed to find a kit more competitive. And as one of the last to come to market for the F30 chassis, it should also be one of the most extensively developed...

We had our good friends at GSR Autosport perform the installation and dial-in our new suspension. If you saw EC 12/13, you'll know they had to complete the task quickly in order to be ready for our BMW 335i Sport vs Cadillac ATS 3.6L comparison test, which we also shared with our big brother, Motor Trend.

At this point, we should point out we were very happy with the H&R components on the car. They offered a sporty ride with great comfort and sat the car really low without rubbing. It was a great combination but we were itching to sample an alternative.

Bilstein

Fitting the front struts was fairly straightforward: first we measured to see where the ride height was set before removing the H&R coilover kit. This would make life easier when setting the ride height since we really liked how the 335i sat, and knew we didn't encounter any rubbing problems at that height with this wheel and tire combination.

To start the fitting, first release the bottom of the strut from the pinch bolt in the hub. Then undo the sway bar end-link and unbolt the top mount. Our car doesn't have the complication of Electronic Damper Control (EDC), which made it easier to disassemble.

On the rear, the dampers unbolt from the top and bottom mounts, allowing the wishbone to droop, which gives you access to the coil spring for removal.

Once removed, the Bilstein spring perch slots onto the top of the new coil spring, allowing height adjustment when installed.

The GSR crew had everything bolted into the car in about an hour, even with us slowing them down for photos. There are installation instructions available online at bilsteinus.com on the online catalog pages.

When it came to setting the new ride height, dialing-in the new suspension to the previous measurements would turn out to be rather difficult. It appears Bilstein is less willing to give you as much height adjustment, opting for performance across a narrower drop zone.

After winding down the spring perches to their lowest setting, we came close to our original H&R ride height, but were approximately 0.25" higher all round.

Despite the small difference, the race-inspired stance was ready to take on the canyons and subsequently eliminate any doubts that the Cadillac could dethrone the king of the sport compact sedans.

As you'll read in the test, the ride is poised, albeit slightly soft after the dampers were initially dialed to their softest setting. Normally, we'd set them in the middle and adjust as necessary. Once resolved, the ride comfort remained perfectly acceptable, with slightly better bump absorption than either H&R or KW. It also seems to damp out high-speed undulations better and offered great body control.

Although we're running very low profile 20" tires, there was plenty of compliance in the suspension, which didn't crash into potholes, or bounce over freeway joints. With more practical 18 or 19" wheels, you'd have a great deal of comfort, while retaining the exemplary body control. It's firm without being stiff, tight without causing discomfort.

Borla

It took far too long for the aftermarket to respond to the F30 chassis, but it's eventually received the love it deserves. So our final upgrade would be a new performance exhaust system to replace the axle-back muffler supplied by BMW M Performance.

Although this was the official factory upgrade that wouldn't affect the dealer warranty, it was no louder than stock and didn't add any power. Therefore, we decided to sample a new stainless steel cat-back system from Borla to see if it would offer any improvement.

Once again, the task was entrusted to the team at european auto source (EAS), which would perform the installation and provide dyno results.

Fitting

The outgoing BMW M Performance exhaust was easy to remove, since it simply unclamps and is removed from its hangers. However, the Borla system was more extensive, so we decided to remove the entire OEM exhaust to reduce the installation time. Once the catalytic converter was disconnected, each hanger was slipped off its rubber mount. At this point, be sure the pipes are supported as they're removed.

The removal could be performed on jack stands if you're willing to wiggle under the car, but a lift obviously makes things considerably easier.

Once removed, we mocked up the Borla system on the ground to ensure we had everything needed - instructions were provided in case there was any confusion.

First, the stock catalytic converter (section 1) was bolted back into place, followed by the Borla mid-pipes (section 2), the X-pipe (section 3) and finally the muffler with polished tailpipes.

The Borla system comes with all the necessary clamps and, thanks to the flared pipe ends, slotting each piece into place required minimum effort.

Once bolted up and fitted to the hangers, we headed to the dyno. We really wanted to hear what difference had been made and compare it to our previous stock power curve to see if the new Borla exhaust system had contributed any gains.

Dyno

First off, let us assure you the Borla exhaust sounds superb. After the anti-climax of the BMW M Performance system, the Borla pipes sing. In fact, they got better with age, offering a deeper tone at idle, a hollow sound under load and a restrained bellow at high RPM. We're very happy to report it doesn't drone or resonate inside the cabin, making it as relaxing to drive the car as before. Only now you can enjoy your right-foot action a little more.

With our noise issues abated, we were still curious about power gains and again there was good news. While we've come to expect that anything behind the cat won't really make much numerical difference, we did see a slight increase. To be honest, the tests were done several weeks apart, so there could be some climatic influences, but the EAS dyno showed an improvement of 2-3hp from 4700-6200rpm. This was also reflected in the torque curve. Admittedly, this isn't something you'd necessarily feel, but driving a car with a better exhaust note certainly adds a feel good factor.

So that's the end of our Project BMW 335i. The car is already stripped and returned, to be auctioned to some lucky owner who won't be expecting the extra horsepower from the BMW M Performance Power Kit we left in place!

Supplier Part Price
GSR Autosport Bilstein PSS10 Coilovers $2462
european auto source Borla cat-back exhaust $1375

SOURCE
GSR Autosport
22482 Muirlands Blvd
Suite B
Lake Forest
CA  92630
949-333-0841
949-859-1535
www.gsrautosport.com
Borla
701 Arcturus Avenue
Oxnard
CA  93033
805-986-8600
www.borla.com
Bilstein
14102 Stowe Drive
Poway
CA  92064
858-386-5900
www.bilsteinus.com
BMW M Performance
www.shopbmwusa.com
European Auto Source
4015 E. Leaverton Court
Anaheim
CA  92807
866-669-0705
www.europeanautosource.com
By Ezekiel Wheeler
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