BMW 335i Performance Upgrades - Borla Exhaust - European Car Magazine

On paper, BMW's N54 turbo inline six was a tuner's dream. Direct injection, front-mounted intercooler and twin turbos, all attached to BMW's legendary drive dynamics. Most figured a simple software upgrade would make big power for very little cost. But it quickly became clear it was going to take considerable time and resources to penetrate the Siemens DME's defenses in order to manipulate the MSD80/81 code. This left some to develop external piggyback devices, but these simply acted as blinders, tricking the computer into thinking it's doing one thing when it's really doing something else. Now, GIAC has released its Stage 1 flash, and we just had to test it.

Vehicle Data

Engine: 3.0-liter I6, turbocharged and intercooled
Transmission: Six-speed automatic
Mileage: 44,908
Current modifications: Miro CSL Replica wheels, 8.5x19 (f), 9.5x19 (r)
Dyno Data Mustang MD-AWD-500 in 2wd Mode
Ambient temp: 80°F -86°F
Test gear: Fourth
Test octane: 91

Baseline

Peak power:
265 hp @ 5550 rpm
Peak torque:
284 lb-ft @ 3175 rpm
Temperature: 80° F
Humidity: 24%

Test Notes
The baseline and all subsequent testing were performed on the same day, utilizing the same tank of 91 octane fuel. All quoted horsepower and torque numbers are measured at the wheels. It's also important to keep in mind that the properly calibrated "Mustang" dyno produces more accurate real world horsepower and torque numbers. While these numbers might seem low when compared to figures gathered from a Dynojet, what's important is the differences between each dyno run. Those differences are what we use to validate the manufacturer's horsepower and torque claims.

Test 1

Performance
Peak power: 313 hp @ 5,500 rpm
Peak torque: 331 lb-ft @ 3,175 rpm
Max power gain: 60 hp @ 6175 rpm
Max torque gain: 63 lb-ft @ 4250 rpm

Installation time: 45 minutes
MSRP: $800

Pros
• OBD port flashing allows the ECU and harness completely unmolested
• Increased throttle response and smoother power transitions
• Increase rev limiter to 7200 rpm
• Speed limiter is removed in the DME
software (not by altering vehicle speed sensor data) leaving ABS and DSC functions unaffected
• DME receives accurate data from the engine sensors, giving the ability to be more proactive instead of reactive, allowing DME to deliver the proper amount of fuel, cam and engine timing based on real world conditions
• 100% reversible

Cons
• GIAC flashloader technology not available yet

Test Notes
Even though this '07 had been to the dealership on more than a dozen occasions it had never had any software updates done, even when they replaced the fuel pump. So instead of the spending the standard amount of time to flash the vehicle, it took an additional two hours to update the necessary systems to accept the later software version. We upgraded to the later software because BMW had made several beneficial improvements to overall drivability, making a better software base for Stage 1 recalibration.

The boost data was generated using a boost line attached directly to intake manifold then attached to an externally mounted 3bar GM style MAP sensor with a 0-5 volt analog output range that sends a signal that was then converted by the dyno Powerdyne software.

Test 2

Performance
Peak power: 311 hp @ 5950 rpm
Peak torque: 330 lb-ft @ 3125 rpm

Parts: X-pipe, right and left axle pipe, muffler assembly with 3.5-inch round tips, 2.38-inch and 2.50-inch muffler clamps, vacuum plug
Tools: T50 torx bit, 15, 18 mm and 5/16-inch socket, extension, ratchet, WD-40, tape measure, reciprocating saw or pipe cutter
Installation time: 1-1.5 hours
MSRP:$1,301.99

Pros
• 2.5-inch fully mandrel bent stainless steel tubing
• 21-pound weight savings over the stock system
• Merge X-Pipe is designed to create a vacuum between the right and left exhaust pipes, increasing exhaust gas velocity
• Merge X-pipe designed to deepen sound while reducing droning
• Borla Million-Mile Warranty offers replacement parts if the product has any defects in materials and workmanship for 1,000,000 miles

Cons
• Cutting of the stock system (not a Borla design problem) since factory system is one piece from the downpipes back and includes two catalytic converters; the only way to legally swap out the cat-back portion is to cut it
• Slip-joint construction makes installation a bit tricky
• Lack of sealing compound for slip-joints made eliminating small exhaust leaks difficult, requiring several adjustments

Test Notes
We let the exhaust cool for a while before we swapped it out, and by the time we returned to the dyno room and recalibrated the dyno, the outside temperature had increased to more than 100° Fahrenheit, and the dyno room had had increased to 86°.

Conclusion
We feel this is the way the vehicle should have come from the factory. That said, the first thing you notice is that the GIAC Stage 1 has somehow "unconfused" the 335i. The difference is immediately apparent from behind the wheel. From tip-in to full throttle, the power delivery is smooth and lag-free. Unlike some tuned turbo cars where the accelerator positions are over exaggerated (i.e., quarter throttle gives you full boost while three-quarters gives you nothing) the 335i's power delivery based on pedal position is very balanced, giving full control of the powerband.

A perfect example of how the Stage 1 software lets the DME know what's really going is especially clear if you're drivingan automatic. With piggyback modules the automatic transmission would over time begin to shift harshly, inconsistently, and somehow seemed confused about what to do. This makes sense, considering that the transmission relies on load and speed data from the DME to operate. With GIAC software installed the automatic was transformed, more predictable, and gear-to-gear transitions were quick and smooth (no clunky shifts).

From a standstill, with the tranny in S mode and the accelerator inducing full throttle, I was amazed how quickly the car reacted and pulled all the way to redline. It behaved more like it had a V8 than a turbo six. A quick run through the canyon gave me another surprise: the vehicle's ability to sustain power whether I was on flat ground, powering out of a corner, or going up hills-again pulling all the way to redline.

We didn't expect power gains from the Borla exhaust, ultimately because it doesn't take care of the second set of catalytic converters, a major restriction in the factory exhaust. Borla does offer a set of race pipes that eliminates the secondaries (for off-road use only); we'll be testing these at a later date when GIAC's Stage 2 software becomes available. The exhaust did give a tasteful baritone resonance without becoming overly "boomy," which can be a frequent problem with automatic transmissions.

PARTS COST GIAC STAGE 1 SOFTWARE     $800 BORLA CAT-BACK EXHAUST   $1,301.99 MSRP TOTAL. $2,101.99

A quick note...
...for those concerned about their dealer uncovering software modification. This exact 335i has been to a couple different dealerships more than a half dozen times. As we noted earlier, it even had its fuel pump replaced. The dealers never once reprogrammed the DME or any other of the 18 systems that required updates.

Following the install, I stopped by a local BMW dealer to see a friend and why this vehicle had never been updated. He informed me that the updates take a long time to perform, they tie up the equipment, and they don't really get paid much to do it, so unless it's absolutely necessary, they don't bother.

While I was there I asked him to call out one of his greenest techs to see if he could tell whether the DME had been physically accessed. Within a minute he was able to point out a couple things that might indicate someone had tried to remove the cowling, and he was correct since the 335i did have a piggyback unit installed at one point. By then it had been removed, but traces from the installation and removal process were evident. Before I let him go I asked him if he routinely looked for this type of stuff. He replied: "I wouldn't look for it. I would only notice it if I happened to come across it during a repair or service." No matter what you choose to do with your own vehicle, keep in mind that if you play with the system, you must be prepared to deal with the consequences.

Having put a few thousand miles on various piggyback devices, I'm very familiar with them and I can honestly say that I've never had any issues. Then again, I never felt completely comfortable with the way they work. I think it's important when you tune a vehicle that every aspect of the software is recalibrated to accommodate the increases in power and torque, because power affects each system differently. Stay tuned for our Stage 2 testing as soon as the software becomes available.-AG