Stepping it up a notch, we went for devices with a practical use. First was the BMW Performance steering wheel. It has the same thick rim as the stock part and retains the multi-function buttons, but it's finished in black leather and alcantara. At the top of the rim are two LED strips that operate as programmable shift lights. There's also a central display with a number of timers including lap time, quarter mile, etc.
It even had a g-meter that measured braking, acceleration and turning force. Then there was a water and oil temp readout, and since all the information was taken from the car's CAN-BUS system, you knew it was perfectly accurate.
The same alcantara was used on the new aluminum shift lever and boot. These were the visual parts of the BMW Performance short shift system that used a modified gear selector mechanism to hasten gear changes. Again, the quality was superb, and it wasn't so short you risked missing gears.
Not many people seem to realize the 135i has some of the biggest brakes ever fitted by BMW. The six-piston calipers are incredibly powerful, and while you can buy the complete set-up from BMW Performance for a 128i, we used the optional, stock-sized drilled rotors on our 135i. These are again OE quality and performed faultlessly, providing stronger stopping thanks to a combination of better pad bite and consistent cooling.
Perhaps the only BMW Performance part that failed to live up to expectations was the stainless steel exhaust. The manufacturer quoted a 10hp increase but we failed to see this. However, it again fitted perfectly, since it was basically a stock 135i exhaust modified for performance. More importantly, it sounded like the dogs of hell when you got on it. At wide-open throttle, the car barked and swiveled heads, yet it would return to a sophisticated deep, rich tone under normal driving, and never droned.
We know many readers were disappointed we left the engine software upgrade until last. People were hoping we'd go big-turbo and aim for 1000hp, but it was never that kind of project... the car was borrowed and limits were set. What's more, BMW had embedded code within the 135i's ECU that would detect torque spikes and invalidate the warranty - not something we wanted to do with a car that would return to BMW HQ.
We were waiting for somebody to crack the codes, and finally GIAC unlocked the secrets. In fact, we covered the dyno runs last month (et 2/10) and found 41whp.
If you own a 135i or 335i (or 535i, X5 or Z4 for that matter), we highly recommend the GIAC software. It perfectly matches the car's personality, offering mild manners off boost and a huge surge when the two turbos spool. It didn't even seem to increase fuel consumption, nor was it lumpy or hesitant. Where the 135i was fast before, it simply became even faster.
We'd previously measured a 135i 0-60mph time in 4.9sec. These cars are seriously quick. But the software made it supercar quick. Turn-the-car-around-and-drive-that-road-again fast. It was a blast.
As the final indignity, we returned the poor girl to stock before returning it to BMW. Just a few scars from a lowered ride height remaining as the indication of its former life. We're going to miss the 135i. We still feel it's one of the best performance bargains on the street, better than the R32, far superior to the Infinity G35 or Nissan 350Z and possibly even better than the 335i - although that can be argued either way...
The 135i gave us 20 months of trouble-free motoring. It averaged a slightly disappointing 17mpg in the city and about 27 on the freeway. But it had the ability to surprise you every time you got behind the wheel. It was a comfortable companion that was ready for a canyon-carve whenever the mood grabbed you, yet it was subtle enough to escape unwanted attention. And for that reason, we'd recommend the 135i to anybody with a few dollars stuffed in their pocket who's shopping for a new or used tuner car.