A new dyno test shows the the tuning potential of the new N20 engine found in the also new 2012 BMW 328i. The folks at Automobile Magazine took the 328i onto a DynoJet dynamometer and showed that the N20 engine comes underrated from the factory.

Official numbers says that the 2.0 liter turbocharged four-cylinder unit outputs 240 horsepower and 260 lb-ft of torque, but the dyno test shows 222 hp and 245 lb-ft of torque at the wheels. The test also shows that the N20 makes a plateau of torque across the low and middle rpm ranges, and then it tapers off as the turbo’s airflow capacity nears.

The magazine says that BMW most likely has not underrated this engine, but rather uses the “Worst case scenario” power numbers, a situation that can happen during hot weather conditions.

Interesting enough is the fact that the chart shows the N20 outputting 92.5% of peak horsepower to the wheels, a figure close to the the N54 and N55 six-cylinders turbocharged units.

In a previous test, Automobile found the N52 3.0 liter straight six engine to output 231 hp at the wheels, a merely 9 ponies more than the N20. The peak torque was rated at 211 lb-ft for the N52, while the N20 “scored” 245 lb-ft of torque.

Our own Road Test Editor Shawn Molnar spent some time behind the new 328i and shared us his impressions:

“Now full-throttle, building speed, the true magic of BMW’s turbo 4 can be felt. I’ve said it before and I’ll say it again: BMW’s new N20 4 cylinder unit is fantastic. It differs from a typical 4 cylinder in that it loves to be revved. Most 4 bangers suffer from vibrational issues, so they sound and feel like they will grenade if you push the tachometer much beyond the half-way point. However, BMW is known foremost for their engines, and by optimizing friction and adding two balancing shafts, the N20 displays exemplary levels of vibration and harshness – that is to say, it doesn’t display vibration or harshness much at all. While driving the car, you would be hard-pressed to determine there is a 4 cylinder propelling you down the road. At startup the idle can be slightly rough, that was the only instance that made me think, “4 cylinder.”

Read our 2012 BMW 328i test drive