2011 Buick Regal CXL Turbo and Regal CXL: Dyno Tested

You know it's a whole new kind of world when the newest Buicks are powered not by V8s or sixes, but exclusively by four-cylinders.

The 2011 Buick Regal brings two of 'em to the table -- a normally aspirated 2.4-liter and a 2.0-liter turbo. Give it a year and that figure goes to three, as a high-pressure version of the turbo will see duty in the 2012 Regal GS.

Buick hasn't yet finalized the horsepower and torque figures for these engines, so our curiosity got the best of us. We rounded up an example each of the base 2.4 and the force-fed 2-liter Regal in CXL trim and headed to MD Automotive's Dynojet chassis dyno in Westminster, CA. 

GM's preliminary numbers peg the normally aspirated engine at 182 horsepower at 6700 rpm and 172 lb-ft of torque at 4900 rpm. The boosted mill ups these figures to 220 hp at 5300 rpm and 258 lb-ft at 2000 rpm. Each is equipped with a 6-speed automatic transmission.

The figures above are as measured at the crankshaft. A chassis dyno measures the power that remains after it's been churned by the gearbox, beaten up by the halfshafts and finally smashed into the ground (or rollers, in this case) through the tires' squirmy tread blocks. Thus, chassis dyno numbers are always lower than those measured at the crank by about 10-15% for a FWD car as a very general rule.

Here's what we measured on the base Regal:

The non-turbo Regal has a fairly broad swath of torque, generating more than 140 lb-ft between 2500 and 5600 rpm, at which point the torque heads downward linearly until the 7000 soft rev limit. Considering its maximum torque is 153 lb-ft, this is defintely not a peaky engine. With 153 horsepower at the peak, it's not particularly overendowed either, but then, that's what the turbo engine is for.

Speaking of turbos...

In the turbocharged Regal, peak torque as measured at the wheels of 240 lb-ft hits at 3400 rpm, which compares favorably to GM's 258 lb-ft estimate at the flywheel. At this point in the rev range the turbo mill it is generating 91 pound feet more torque than the non-turbo. That's really the payoff of the turbo engine, as its torque rolls off precipitously once you wind it much past 4200 rpm.

It appears GM fitted a very small turbo to reap the quickest boost response possible. This comes at the expense of exhaust backpressure as the revs climb, which is why the torque falls so hard and why peak power is relatively low for a boosted 2-liter. We measured peak power of 177 hp at 4750 rpm, or about 25 hp more than the non-turbo's maximum power. These engines appear to be closer in peak power than the preliminary numbers suggest, which perhaps explains their preliminary-ness.

Then again, the best premium fuel in these parts is 91 octane, and it could be that the turbo engine ekes out a bit more sauce on the 93 and 94 octane you lucky devils get elsewhere in this great country.

In this overlay of the two cars' dyno results, you can see just how much the turbo giveth and then poopeth away -- there's a big ol' heap of additional midrange, and then at its 6200 rpm soft rev limit it's not really making any more power than the normally aspirated Regal.

Fortunately for enthusiasts, the Regal GS is on its way.