2012 Cadillac CTS-V Wagon: Dyno Tested

Is it even possible we've never dyno-tested the 2012 Cadillac CTS-V? Yeah, I can hardly believe it myself. The supercharged V8-powered wondersedan that couldn't be more American if it smacked an apple pie with a star-spangled baseball, that CTS-V?

And I regret to inform you that we still haven't. No, what we have here is the CTS-V's infinitely cooler twin brother - the 2012 Cadillac CTS-V Wagon.

You know all about this car already, but let's recap the CTS-V recipe. Take one 6.2-liter pushrod V8, add a dollop of liquid-to-air intercooling and bludgeon repeatedly with an Eaton TVS Roots blower until 556 horsepower and 551 lb-ft of torque come pouring out of the rear wheelwells. Best served as a shooting brake.

It's America's answer to the Mercedes-Benz E63 AMG Wagon, a car which is very likely the most versatile form of transportation in history. While we've yet to dyno an E63, we spent some time on the rollers with the CLS63 AMG, which is basically an E63 in a Halloween costume. 

The performance cred lurking under the hoods of the CTS-V Wagon and the CLS63 is surprisingly similar -- the CLS63's 5.5-liter V8 gives 0.7-liter to the Yank, but brings twin turbos, direct injection and twice as many valves to the table. All up, the CLS63 kicks out 550 horsepower and 590 lb-ft of torque when equipped with the optional AMG Development Package.

But let's not get ahead of ourselves. First, the CTS-V Wagon, as reported by our testing on MD Automotive's Dynojet chassis dyno:

Peak power of 492 horsepower arrives right at the 6200-rpm fuel cut, suggesting at first blush that there'd be more in this engine if it could just rev higher. Perhaps not a lot more, though, when you consider that the slope of the curve is approaching zero way out there.

It's got that dome of torque curve characteristic of GM's LS-series engines. Big torque is available at low revs, with more than 440 lb-ft on tap at 2350 rpm, peaking at 502 lb-ft. In a wagon. Can I get a 'hell yeah'? 

Naturally, these numbers are measured at the wheels.

The CTS-V appeared more sensitive to heat soak than the big Benz. After a few runs in the CTS-V, its output across the board showed signs of flagging, unlike the CLS63 which was surprisingly unfazed by heat.

Oh yeah, the Benz. Here's how the German powersled stacks up to Darth Vader's hearse, prior to heatsoak setting in:

The difference in peak torque we measured at the wheels -- 41 lb-ft -- correlates dead-smack on to the two cars' respective flywheel ratings. And, looking at peak power, the AMG squeaked out 22 hp more than the Cadillac despite nearly identical peak power ratings

But check out the area under each car's torque curve. Simply put, the Benz has a lot more of it. 

This is in part due to the choice of forced induction. Engines with Roots blowers -- like the CTS-V's LSA V8 -- have volumetric efficiency (VE) curves that mirror that of otherwise similar normally aspirated engines. In such engines, torque tracks closely with VE (though at higher revs internal engine friction starts to erode torque quicker than the VE drops off). 

With positive displacement blowers and no provision for driving the blower speed independently of the crankshaft speed, the shape of an Roots-blown engine's torque curve looks basically like that of an n/a engine. Only higher. Hence the torque dome.

Turbochargers, on the other hand, are not mechanically linked to the engine. Here, the mass flow delivered to the engine can be manipulated on the fly quite easily. This allows engineers to 'shape' the torque curve of turbocharged engines more finely, plumping up the output in those areas where the engine's volumetric efficiency rolls away. The torque curve, then, is more plateau than dome. There are a raft of other contributing factors, but this is a big one. In any case, turbos are partly why there's a lot of area under the CLS63's torque curve.

Considering the CLS63 costs a metric assload more than the CTS-V, I'd say the American contingent puts up a pretty solid fight in the grunt department.