2013 Ford Mustang Shelby GT500 vs 2013 Chevrolet Camaro ZL1: Dyno Tested

Decades of rivalry between Ford and Chevy have culminated into the quite-loony 2013 Chevrolet Camaro ZL1 and 2013 Ford Shelby GT500. They're the two biggest-gun pony cars ever turned loose by their respective manufacturers, collectively blowing clean past the 1000-horsepower threshold like it was wet tissue paper, amassing a grand total of 1,242 horsepower.

You already know that the GT500 is the stouter of the two, but have their manufacturers padded their numbers at all? And what about the shapes of their respective torque cuves? Plus, um, gurgly V8s are fun.

We aimed to learn the score, so we tested the 2013 GT500 and 2013 Camaro ZL1 on the same dyno on the same day by the same operator using the same methodology. Even if you don't give a whit about any of that, dyno testing allows us to capture all the snorts and sounds from these two leviathans, which alone is worth the visit. 

Elimination of variables produces the best results when it comes to dyno-testing. And with our same-times-four environment, we've eliminated the hell out of some variables. 

We'll focus on the ZL1 since we've already shared the GT500's dyno result. The ZL1 borrows the supercharged pushrod 6.2-liter "LSA" V8 from the Cadillac CTS-V and gains some 24 hp in the process thanks to revisions to the intake and exhaust. It's an engine architecture that debuted in 1997 as the LS1; variants went on to find homes in countless GM vehicles from trucks to the Corvette ZR1 and everything in between. Today, GM's got the LS architecture dialed.

In total the ZL1's factory ratings are 580 horsepower and 556 lb-ft of torque as measured at the flywheel. One would expect the 580-hp Camaro ZL1 to produce 82 fewer peak horsepower than the 662-hp Shelby GT500 when tested on an engine dyno.

When you factor in drivetrain loss, the gap between the two cars should shrink slightly. So in terms of chassis dyno results, really we'd expect the ZL1 to produce something closer to 75 fewer horsepower than the GT500.

Reality doesn't care about your freaking algebra. Here's what we found when we tested these cars on MD Automotive's Dynojet chassis dyno:

There's a lot going on here. First off, peak numbers for the ZL1 -- it kicked out a nice round 497 horsepower and 497 lb-ft at the wheels with that classic dome of a torque curve we've come to expect from this engine architecture. It was terrific on the dyno in terms of staving off heat, each run liberating a few more ponies than the last. Even a dozen runs in, the ZL1 exhibited no signs of power-sapping heat soak and just settled into a groove. It's a real-world, near-as-dammit 500 rwhp pony car right from the factory. You just can't help but be impressed.

Impressed, that is, until you see that the GT500 produced 105 lb-ft and 98 horsepower more power than the ZL1.

But back to the ZL1 for a moment. Around 3400 rpm the butterflies in its exhaust open, uncorking the LSA's sound signature in a big way. Then at 6200 the LSA V8 reaches an abrupt fuel cut, in stark contrast to the GT500's "soft" rev limiter.

To our ears the GT500 has the better-sounding engine. But such things are subjective, so we won't dwell on that except to reiterate that the GT500 has the better-sounding engine.

One factor in the larger-than-expected gap in peak power between the two cars pertains to that drivetrain loss -- the ZL1's independent rear suspension just might have more drivetrain loss than the GT500's live rear axle. See, the ZL1's power takes a more tortured path to the ground as it passes through the u-joints that support the two axles at each end.

This explanation assumes the transmissions, driveshafts, differentials and tires of the two cars exhibit similar loss characteristics. Your guess is as good as mine, unless you're a Ford or Chevy drivetrain engineer, in which case your guess is about a million times better than mine. 

Although the GT500 revs some 800 rpm higher, note that the GT500's power advantage does not come solely via revs -- at 6000 rpm where the ZL1 is generating its peak 497 rwhp, the GT500 churns out 575 rwhp. In fact, to match the ZL1's peak power, the GT500 requires just 4500 revs on the tach.

Clearly, the GT500 breathes more deeply than the ZL1 despite giving nearly a half-liter of displacement to the Camaro. Notable advantages for the Shelby include four-valve heads and a larger Eaton blower (the GT500 gets a TVS 2300; the ZL1 a TVS 1900).

But technical reasons are not at the root of GM's power deficiency (as if any ~500 rhwp car could ever be described as "power deficient") as the LS9 in the ZR1 proves there's additional potential lurking in the LS-series engine. And there's the rub. Nobody at GM would willingly allow any car in their stable to out-power the ZR1, their flagship sports car, so they're dealing with a pecking order situation. It's an artificial power cap that the GT500 simply does not have to contend with.

Sticky situation for GM, then. Still, there's that reality thing we talked about earlier, and laying right there is the gauntlet that Ford threw down, waiting to be picked up. It's your move, GM.