3.3 seconds.

When we paired this dynamic pony-car duo earlier this year, the performance gap between the newly refreshed 2018 Ford Mustang with Performance Package and the Camaro SS 1LE (a fourth-place finisher in our 2016 Best Driver's Car competition) was 3.3 seconds on our local Streets of Willow Springs handling circuit. The more powerful Mustang's best lap was an impressive 1:23.97, but the torquier Camaro's superior chassis delivered a blistering 1:20.67 lap, ranking it the sixth quickest production car on that circuit. As we noted, that yawning performance gap means these two cars probably wouldn't be allowed to compete in the same class.

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Not to worry. As that stinging defeat was announced, team Mustang was finalizing its next volley in this 50-years-long pony-car war: a chassis and aero package it simply calls Performance Pack 2, which is available only on fastback manual-transmission GTs (see graphic comparing GT, Perf Pack 1, and Perf Pack 2 equipment). As we outlined in an October First Look, this package was developed as a skunkworks passion project, developed by devoted Mustang team members who knew that the Perf Pack 1 wasn't fully exploiting the 2018 GT's ultimate performance potential. The twin keystones to unlocking this potential: a set of four 305/30ZR19 Michelin Pilot Sport Cup 2 tires exactly like those on the front of the GT350R, and an exacting retune of the Perf Pack 1's MagneRide shocks to keep those fat, near-racing-slick tires pressed to the ground.

The Tires

These barely DOT-legal semi-slicks feature two tread compounds, both of which are optimized for grip. The second one is located under the first, and it's designed to compensate for the difference in structural grip that occurs as the sculpted features of the top tread disappear, so that the tire's performance remains consistent throughout its (brief, 6/32-inch) tread life. These tires are lousy in the rain when new, becoming increasingly dangerous in the wet as their three tiny grooves disappear. By contrast, the Perf Pack 1's full-tread-depth Pilot Sport 4S tires feature three different compounds across five bands on the tire, a few of which are at least slightly concerned about wet traction and tire life (note that 4S does not stand for 4-Season).

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The Shocks

All 2018 Mustangs have monotube rear shocks, but only the MagneRide cars get inverted monotube front struts, as well. This more rigid design is enough stiffer under lateral cornering to require more robust wheel bearings. This in turn required unique knuckles, which permitted a relocation of the tie-rod mounts that reduces bump steer. All Mustangs with MagneRide enjoy these benefits. MagneRide's ultra-fast reaction time (sensing happens every millisecond; damping-rate changes typically take between 2 and 10 milliseconds) helps keep these wider and heavier front wheels and tires pressed to the ground. Another key difference in the MagneRide tuning for Perf Pack 2 is its greater control of transient roll. By monitoring four wheel-to-body sensors and the body's pitch and roll rates, the system predicts demand for lateral stiffness and tailors damping to minimize roll and smooth transitions during countersteering to prevent violent tank slappers. Vertical body motions are better controlled in Perf Pack 2, and Sport+ tuning serves as a useful rough-track damper setting.

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The Drive

Ford invited us to Monticello Motor Club, conveniently located about 90 minutes from New York City, to sample Perf Pack 2. Sadly, the one-day event coincided with a nasty weather pattern that felled thousands of trees in the area the night before our drive, many of which still littered our 12-mile winding public-road route. A generator provided electricity for our base camp at the track, and the rain held off just long enough for each journalist to get one session on the road course—two hot laps bracketed by recon and cool-down laps. Given this limited exposure, here's what we can say with reasonable certainty: The on-road ride in the Normal damper setting is slightly more civilized than that of a GT350, which is to say, it's way more comfortable than one might expect from a car with this one's extreme performance envelope. The front steamrollers tramline along worn pavement grooves a little, but far less than expected. On the track, the steering feel is superb, with absolutely linear chassis response, negligible body roll, and a reasonable sense of road-surface grip coming up through the wheel rim. This is thanks in part to Ford's wise decision not to fit a variable-ratio steering rack. The car feels plenty nimble without it, and the feel is so much more natural. It also seems safe to say that the disconnectedness Lieberman and Bovington noted between the Perf Pack 1 GT's front and rear suspension tuning has been exorcised along with that car's tendency to "roll over on itself." Beyond that, I'd love to tell you how grip levels ramped up as the new front splitter and rear spoiler pressed the car to the ground while exiting high-speed corners, but two warm-plus laps on an unfamiliar track with a few damp corners mean we'll have to save the definitive declarations for a better day on one of our favorite California desert tracks.

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Handicapping the Next Pony War Winner

So what's the over-under on this Perf Pack 2 vanquishing the SS 1LE in the next pony war grudge match? My money is on the Mustang coming close but not quite cleaning up, and there's no shame in this. In the last battle, we reported that the Perf Pack 1 car beat the Camaro in "cowboy science" categories: things like engine-note wonderfulness and the ability to win drag races longer than a quarter mile. This car clearly builds on all of that. But when I asked the team how much quicker the Perf Pack 2 was relative to the 1 around Streets of Willow Springs (they've tested the car at lots of tracks), the answer was "Between 2.5 and 3.0 seconds"—0.3 off the pace. Plus there's this: Close that gap the rest of the way, and the $44,590 GT really starts to threaten the $58,140 GT350's place in the pecking order. Can't have that.

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