Flat is a word that keeps coming up as the vehicle dynamics engineer at the helm of the 2015 Ford Mustang EcoBoost describes the results of his work fettling on this pending pony’s new suspenders. It corners flatter, it brakes a lot flatter, and it’s just a much more buttoned down car -- at least to hear him tell it. We’re in the sprawling parking lot outside the zMAX Dragway, across the street from Charlotte Motor Speedway threading the cones of a moderate-speed autocross course. Indeed, the view and sensations coming through the right chair give little cause for argument, and there’s plenty of good reason to expect such results based on the engineering design.

This 2015 Mustang, the first that any journalists have gotten a ride in yet, is (almost) the nimblest package that will be offered -- 305-plus-horses from the 2.3-liter turbo and the performance package, but the six-speed paddle-shifted automatic is probably not the nimblest transmission. It’s a good choice for this exercise, though, as I can sense the way the shift schedule changes as my chauffeur toggles between the normal/sport/track modes better than I could have perceived clutch takeup and shifter feel without using my own limbs. 2015 Ford Mustang Ecoboost Rear Side View That track package eliminates all rubber from the front suspension links responsible for transmitting lateral forces from the tires to the chassis, replacing them with metal-to-metal ball joints. The suspension cradle to which they are attached is also un-isolated, all of which makes for more immediate reactions to steering inputs, and (theoretically) more feedback through the adjustable electric-assist steering (it’s supplied by the same folks who made the Boss 302’s rack). There’s more magic in the suspension geometry, made possible in part by the front struts’ double ball-joint lower attachment. This produces a “virtual” steering axis in the form of a cone that has the effect of moving the effective steering axis point further outboard, increasing road feel.

Whether jinking through a lane-change or slalom event or accelerating through a broader sweeper, the 2015 Mustang EcoBoost’s body does seem to maintain a reasonably even keel -- a sensation backed up by watching laps from trackside. Overall grip from the 255/40R-19 Pirelli P Zero summer tires also felt appropriately sporting, and the limits we approached produced minimal squeal.

2015 Ford Mustang Ecoboost Front Side View Yellow 2015 Ford Mustang Ecoboost Turning 2015 Ford Mustang Ecoboost Front Side View To The Right 2015 Ford Mustang Ecoboost Door Open 2015 Ford Mustang Ecoboost Side View Door Open 2015 Ford Mustang Ecoboost Front Side View Yellow Door Open That double-ball-joint setup also frees up space for big brakes without increasing wheel offset. Performance package brakes here measure 13.9-inches in front, clamped by four-piston fixed calipers (just about like on the 2014 Mustang GT Track or Brembo Brake packages). Rears are 13.0-inch vented in the rear. The independent “integral-link” rear suspension permits way more anti-dive geometry than anyone’s live axle could, which is the biggest contributor to the flatter braking. Working together, the front and rear suspension resist dive, squat, and lift twice as well as before.

One burning question that goes unanswered for yet another 2015 Mustang program is mass. The only clue we got was an admonition against counting on the I-4 weighing a whole lot less than the base aluminum V-6. It will, however, reach peak torque way lower in the rev range, meaning that even if it doesn’t produce much more than the 305 hp that the V-6 does, it should very easily outrun that car. It certainly seemed to move out every bit as smartly as a 2014 Mustang V-6, thanks in some part to the performance package’s 3.55:1 axle ratio. That axle is optional on the 2015 Mustang V-6 and 2015 Mustang EcoBoost I-4, with 3.15:1 the base axle on both (the 2014 V-6 made do with 2.73:1 or 3.31:1, the latter of which will also be offered on the 2015 I-4). Folks interested in optimizing their EcoBoost Mustangs for autocross circuits like this (and not CAFE optimization) might try fitting a 3.73:1 axle, which we’re told will be offered on the V-8, though it doesn’t show up on the spec sheets yet. In the “track” transmission mode, lower gears seemed to hold nicely while braking into the big sweeper, and the box’s reaction to paddle inputs seemed quite instantaneous. In that mode, a manual gear selection pretty much holds no matter what, resting on a smooth rev limiter if you insist. 2015 Ford Mustang Ecoboost Front Side View The engine note of the 2015 Mustang EcoBoost sounded pleasingly snarly -- which isn’t easy with a turbo muffling the exhaust -- though final sound tuning has yet to be completed. When it is, the sound reaching your ears will be a symphonic composition of genuine intake and exhaust frequencies enhanced by nice noises piped in through a sound pipe and objectionable ones erased via active noise cancelation. That’s about all we can tell you at this point, but rest assured the Chinese water-torture dribbled release of Pony-car info will continue right on through the promised full-on drive programs later this year.

Riding Notes

• Ford is continuously polishing its final product. The Mustang we rode in was a prototype, still in need of some final tweaks. Its interior was mostly complete, but many of the surfaces were lacking texture or constructed with the incorrect material – standard prototype fare.
• A manual and a traditional automatic transmission will be offered at launch, with both containing six gears. While the standard trans is a carryover, the automatic has been upgraded with paddle shifters and is driver configurable with four different electronic modes (Normal, Sport, Track and Snow/Wet) that alter shift points, traction control and throttle response. Our test car was equipped with the automatic.
• The steering effort may also be adjusted between three different settings (Comfort, Normal and Sport), thanks to its new electrically assisted rack.
• Our car was optioned with a Performance Package that will be a must-have for enthusiasts. It includes firmer dampers and higher-rate springs (take a closer look and note that the 2015 model already rides a bit lower, with tighter wheel well gaps), chassis bracing, upgraded front bushings and stiffer sway bars (by about five percent). More capable four-piston brake calipers are fitted to the front axle over 13.8-inch ventilated rotors, while the rear brakes retain a single-piston sliding caliper over 13.0-inch ventilated discs. The package does nothing for the engine, but a new 3.55 rear axle ratio (replacing a 3.31) will make it feel a bit quicker. Lastly, a set of 19-inch alloys wrapped in performance-oriented Pirelli PZero rubber (255/40R19 at all four corners) improves grip.
• Off-the-line acceleration wasn't tire-chirpingly quick, even in the sportiest setting, but once the engine was under full boost – we noted a bit more than 15 psi on the analog dial between the center HVAC vents – it started to pull strongly, wanting to stretch its legs. (Ambient temperatures were in the mid-90s, with equally high humidity, both of which work against a turbocharged powerplant.) The short autocross course limited the driver to just second gear, with the shift from first to second arriving smoothly. Our pilot demonstrated shifting in both automatic and manual modes, which features nifty rev-matching throttle-blips, and it never felt sharp, harsh or tiringly aggressive.
• As is nearly always the case with a four-cylinder engine, the new 2.3-liter lacks the ultimate smoothness of a six or eight. At this stage of tune, however, it's no better or worse than the racket emanating from BMW's new four. There was a notable intake and exhaust note, both pleasantly tuned, but we couldn't catch any turbo whine in our short jaunt (Ford didn't allow us to pry open the hood and view the intake design). This Mustang's siblings will each have much better lungs, while the four will require some acclimating.
• One big advantage a four-cylinder holds over a six- or eight-cylinder is reduced mass. During the parking lot autocross, the new Mustang felt impressively agile and light. There was very little body roll, even during extreme maneuvering (the car in this picture is cornering aggressively). Under heaving braking, the new chassis and sporty underpinnings – independent rear suspension and all – seemed to successfully resist the urge to dive or become unsettled. There was a bit of front-end push in the tightest sections, but applying the throttle quickly moved the weight rearward, extinguishing the understeer (the front of the coupe felt lighter than the rear, which would indicate good balance). We'd be willing to bet that the four will be the most nimble in the family.
• It's likely that Ford sees even more potential in the idea of an EcoBoost Mustang – new spy shots and video revealed earlier today suggests that the company may be working on a model with even higher performance, though its cylinder count remains unclear.