From the April 1999 issue of Car and Driver.
Certainly, the new IRS lends real credence to the Cobra as a serious performance car, taming the old car’s occasional tail-happy tendencies, improving the ride (mainly by reducing pitching motions), and reducing the transmission of road noise into the cabin. It also looks cool on the stand.
The new IRS module provides the Cobra with a slightly wider track (by 1.2 inches), more suspension travel, and less lift under braking, which translates to less perceived dive at the front end. The IRS setup also provides a 125-pound reduction in unsprung weight, despite being 80 pounds heavier than the old live-axle suspension.
At least the increase in mass improves the car’s weight distribution and motivated SVT engineers to lighten the front end, where they trimmed 50 pounds. Of that, 20 pounds came off the engine, six from the adoption of a coil-on-plug direct ignition system. Whereas the previous car had a 57/43 fore-to-aft relationship, the Cobra now shows a 55/45 split. In the end, this test car was 110 pounds lighter than our last Cobra.
The engine gets a new tumble-port cylinder-head design that improves combustion efficiency and helps bump output to 320 hp at 6000 rpm and 317 pound-feet of torque at 4750. That’s an increase of 15 hp and 17 lb-ft over last year’s Cobra. Given its 7.5-percent power-to-weight advantage relative to our last identically geared Cobra, we expected to hit 60 mph in about five seconds flat, but 5.5 was the best we could do—0.1 second slower than the previous model. Top speed was also down, from 153 to just 149 mph in the slightly more aerodynamic car, all of which confirms that our low-mileage prototype test car wasn’t making a full head of steam.
Straight-line performance may have missed the target, but more important to sporty drivers is the feel of the Cobra on twisty pavement. The IRS makes the car feel more supple and thus more readable in corners. The rear end is less susceptible to bump steer than before, and as the geometry has been set up for a touch of toe-out as the car begins to heel over, then for toe-in (and safe understeer at the rear axle) at full lean, its off-center steering response is better, and its handling is more neutral at the limit. Hence, 0.03 g better skidpad performance at 0.88 g.
Even power-induced oversteer through Turn Three at Willow Springs raceway could be easily modulated at the throttle, allowing the driver’s right foot to control rotation through the corner. This kind of handling finesse was not available from the solid-axle car.
On smooth California pavement, it was hard to discern any comfort gained from the IRS based on our distant memory of the previous Cobra. Obviously, corrugated surfaces no longer produce the yaw found on solid-axle-equipped cars, and the new Cobra also handles two-wheel bumps with little tail hop.
The IRS seems to put the power down well, too, although it shudders a bit during full-power wheelspin starts of the kind needed to generate good acceleration times. Few owners will subject their cars to this treatment, and indeed, most will drive around with the standard-equipment full-range traction control switched on. This device (supplied by Bosch) detects wheel-speed disparities and intercedes by first retarding the ignition, then manipulating the fuel regime, cutting off cylinders to reduce torque. If the condition persists at speeds up to 62 mph, it will also apply a brake to direct torque to the other wheel.
The neat part about the Cobra’s traction control is that it has a so-called power-start feature that allows the driver to make wheelspin starts as long as both front wheels are spinning at the same rate. That’s how it knows the car is going straight-ahead. The rear axle incorporates a Traction-Loc limited-slip mechanism, and all Mustangs now run the same 3.27:1 final-drive ratio.
Naturally, the new Cobra inherits the slightly blocky styling of the 1999 Mustang, but it has is own unique features. The front fascia for one thing, and the Cobra R—like hood, for another. New forged alloy wheels are fitted, and they wear 245/45ZR-17 BFGoodrich Comp T/A tires that do a good job of keeping the Mustang on line, albeit with a fairly intrusive sound playback that starts at moderate cornering speeds as a low growl, then builds to a penetrating howl at the limit.
The engine pulls well, particularly from 3000 rpm up to its power peak at 6000 rpm, but there isn’t a rush to the redline like there is with GM’s LS1 motor, and revving the Ford V-8 beyond 6500 isn’t very productive. However, keep the Ford mill in its sweet band, and you’re rewarded with good power and one of the least inhibited exhaust notes in the business.
That power goes to ground via a new 11-inch clutch and a T45 five-speed box (now made by Tremec under license from Borg-Warner). The T45 gets the job done, but it isn’t the smoothest, most precise cog swapper around. In fact, at Willow Springs, where you rush out of a downhill left-hander in second gear into a right sweep onto the back straight, it takes real concentration to keep the car pointed and find third gear.
It’s fair to say that none of the other shifts is slick and natural-feeling, either. The best one can say is that selections are mechanically positive. But in every other way the Cobra manifests considerable refinement. The car’s structure may have retained seat, shifter, wheel, and pedal positions for enough years to accentuate their inconvenience for extremely tall drivers (for whom the seat does not track back enough and for whom the control relationships are never optimal), but it has received enough reinforcement and tuning tweaks to provide civilized levels of noise, vibration, and harshness, even at the new performance level.
Who said there’s no gain without pain?
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Source: Reviews - aranddriver.com
