Ed Susman's 718 Cayman: Proving the Four-Cylinder's Potential

Caymans are a common sight at Northern Californian tracks, but not many of them make over 400 lb-ft of torque. Though the six-cylinder variants have a grander sort of appeal, Ed Susman, a Subaru tuner with a penchant for turbocharged flat-fours, saw the potential in the new 718 chassis with the 2.5-liter engine.

Now, with a seriously wide footprint and suspension upgrades to match the gains in grunt, his turbo Cayman has been proven as a particularly quick car on both quick and slow circuits. Even better, there’s still so much potential with the platform which Ed, an obsessive tuner, aims to unlock.

Now that Ed has gotten intimate with this force-fed, four-cylinder midship, he’s been able to give this car a dash of the old 911 Turbo ferocity that makes it a very different car to drive. Unlike the atmospheric variant, this Cayman requires the driver treat the throttle with extra concern. Does one sacrifice a little mid-corner speed with so much power available? Possibly, but if there’s a delay in throttle application, the straightline advantage makes up for whatever difference there may be—and then some. 

The factory output—365 horsepower and 309 lb-ft at the flywheel—is nothing to sniff at. More importantly for low-speed tracks, it’s the way the motor just pulls from zip that changes its character so much. from that of the high-revving atmospheric versions. A flatter mid-range and a screaming crescendo isn’t what this motor offers, instead, it pulls like a sled dog from virtually everywhere in the rev range. Because it makes its peak torque figure from 1,900 to 5,500 rpm, it really doesn’t matter which gear is selected. It’s this ability to keep the car moving forward at about any speed is something else which cannot be savored with the old naturally-aspirated motor.

Not surprisingly, those figures were a little on the conservative side—just as Porsche is wont to do. After Ed got his hands on the motor, all it took was a downpipe, an E30 blend of ethanol, and a little tuning on the factory ECU to extract serious gains.

Of course, it wouldn’t be possible without Ed’s magic. The motor now makes 460 horsepower and 440 lb-ft at the rear wheels. Even wilder, the powerband has been broadened some; pulling harder from 3,000 rpm to 7,500. As crazy as it might sound, there’s still more mojo available—it’s just that the fuel system needs a little beefing up before it’s accessible.

Since the peak figure is available just shy of 2,000 rpm, it makes the delivery a little less than linear. Depending on the tires he’s using, he switches between two maps on the Cobb Accessport to soften the mid-range torque. If he’s using A052s or Supercar 3Rs, he gives it the full enchilada. If he’s on street tires, there needs to be a slight softening of the gradient of the mid-range ramp in order keep the rears from spinning everywhere.

Regardless of compound chosen, Ed had to throw a set of 305s on the rear if he wanted any traction in the second-gear hairpins. Thanks to Apex Wheels for giving him a set of 19X9 and 19X11” SM-10s, he was able to get the desired amount of rubber within the the factory bodywork without any rubbing or rolling. Somehow, they fit underneath the factory bodywork. 

More than mere meat, the secret to its inspiring traction lies in his clever throttle tuning. Now, there’s a more linear throttle position-to-output to make that horse-kick delivery a little more manageable.

With the car making serious horsepower with relatively little work, Ed now had a series of figures he could attract a whole new slice of clientele interested in making their Cayman dust GT3s on the freeway. His work had only really begun, though. To get the car to do what it’s supposed to do best, he had to improve footwork to complement the free-breathing motor. 

The list of upgrades is refreshingly short. With a set of camber plates; SPL control arms, camber arms, and toe links; and Ohlins Street/Track coilovers, he’s been able to make the car much, much more manageable. “Where it was nervous, it’s now neutral,” he declared. 

The footage below definitely conveys the violence of the turbo motor—even if the muffled soundtrack doesn’t. Ed has to tread carefully, otherwise the turbo motor simply monsters the driven wheels. Still, there’s a real playfulness to it all. Clearly, the turbocharged motor suits the Cayman, but it changes the emphasis from rolling mid-corner speed to getting the thing pointed and administering that power. While he might not be able to lean on it like he might in a similarly sorted atmospheric variant; it still looks predictable and playful. 

The car still has a lot of work ahead of it if Ed’s going to be satisfied. The front end simply doesn’t cooperate as he’d like, mostly in the high speed sections, and so he’s planned a bit of aero and weight reduction to help this car point as he’d like it to. For now, he’ll keep himself busy improving the deftness of his right foot—his brilliantly tuned engine is still grunty enough to roast the rears in fourth-gear corners.