Spencer’s GT3: Scoping New Territory

Competing in S3 in his E92 for years had proven to Spencer Kimball how far one could realistically go with a street car, and what sort of compromises going that far required.

The BMW’s forgiving front-engine characteristics eventually got boring, and Spencer started looking for a platform that might challenge him more as a driver. Especially since he’d acquired a lot of seat time in his dependable M3, he had the skillset to try and extract more from a less forgiving platform.

“I’d always wanted a GT3, but they were too expensive. The more realistic bet was something like a C8 Corvette, and I liked the idea of something with a warranty, so I had to consider that one seriously. Then my friend let me know about a 991.1 GT3 that was in my price range, and when I leaned it was still under warranty and had a recent engine replacement, I decided to take a closer look.”

Less Than a Gamble

The early 991.1 GT3s had a top end oiling issue affecting cam wear that claimed this car’s first engine, but the G6 version of the motor which replaced the original included a new oiling system. “It’s similar to a destroked GT3 RS engine, but revs out to 9,000 instead of 8,500 like the RS,” Spencer added.

“I wanted to get most of the Cup car’s handling without converting to a full Cup car setup,” he added.

This upgrade, coupled with an affordable extended warranty, gave Spencer the confidence to move into supercar territory. After selling a few toys, he scraped together the rest needed to buy his first P-car.

The balance of a rear-engine machine was something that caught him by surprise. “I expected it to understeer in the slower corners, but it understeered way more than I predicted,” he began.

Even with the handling flaws, its potential was clear. “My first weekend with it, on stock suspension, I did a 1:53 at Thunderhill East without really feeling too confident in the car.”

To not try and fulfill all the promise of something so capable out of the box would be a mistake, and so Spencer delved deep into finding the right set of modifications to bring out the best from the car. “Initially, I wanted to keep it simple. Shocks and springs, maybe rollbar and some harnesses, but it snowballed pretty quickly after I tried it on track.”

By adding a set of MCS three-ways with four times the front spring rate, Dundon camber plates, and a set of AP 5000R Pro front brakes, he’d given the car a chance to shine. However, the car was far more particular when it came to setup changes – a half-degree of camber would make over a half second’s difference in lap times – so Spencer got truly nerdy and began a series of in-depth conversations with the engineers at Throttle Therapy, a local racing team that fields cars in Porsche Carrera Cup North America.

The sweet spot for a car that sees occasional street use was 4mm of toe out, 10 degrees of castor, and -3.6 degrees of front camber. That aggressive alignment would make the best possible use of the 265-section BF Goodrich Supercar 3R tires at the front axle.

A large Verus wing at the rear adds to the car’s innate traction advantage.

At the rear, the advised setting for maximum stability on entry was 5mm of toe in and -3.1 degrees of camber. The resulting balance was neutral to understeery on exit, but totally manageable on entry and, almost as if it’s unavoidable, a little pushy mid-corner when driven right. Before he could get the car to behave in that way, though, he needed to adjust his approach – a recalibration that took real time and thought.

He’d been used to the benign breakaway of the M3, which was “more of a momentum car with power,” as he put it. “You can enter fast and scrub speed mid-corner, and a little (or a large) lift is not going to upset the car. As long as you’re cautious at the power-down phase, the M3 is extremely predictable and easy to manage.”

The Porsche just isn’t as forgiving. In fact, he spun it immediately after getting out of his M3 and trying the same thing. “It just won’t respond to the same inputs nicely. It’s more of a slow-in, fast-out-car; you need to be careful with the brake input. For instance, I’ll hit 139 miles per hour before braking for Turn 1 at Thunderhill East, and if the car isn’t totally straight before braking, the rear end starts to move pretty noticeably as the brakes are applied. The extra toe-in helps with stability, but even still, it’s much less forgiving if it’s driven sloppily.”

“The trick is finding out how to ensure you have enough front grip for the speed you’re trying,” he said.

Delicate Touch

Get the car properly prepared for braking, and the deceleration is remarkable. On Supercar 3R tires, the braking zones can be condensed in a way the BMW, even on Yoko A60 Medium slicks, just won’t allow. Rear-engine weight distribution helps spread the load evenly across all four corners when the brakes are applied.

In longer corners, like Thunderhill’s Turn 2, where the understeer is prominent, he has to tread carefully. “I need to lift to rotate in the middle of these corners, but I have to make sure to lift just the right amount. There’s a fine line you have to walk there, and it’s easy to upset the car if you’re a little clumsy with your inputs mid-corner.”

However, get the direction change done neatly and the traction advantage is easy to exploit. “I steer with the throttle so much more, and it’s way more manageable when putting the power down. Even if it starts to wheelspin a little, it still moves forward.”

Despite the small window between grip and slip, he hasn’t looped it since. “There’ve been a couple big saves, but it mostly understeers at the limit.”

Both the BMW and the Porsche weigh about the same at 3,150 pounds, and the Porsche makes another ~15 more than the BMW. Still that mild power advantage alone isn’t what makes the Porsche lap the same tracks on harder tires nearly two seconds faster than the BMW ever did. That traction advantage, coupled with its incredible stopping power, has to be appreciated.

This build, he believes, will not go quite as far as the previous one did. For now, he’s content leaving the full interior and just putting in laps. However, he’s a committed tinkerer and thinks there’s a chance he’ll install some of the parts from the Porsche Motorsport catalog to sharpen the front end. “I might add the arms, the lip, and the front flares from the Cup car and widen the front tires a little. Thankfully, there are a lot of Porsche Motorsports parts that are easy to install, and these parts aren’t that expensive - the Cup car arms are cheaper than the street arms!”

Moving away from the brand that’s served him well and into a new one known for its eye-watering service costs has not been, as it’s nice to hear, as bad as one would expect. Porsche ownership comes with plenty of perks, and, as Spencer’s shown us, the prices aren’t necessarily life-ending. It takes some courage and a hefty up-front payment to move into this new arena, but it seems it’s paid off.