How to make a Porsche Boxster into a street-legal kart

Delete, Delete, Delete

With a rough idea of what he could do with the Boxster platform, Dennis made an offer of $1600. A short time later, the Porsche arrived at his house on a trailer.

A closer look revealed minimal frame damage. Even better, the only real mechanical issue turned out to be a damaged radiator. In fact, the car was so solid that Dennis almost scrapped his kart idea and briefly considered simply repairing it. 

After some cursory research online, though, he realized that the cost of OEM–or even aftermarket–replacement parts would quickly exceed his initial investment, which admittedly was not very much. “Upon inspecting the actual damage,” he says, “it turned out to be perfect for the kart conversion.”

The day after Thanksgiving in 2020, Dennis started stripping the Porsche’s body and chassis of anything that wasn’t essential to keeping it drivable–a process that took some research. “I investigated the frame structure of the 986 Boxster to determine how much could be removed,” he explains. “I also read several metal fabrication books and watched lots of videos on roll cage fabrication to learn how to properly design the roll cage as well as what materials to use.” 

He used 1.5-inch-diameter DOM steel tubing in 0.120-inch thickness for the roll cage. He admits that chromoly steel would have been a bit lighter, but it’s also four times the cost and is often TIG welded. He used 11- and 14-gauge flat steel for the brackets and reinforcing plates.

His tool collection, as expected, quickly grew, and soon his garage was populated by a welder, tubing bender, tubing roller, angle grinders, a Sawzall, a plasma cutter, a chop saw–and, well, you get the idea.

[10 Must-Have Tools for a Scratch-Built Car]

Caging the Beast

Wielding his arsenal of tools, Dennis enthusiastically added lightness. From the front bumper to the rear, every body panel of the Boxster was removed except the hood. 

Look, it’s practical, too. This lightweight Boxster kart can haul a bike.

The next step was slicing off unneeded sheet metal from the unibody. Even the rear upper strut mounts were removed, which meant fabricating new plates for the shocks to bolt to. To accomplish this while keeping the suspension geometry to its factory specifications, Dennis welded in the custom upper shock mounts, installed the dampers, and then continued removing any sheet metal that wasn’t critical.

While he was deleting bodywork, Dennis was building what amounts to an exoskeleton to keep the kart’s structure rigid enough to remain safe on the road. “One big challenge in adding a roll cage to a unibody car is that you have to weld in plates between the frame and tubing to dissipate potential crash forces,” he notes. “With this build, there were no large surfaces suitable for standard plates, so I created braces with additional plug welds and reinforced those in different axes to achieve the same effect.” 

Coming Alive

Once the roll cage was fabricated and welded together around the Porsche’s stripped-out unibody, Dennis delivered the car to a friend’s paint shop. He chose a color he found on a mountain bike, though it happens to look very much like the factory Porsche hue of Mexico Blue as well as Toyota’s Voodoo Blue. 

Boxster DNA shines through despite all the fabrication, as the dashboard and shift knob were sourced from the donor vehicle. The hood also came from a Boxster–it’s just been repositioned a bit. 

Now to add illumination. The removal of the bodywork meant there was no longer anywhere to mount the front and rear lights, so Dennis added some Hella headlights–DOT-approved components from a Polaris Slingshot. The headlight rings are modeled after those found on the Panamera and, like other modern Porsches, use four LEDs. The brake lights and taillights are universal and were originally intended for motorcycle and ATV applications. And the front grille mesh? Inspired by the Porsche 918.

All the wiring runs through the roll cage, so it’s hidden from view. Dennis relocated the ECU and rear relays to behind the passenger seat, where they’re also largely out of sight. He also moved the coolant reservoir and oil fill tube to allow room for the added bracing that spans and reinforces the rear shock towers. 

A set of adjustable coil-overs–a Bilstein PSS9 setup–was required to return the extensively lightened chassis to its lower stance. “I knew the car might sit too high and ride rough after removing so much weight,” he explains, “so I wanted the adjustability for ride height and compression rebound and damping.” The rest of the suspension remains stock. 

Seven months and an estimated 700 hours of work later, the remade Boxster hit the road again–lighter, faster, simplified.