JOE JUSTICE DOES NOT GIVE HIGH FIVES. HE PLANS THEM. Estimates jumping trajectory, calculates arm speed, triangulates a meeting point. For him the high five is a physical manifestation of exuberance multiplied by the sum of satisfaction and happiness. And right now, in late September, as the 32-year-old Lynnwood resident stands outside of a four-stall garage next to his home, dressed in paint-spattered Carhartt cover-alls, he’s very happy. And satisfied and exuberant, no doubt because he just spent the last 90 minutes explaining how—if his numbers are correct—his automotive startup, Wikispeed, will change the car industry and manufacturing in general. So naturally he wants to high-five.

It’s difficult to not get caught up in Justice’s enthusiasm. In May 2010, Wikispeed was one of 27 finalists for the Progressive Insurance Automotive X Prize, a $10 million bounty offered to the three teams that designed mass-producible cars capable of getting 100 miles per gallon. Then in January 2011, Justice went to Detroit to exhibit his prototype, the SGT01, at the North American International Auto Show, the biggest car confab in the world, “the place where Ford unveils its new F150 each year,” he says. And this January, he’ll deliver his first two cars to paying customers.

Rattling off those accomplishments has amped him up, so here comes the high five. “We’re going to jump,” Justice says to me, taking note of his roughly two-inch height advantage, and then presumably plugging numbers into a hastily drawn-up formula in his head. He jabs a finger at a spot about two feet above us. “There. That’s what we’re aiming for, okay?” He bends at the knees and gets ready to leap, then hesitates, straightening up to point to the target again. “Right there. Got it?”

I guess.

“Ready, set, go.” We jump and…the heel of my hand awkwardly bumps his wrist, most likely because his formula incorrectly assumed that my excitement would equal his. (Which isn’t to say that I lacked enthusiasm; it’s just that he was practically springing out of his coveralls.) “That’s okay,” he says. “Let’s go again.” He recalculates. We jump, this time more or less in unison, and our palms meet more or less where he predicted they would.

“Yeah!” he cheers. He smiles, a toothy, open-mouthed, full-on-giddy smile. “Awesome.”

AWESOME POPS UP OFTEN IN CONVERSATIONS with Justice. “You can call me on my cell, which would be awesome,” he wrote in one email. “It is awesome working with you,” he wrote in another. The more than 100 volunteer engineers and mechanics who have joined the Wikispeed team—including Justice’s mother, his five siblings, and a cousin and uncle—are awesome. His response when I pointed out his affinity for the word? “That’s completely awesome.”

There are a couple reasons for Justice’s relentless optimism. First of all, he may actually be onto something with this car thing. Part of what makes the SGT01 so fuel efficient is its weight. The body is made of carbon fiber, the same superlight material used in Formula 1 race cars and Boeing’s 787 Dreamliner. That sits on a chassis made of aluminum (also superlight) that Justice says meets five-star crash-test equivalency ratings from the National Highway Traffic Safety Administration. So despite being just as sturdy and safe as your car, Justice’s prototype weighs 1,104 pounds, a little more than a third the weight of a typical compact. And its low-profile, swoopy design drastically reduces drag. According to him, those attributes get the car to the 80-mile-per-gallon range. Where the other 20 miles per gallon come from, he won’t tell. (He’ll only say that he buys engines from Honda—the same ones used in the Civic—and “tweaks” them.) But add it all up and you’ve got a car that, according to his tests and computer modeling, gets 104 miles per gallon in the city and 114 on the highway.

What makes the SGT01 really intriguing, though—aside from the fact that Justice will sell you one for about 21 grand—is that virtually every system and component can be pulled out and quickly replaced by someone with no automotive experience. Have a sporty body on your Wikispeed car but want something more practical and sophisticated for carpooling with coworkers? Unbolt it from the chassis, lift it off, and drop on your four-door sedan body. (The carbon fiber construction is so light that two people can do the job without breaking a sweat.) The interior in the car you bought last year looking a little dated? Swap it out for the 2013 model. “Let’s say tomorrow Volvo comes out with an amazing new air bag,” Justice says. “You’d have to buy a new Volvo to get that. Even if they wanted to they couldn’t give it to all of their existing customers. Well, when you modularize a car, suddenly that’s not true anymore.

“Think about your email client—maybe you use Outlook or Gmail,” he goes on. “You don’t have to buy a new computer when you change email clients, right? Imagine if you did.” Ah, computers. This idea of interchangeable, plug-and-play components has been around for years in the computer industry, and that’s where Justice got it. He majored in computer science in college, and today he’s a consultant to software engineering teams. He can’t help but make car design geeky because that’s the way his brain is wired.

Modularity doesn’t just benefit the consumer; it lends itself well to another software industry concept Justice has applied to Wikispeed’s manufacturing process, something computer nerds call agile development. Justice and his volunteers pull out the car’s components, tweak them, and test new versions every seven days. Metal shelves in Justice’s garage are lined with plastic bins that hold car parts in various stages of testing. One houses an accelerator pedal attached to a series of wires that can be hooked up to an engine to develop a more fuel-efficient shifting mechanism. “People coming from other disciplines don’t think that way,” he says. “They say, ‘Well, here’s the best idea I have. Let’s try it.’ And it’s not modular, so it costs a lot to change. They kind of have one shot at it. I created a software project because I didn’t know any better. I did tests first and said, ‘Okay, this is the range of parameters that can achieve more than 100 miles per gallon. What’s the cheapest thing I can do with that design?’ ”

There’s one more explanation for Justice’s irrepressibly awesome attitude. It’s his explanation. “Morale is a multiplier for velocity,” he says. “If there is a conscious reason I’ve wholeheartedly embraced positivity, it’s because I saw how little good was accomplished on low-morale days. And I saw that we got to do completely ridiculous, crazy fucking shit on high-morale days. High morale makes the impossible possible, so it doesn’t seem worth spending my time any other way if I can help it.”

Put another way, he just did the math.