You’ve probably seen the video. A tiny, silver Smart Fortwo sits idling on a drag strip, looking entirely out of place until it lets out a deafening, high-pitched scream. Then, a massive plume of fire erupts from the rear, and the car vanishes into a cloud of tire smoke and kerosene fumes. It’s the smart car jet engine build, a mechanical fever dream that has racked up millions of views across YouTube and TikTok. But honestly, most of the internet gets the "why" and the "how" completely wrong.
People think it’s just a prank. Or a death wish. In reality, these machines are masterclasses in custom engineering.
Building a smart car jet engine isn't something you do because you want a practical commuter. It is a pursuit of the absurd. You’re taking a car designed for tight European parking spots—a vehicle known for having the structural integrity of a soda can—and shoving a turbine meant for a military aircraft or a heavy-duty generator into the trunk. It’s stupid. It’s dangerous. And it is technically fascinating.
Why a Smart Car? The Physics of the Tiny Turbine
If you wanted to build a jet car, you’d think a long, heavy chassis like a Land Speed Record vehicle would be the way to go. Stability is key when you’re dealing with thrust, right? Well, the folks behind these builds, like Bill Berg of Wildchild Motorsports, chose the Smart car for the exact opposite reason. It’s short. It’s light. It has a wheelbase that makes every twitch of the steering wheel feel like a life-altering decision.
Basically, the power-to-weight ratio becomes hilarious.
When you strip out the tiny three-cylinder engine that usually wheezes out about 70 horsepower and replace it with a General Electric T58-8F turboshaft engine, you aren't just adding power. You are fundamentally changing the car's relationship with gravity. The T58 is a beast. Originally used in helicopters like the Sikorsky SH-3 Sea King, it can pump out roughly 1,400 shaft horsepower. Even when converted to pure thrust, it’s enough to push a 1,600-pound car to speeds that the tires were never, ever rated for.
The Engineering Nightmare Under the Hatch
You can’t just "bolt in" a jet engine. It doesn't work that way.
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Most of these builds, including the famous one featured on Jay Leno’s Garage, require a complete gutting of the rear subframe. You’re essentially building a tubular steel cradle to hold a massive spinning furnace. Then there’s the fuel. Jet engines don’t run on 87-octane pump gas. They drink Jet A or kerosene. This means the builder has to install a custom fuel cell, high-pressure pumps, and a complex cooling system so the interior of the car doesn't reach 400 degrees while you’re sitting at a red light.
Speaking of red lights—how do you drive this thing?
Most smart car jet engine projects are actually "hybrids" in the loosest, most chaotic sense of the word. They often keep a small electric motor or the original front-wheel-drive setup for low-speed maneuvering. Why? Because a jet engine is binary. It’s either "I am a very loud heater" or "I am now moving at 160 mph." There is no middle ground for a grocery run.
The Heat Problem
Let’s talk about the paint. If you’ve ever stood near a turbine, you know the exhaust gas temperature (EGT) is no joke. On a Smart car, the exhaust nozzle is usually inches away from the rear bumper. Builders have to use aerospace-grade heat shielding, often involving ceramic coatings or literal gold foil, to prevent the plastic body panels from melting into a puddle of goo.
It's a constant battle. The heat soak is real.
Myth vs. Reality: It’s Not Actually "Fast" (In the Way You Think)
Here is the nuance that people miss: a jet-powered car is actually a terrible drag racer.
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If you put a smart car jet engine up against a Tesla Model S Plaid or a built pro-mod car, the jet car loses the first 60 feet every single time. Turbines take time to "spool up." There is a massive lag between flooring the pedal and the compressor reaching the RPMs necessary to generate meaningful thrust.
However, once it’s moving? It doesn’t stop pulling. While a piston engine has a power band that drops off, a jet engine just keeps screaming. The acceleration is linear and terrifying. The limitation isn't the engine; it's the fact that the Smart car has the aerodynamics of a brick. At 150 mph, the air wants to lift that short wheelbase off the ground. Most builders have to add lead weights to the front end just to keep the nose down.
The Legal Gray Area
Is a jet-powered Smart car street-legal? Sorta. Maybe. Usually not.
In the United States, "street legal" is a loose term that varies by state. In some places, if it has headlights, turn signals, and a windshield wiper, you can slap a plate on it. But the moment you fire up a T58 turbine on a public road, you’re violating noise ordinances, emissions laws, and probably several "disturbing the peace" statutes. Most of these cars are registered as "specially constructed vehicles."
But let’s be real. You aren't taking this to the DMV. You’re taking it to car shows and closed-course exhibitions where you can melt the asphalt in peace.
The Cost of the Absurd
If you're sitting there thinking, "I want one," bring your checkbook. A used, timed-out surplus jet engine might cost you $15,000 to $30,000. But that’s the cheap part. The custom fabrication, the ECU controllers for the turbine, the fire suppression systems, and the reinforced tires will easily push the build past the $100,000 mark.
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It’s a massive investment in a car that has zero resale value to anyone except a very specific type of eccentric billionaire.
What Most People Get Wrong About Safety
The common perception is that these cars are rolling bombs. That’s actually a bit of an exaggeration. While the fuel is flammable, kerosene is much more stable than gasoline. It won't explode if you drop a match in it. The real danger is "uncontained engine failure."
If a turbine blade snaps at 30,000 RPM, it becomes a piece of shrapnel moving at the speed of sound. This is why professional builders like the Arfons family or modern turbine enthusiasts use "containment rings"—thick bands of Kevlar or heavy steel wrapped around the engine's belly. If the engine blows, the ring catches the pieces so they don't go through the driver's spine.
Actionable Steps for the Aspiring Builder
If you are actually serious about pursuing a smart car jet engine build, or any turbine-powered vehicle, do not start by buying a car. Start with the science.
- Study Small Gas Turbines First: Look into the Boeing 502 or the Garrett GTP series. These are smaller, "man-portable" turbines often used as Ground Power Units (GPUs) for aircraft. They are much easier to understand than a full-sized helicopter engine.
- Join the Communities: Groups like the Gas Turbine Builders’ Association (GTBA) are filled with engineers who have been doing this since the 70s. They will tell you exactly why your fuel system will fail before you spend a dime.
- Understand Thrust vs. Shaft Horsepower: Most people buy a turboshaft engine (which spins a rod) and realize too late they wanted a turbojet (which blows air). Converting one to the other is a massive engineering hurdle.
- Safety Gear is Non-Negotiable: If you’re building this, you need a full fire-suppression system (like a Safecraft setup) and a 10.3-rated roll cage. The Smart car’s factory "Tridion safety cell" wasn't designed for jet-engine-level impacts.
- Check Local Laws: Before you start, look up your state's "experimental vehicle" registration requirements. You might find that a "Kit Car" title is your only path to getting a license plate.
Building a smart car jet engine is the ultimate expression of "because I can." It serves no purpose other than to challenge the laws of physics and make a lot of noise. In a world moving toward silent, efficient EVs, there is something deeply human—and deeply weird—about a tiny car that screams like a fighter jet. It’s a testament to backyard engineering, a middle finger to practicality, and a reminder that with enough kerosene and a welder, almost anything is possible.