The Smart Roadster Brabus V6 Biturbo was a factory development prototype built around 2003–2004, pairing two turbocharged three-cylinder engines to produce approximately 170 hp in a mid-rear layout. It never entered production due to cost, packaging and market viability concerns, making it one of the most tantalising what-ifs in Smart’s short history.
For a car that was sold in just four model years and fewer than 43,000 units worldwide, the Smart Roadster 452 generated a remarkable number of ‘nearly was’ moments. None is more captivating than the Brabus V6 Biturbo: a genuine factory-sanctioned prototype that promised supercar-embarrassing performance in a sub-750 kg shell. Understanding what it was, why it died, and what that legacy means for buyers today is essential context — especially if you are deciding how much performance to chase in the used market.
What Was the Smart Roadster Brabus V6 Biturbo?
The concept was elegantly brutal in its engineering logic. Smart’s standard 698cc Mitsubishi-derived three-cylinder turbo produced 60 kW (82 hp) in road trim. Brabus engineers explored the idea of mounting two of these engines longitudinally behind the seats, coupled via a bespoke transaxle to drive the rear wheels. Both units would be turbocharged — hence ‘biturbo’ — giving the car six cylinders in total and earning the V6 designation, even though the architecture was physically two in-line threes rather than a conventional vee configuration. Peak output figures quoted at the time ranged from 160 hp to 170 hp, depending on the source, against a projected kerb weight well under 800 kg. The resulting power-to-weight ratio would have been Ferrari-competitive at the time of development.
The project sat under the Brabus umbrella — the official Mercedes-Benz partner responsible for the road-going 74 kW Brabus model’s full factory specification and performance figures — and was not a one-man shed experiment. Engineers, resources and Mercedes-Benz Group funding were involved. That makes its cancellation all the more striking.
Why the Smart Roadster Brabus V6 Biturbo Never Reached Production
Several interconnected factors killed it. First was cost: engineering a reliable coupling of two separate engine management systems, two gearboxes and two turbocharger systems into a unified drivetrain was enormously complex for a volume production car. The Bosch MEG 1.1 ECU in the standard car was already at the limit of its processing architecture managing one engine; a twin-engine solution would have demanded an entirely new control strategy. Second was packaging. The Smart Roadster’s body-in-white was not designed with a second engine in mind. Crash structure, fire wall integrity, cooling routing and exhaust paths would all have required substantial re-engineering — costs that could not be amortised across a niche model. Third, and perhaps most decisive, was timing: by 2004 Smart was already haemorrhaging money as a brand, and DaimlerChrysler’s appetite for speculative projects was evaporating. The Roadster itself was discontinued in 2006. A halo supercar variant was never going to be approved when the mainstream car was on borrowed time.
There are also credible reports that a prototype was built, driven by development engineers, and found to have significant torque-steer and differential management challenges that would have required further expensive resolution before any customer could safely drive one.
How the Smart Roadster Brabus V6 Biturbo Compares to What Was Actually Sold
Context matters here for buyers. The production Brabus at 74 kW (101 hp) with the chargecooler, uprated injectors and 1.43 bar of boost was already a genuinely fast car in period. A 170 hp version in the same shell would have been in a different dimension. To understand just how the 45 kW, 60 kW and Brabus 74 kW variants stack up against each other on real-world metrics, the gap between the base Lite and the full Brabus is already considerable. The theoretical V6 Biturbo would have sat an entire category above the production Brabus — closer to Lotus Elise 111R territory in performance terms, with far more drama per pound of purchase price.
The production Brabus chargecooler setup is itself a sophisticated piece of engineering. How that intercooling system works gives a sense of how hard Brabus was already pushing the single-engine architecture’s thermal limits — which helps explain why doubling the engine count was such a daunting prospect.
The Smart Roadster Brabus V6 Biturbo’s Influence on Aftermarket Tuning
The prototype never entered production, but its ambition set a benchmark that the aftermarket has been chasing ever since. Modern ECU remapping on the standard 60 kW or Brabus 74 kW platform can extract meaningful gains — our own EVOLUTION map pushes 125 hp from the single 698cc unit — but it is worth being clear-eyed about the thermal ceiling. The Garrett 1238S is a fixed-geometry turbocharger with a pneumatic wastegate operating at up to 1.43 bar in Brabus trim. Pushing beyond that without hardware changes runs into real thermal constraints that the V6 Biturbo project was specifically designed to bypass by adding a second engine rather than over-stressing one.
The lesson from the prototype’s engineering approach is that the right answer to ‘more power’ on the Roadster platform is not always ‘more boost from the same hardware’. Sometimes the architecture itself is the ceiling. For anyone curious about where those thermal limits actually lie, the exhaust gas temperature and boost pressure ceilings of the 1238S make sobering reading before chasing extreme stage tunes.
Should You Chase the V6 Biturbo Dream Today?
If you want a Smart Roadster that approaches V6 Biturbo performance through legitimate means, the honest answer is: manage expectations. No single-engine 452 will reach 170 hp without major hardware investment that exceeds the car’s market value several times over. What you can realistically achieve is a 125 hp, sub-700 kg car that will surprise much larger, more expensive machinery on a twisty road. That is still a remarkable proposition. The sweet spot for most buyers is a sound Brabus 74 kW car — properly checked for the real-world caveats of Brabus ownership, not just the brochure numbers — remapped to extract the final headroom the factory left on the table. The V6 Biturbo belongs to history. The single-engine Brabus, properly sorted, is very much the present.
Frequently Asked Questions
Was the Smart Roadster Brabus V6 Biturbo ever actually built?
Yes, credible reports and automotive historians indicate at least one running prototype was constructed during the 2003–2004 development period. It was driven by Brabus and Smart engineers but never shown publicly in running form, and no production intent was ever officially announced before the project was shelved.
How much power did the Smart Roadster Brabus V6 Biturbo produce?
Quoted figures vary between sources, but approximately 160–170 hp is the figure most consistently cited. Against a projected kerb weight under 800 kg, this would have given a power-to-weight ratio comparable to contemporary sports cars costing several times more.
Why didn’t Smart build the V6 Biturbo as a limited edition?
Engineering complexity, cost per unit, ECU management challenges and Smart’s worsening financial position under DaimlerChrysler all conspired against it. Even a small limited run would have required re-engineering the crash structure, cooling system and drivetrain management at prohibitive cost for a niche model already facing cancellation.
What is the closest production alternative to the V6 Biturbo today?
The production Brabus 74 kW car, remapped to its full potential, is the closest realistic option. A well-sorted Brabus with a quality ECU remap reaches around 110–125 hp in a sub-700 kg shell — not 170 hp, but genuinely fast and far more reliable than any twin-engine conversion could ever be.
