The Smart Roadster camshaft upgrade is one of the least-discussed but most mechanically interesting modifications you can make to the 698cc three-cylinder engine. Because the platform was never intended as a performance project by Mercedes-Benz, the aftermarket for internal engine parts is thin — but not non-existent. If you are planning a serious build beyond a simple remap, understanding what camshaft options exist, what they actually change, and how they interact with the rest of the engine is essential before spending money. This article covers available profiles, the mechanical realities of fitting non-standard cams, and the supporting modifications you will need to make any camshaft work worthwhile.
Understanding the Stock Camshaft Setup
The Smart Roadster’s engine — a Mitsubishi-derived 698cc turbocharged three-cylinder, mounted mid-rear behind the seats — uses a single overhead camshaft (SOHC) operating both intake and exhaust valves via rocker arms. The architecture is compact and relatively simple, which is both its strength and its limitation when it comes to performance camshaft work.
The standard camshaft profile is tuned for low-end torque and urban driveability. Valve lift and duration are conservative: the engine produces peak torque early and trails off at higher revs, which suits the Softouch automated gearbox’s shift strategy. The result is an engine that feels punchy around 2,500–3,500 rpm but runs out of breath before it approaches the 6,500 rpm redline in any meaningful way. A performance camshaft targets exactly this weakness, shifting the power band higher in the rev range and improving volumetric efficiency at speeds the stock cam cannot exploit.
Before considering cam work, it is worth ensuring your turbo system is healthy. A failing wastegate actuator will mask any power gains from internal modifications and cause boost instability that makes tuning meaningless.
What Camshaft Upgrades Are Actually Available?
This is where honesty matters. The Smart Roadster’s engine shares its basic architecture with certain Mitsubishi three-cylinder units, but the specific bore, stroke, head geometry and cam dimensions mean that off-the-shelf performance camshafts designed for other applications rarely drop straight in. The practical options fall into three categories.
Reground OEM Camshafts
The most accessible route is having your existing camshaft reground by a specialist. A camshaft grinder can increase lift, duration and — to a lesser extent — overlap on the existing billet, provided there is sufficient base circle material to work with. For the Smart Roadster engine, sensible performance grinds typically add 1–2mm of additional lift and extend duration by 20–30 degrees. This shifts the torque curve upward by roughly 500–800 rpm and sharpens mid-range response noticeably. Cost varies by supplier, but expect to pay £150–£300 for the regrind alone, plus machining time and reassembly labour.
Custom-Ground Performance Camshafts
A small number of specialist engine builders — primarily in Germany and the Netherlands, where Smart Roadster enthusiasm remains strong — have produced custom cam profiles for this engine on a semi-bespoke basis. These are not mass-market products and typically require direct contact with the builder. Profiles available as of 2025 range from mild road grinds that retain idle quality and low-end tractability, to more aggressive track-oriented profiles with substantial overlap that demand a supporting remap to prevent idle instability and fuelling errors. If you are pursuing this route, pair it with professional porting and flow work on the cylinder head — the two modifications are highly complementary and share the same head-off labour.
Profile Swaps from Mitsubishi Variants
Some builders have investigated camshaft transplants from related Mitsubishi three-cylinder engines, particularly variants used in kei-car turbocharged applications. Results are mixed. Dimensional compatibility is not guaranteed, and verifying cam journal diameter, lobe position and overall length requires precise measurement before any machine work. This approach suits experienced engine builders only and carries real risk of incompatibility. Treat any forum claims about direct-fit Mitsubishi cams with scepticism unless the specific part numbers and measured clearances are documented.
What Power Gains Can You Expect?
Camshaft work alone on a forced-induction engine is rarely transformative, and the Smart Roadster is no exception. The turbocharger determines ceiling pressure, and the ECU determines fuelling and boost control. A camshaft change without a supporting remap is likely to result in flat spots, poor idle and potentially a net power reduction, because the ECU’s fuel and ignition maps are calibrated for the stock cam timing events.
With a properly matched remap, a reground camshaft on the standard 60kW engine can contribute 8–15 bhp of additional peak power and — more usefully — a wider, flatter torque curve. The real-world sensation is an engine that pulls more eagerly from 3,500 rpm upward and holds its pull through to the redline rather than signing off at 5,000 rpm. Combined with a freer-flowing exhaust and a map calibrated for the new cam profile, some builders have seen the 60kW engine reach 115–120 bhp at the wheels on modest boost. Understanding how boost itself interacts with these changes is fundamental: monitoring and understanding boost pressure becomes even more important when the valve events no longer match the ECU’s stock assumptions.
On the 66kW SB2 Brabus and full 74kW Brabus variants, the standard cam profile is already slightly more aggressive than the base 60kW unit, so the marginal gain from a regrind is smaller — though still worthwhile in the context of a full build.
Supporting Modifications: Making the Cam Work
A camshaft upgrade in isolation is a poor investment. The following supporting modifications are either mandatory or strongly recommended to realise the gains.
ECU Remap
Non-negotiable. The Bosch MEG 1.1 ECU must be recalibrated for the new cam timing. Fuel maps, ignition timing and — on boosted variants — boost targets must all be adjusted to suit the changed volumetric efficiency curve. Our PRO and EVOLUTION remap packages are developed with supporting hardware modifications in mind and can be calibrated to suit specific cam profiles where detailed grind data is provided.
Cylinder Head Work
As noted above, having the head off for a cam swap is the natural time to clean up port entries, improve valve seat geometry and polish combustion chambers. The airflow gains from even modest porting work compound well with improved cam timing.
Valve Springs
Any significant increase in lift or duration should be accompanied by uprated valve springs. The stock springs are calibrated for OEM lift values, and running higher lift on weak springs causes float at high revs — a fast route to bent valves and a destroyed head. Specify spring rate when ordering your cam grind and source matched springs before the engine goes back together.
Exhaust System
A cam with more overlap benefits disproportionately from a lower back-pressure exhaust. If you are running the stock exhaust, you are leaving gains on the table.
Cam Timing and Vernier Adjustability
The Smart Roadster engine uses a timing chain rather than a belt. The OEM cam sprocket has no vernier adjustment — it is a fixed-position fit onto the cam. For serious cam work, fitting an adjustable vernier sprocket allows precise cam timing optimisation on an engine dyno. This is not a beginner modification: advancing or retarding cam timing without dyno feedback introduces risk of valve-to-piston contact, particularly at higher lift values. If you are working with a builder who offers dyno time as part of the build, specify vernier capability from the outset.
The MAP sensor also plays a role in how the ECU interprets the changed breathing characteristics post-cam. A faulty or incorrectly ranged MAP sensor will prevent the ECU from accurately reading the new manifold pressure behaviour the revised cam introduces, particularly at lower revs where overlap affects manifold vacuum.
Is a Camshaft Upgrade Worth It for a Road Car?
For a car used primarily on the road, a mild regrind combined with a remap offers a genuinely noticeable improvement in mid-range character without sacrificing daily usability. The Smart Roadster is a car that rewards driver engagement, and an engine that pulls cleanly to 6,000 rpm transforms the driving experience on B-roads. For track-day or hillclimb use, a more aggressive profile with full supporting modifications is absolutely justifiable — the 698cc engine is small enough that the cost of a full internal refresh, including cam work, remains reasonable compared to larger-displacement projects.
For buyers still choosing their base car before committing to a build, the chassis modifications that transform handling deserve equal attention alongside engine work — the Smart Roadster’s real performance ceiling is often set by its chassis balance as much as its power output.
Conclusion
The Smart Roadster camshaft upgrade market is thin but not barren. A professionally reground camshaft, paired with matched valve springs, cylinder head work and a supporting remap, is a legitimate route to 110–120 bhp on the 60kW engine without pushing boost into reliability-compromising territory. The key rules are simple: never fit a non-standard cam without a remap, always change the valve springs, and use the head-off opportunity to address porting at the same time. Done properly, this is one of the more satisfying internal modifications available to the serious Smart Roadster builder.
