The Smart Roadster 45kW to 60kW conversion is one of the most frequently asked questions in Roadster ownership circles. You bought the entry-level Lite, you’ve discovered its limitations, and now you’re wondering whether a software flash or a few hardware swaps could bring it up to the more desirable 60kW standard. It’s a tempting idea — the engine block is essentially the same unit, the turbocharger is similar hardware, and both cars share the same chassis. But as with most things on the Smart Roadster 452, the reality is considerably more nuanced than the forum rumours suggest. This article walks through every dimension of the conversion: hardware differences, ECU constraints, oil system concerns, and whether the whole exercise is actually worth your money and time.
Why the 45kW Exists — and Why It’s the One to Avoid
Smart offered the 45kW Roadster as the entry-level Lite variant, positioning it as a more accessible price point. On paper, the engine displacement is identical — the same 698cc three-cylinder turbocharged unit derived from Mitsubishi’s engineering. In practice, the 45kW and 60kW are meaningfully different cars. The most critical distinction isn’t the power output itself; it’s what was deleted to achieve the lower price. The 45kW Lite omits the engine oil cooler, a component that on the 60kW and above plays a vital role in keeping oil viscosity stable under sustained boost. Without it, oil temperatures climb quickly during spirited driving, oil thins, and the engine begins to consume it at a rate that causes real long-term damage.
The boost pressure also differs significantly. The 45kW runs a wastegate set to approximately 0.89 bar, compared to 1.09 bar on the 60kW. That’s not a marginal difference — it’s a calibration that affects the entire fuelling, ignition timing, and boost control strategy in the ECU. If you’re considering a conversion, understanding exactly how the 45kW, 60kW and Brabus variants differ across every specification is the essential starting point before spending any money.
The Oil Cooler Problem: Hardware First, Always
Before any conversation about ECU maps or firmware, the oil cooler must be addressed. This is non-negotiable. Remapping a 45kW to run 60kW boost pressures without fitting the oil cooler is a reliable way to destroy an engine in an accelerated timeframe. The oil cooler on the 60kW routes engine oil through a small heat exchanger positioned to benefit from airflow, keeping temperatures within a range where the oil maintains its protective film strength.
Fitting the oil cooler is mechanically feasible. It requires sourcing the cooler unit itself, the associated oil lines, the correct banjo fittings, and — depending on the specific 45kW engine bay layout — potentially a bracket or mounting point that may or may not be pre-drilled. Some owners have successfully retrofitted the oil cooler using salvage parts from a 60kW donor car. Others have found the routing more awkward than expected. The oil consumption problem specific to the 45kW is documented in detail and explains precisely why skipping this step is not a viable shortcut.
Beyond the oil cooler, you should inspect the intercooler pipework, check the condition of the boost hoses, and verify the wastegate actuator is functioning correctly. A 45kW that has been run hard without an oil cooler may already have compromised piston rings or valve stem seals, so a compression test before investing further is prudent.
ECU Mapping: What the Software Actually Controls
The Smart Roadster uses the Bosch MEG 1.1 ECU, and the power difference between variants is enforced primarily through the FLASH memory — the main calibration map stored on the ECU’s chip. The 45kW ECU holds a different map set from the 60kW: different boost targets, different fuelling tables, different ignition advance curves, and different torque limiters. Simply applying a 60kW map to a 45kW ECU is technically possible via reflashing, but whether the hardware can support those parameters safely depends entirely on whether you’ve completed the mechanical prerequisites first.
Understanding how the boost maps differ across all four Roadster variants makes it clear that the step from 45kW to 60kW isn’t trivial — you’re asking the turbo to sustain meaningfully higher pressures for longer periods, which feeds back into the oil system argument above. The ECU can be reflashed with a 60kW calibration, but the ECU alone cannot compensate for missing hardware.
There is also the matter of the EEPROM — the 256-byte chip that stores variant-specific data including VIN, immobiliser coding, and certain calibration flags. Some 45kW ECUs carry EEPROM values that identify the car as a Lite variant, which can interact with the SAM unit. This requires careful handling during any conversion to avoid triggering fault codes or immobiliser conflicts.
Firmware Considerations for the Conversion
Alongside the calibration map, the ECU firmware version matters during a conversion. The best available firmware for the MEG 1.1 is 1037371568, which improves gearshift behaviour and resolves several known bugs in earlier firmware revisions. If your 45kW is running older firmware, flashing to 371568 as part of the conversion process is strongly recommended — not for power reasons directly, but because it gives you the cleanest baseline and the most refined Softouch behaviour.
The gearchange improvements delivered by the 371568 firmware update are particularly noticeable on cars that have spent years on older revisions. Pairing a fresh 60kW calibration with modern firmware gives the best possible outcome from the ECU side of the conversion.
The Realistic Cost-Benefit Analysis
Let’s be direct about the economics. A complete 45kW to 60kW conversion done properly — oil cooler retrofit, ECU reflash with a quality 60kW calibration, firmware update, compression check, and associated consumables — is not cheap. Depending on sourcing and labour, you could easily spend £400–£800 or more, and that assumes no engine damage has already occurred from running the 45kW hard without an oil cooler.
For that budget, you might instead find a 60kW car in good condition for a reasonable premium over the 45kW purchase price, particularly at the lower end of the market. The 60kW is simply a better-engineered vehicle as standard. If, however, you already own a 45kW in excellent mechanical condition, the conversion can absolutely deliver 60kW performance — and with a quality remap applied, you can push well beyond that. Our Stage 1 remap delivers genuine, measured power gains on a properly prepared 60kW-equivalent base, making the investment worthwhile if the foundation is solid.
If your ambitions extend beyond 60kW equivalence, it’s worth understanding what hardware modifications are needed before a Stage 2 remap, since a converted 45kW that then moves to higher boost levels will face the same demands as any other car pushing into that territory.
What You Actually Need: A Conversion Checklist
- Oil cooler retrofit — mandatory before any boost increase. Source from a 60kW donor or new old stock.
- Compression and leakdown test — confirm the engine hasn’t already suffered damage from oil thinning.
- Boost hose and intercooler inspection — replace any cracked or weeping hoses before increasing boost.
- Wastegate actuator check — verify the actuator is functioning and set to the correct pressure for 60kW operation.
- ECU reflash — apply a 60kW calibration (or a quality custom remap) with the correct firmware version.
- EEPROM review — check and correct any Lite-variant flags in the EEPROM to avoid SAM conflicts.
- Post-conversion data logging — verify boost, fuelling and temperatures are within expected parameters after the flash.
Every item on this list matters. Skipping any one of them introduces a failure point that will eventually surface, usually at the worst possible moment.
Is the Smart Roadster 45kW to 60kW Conversion Worth It?
The answer is: yes, but only if approached correctly and only if the engine is in good health. A 45kW Roadster with a freshly retrofitted oil cooler, a clean compression test, and a properly calibrated ECU remap is a genuinely enjoyable car that performs comparably to a standard 60kW — and can exceed it with the right calibration. The conversion is not a simple plug-and-play exercise, and anyone selling it as such is cutting corners that will cost you later. Done properly, however, it transforms the most compromised variant of the Roadster into something much closer to what Smart should have built in the first place.
For reference on air-fuel ratio management and how boost affects fuelling demands, the engineering principles behind air-fuel ratio explain why simply raising boost without recalibrating fuelling causes problems. The Bosch lambda sensor documentation is also useful context for understanding how the MEG 1.1 manages closed-loop fuelling corrections under varying boost levels. Finally, for community-sourced data on 45kW conversion experiences, the Smart Car of America forum threads on 45kW upgrades document real-world results from owners who have attempted this conversion with varying degrees of thoroughness.
The Smart Roadster 45kW to 60kW conversion is one of the more satisfying projects in the Roadster community when executed with the right knowledge and the right sequence. Hardware first, ECU second, data logging third. Get those three steps in order and you’ll have a car that genuinely punches above the standard 60kW baseline — making the Lite variant’s original cost saving feel considerably less relevant.
