Understanding the Smart Roadster boost maps comparison across all four factory variants is essential knowledge for any owner considering a remap, a variant upgrade, or simply wanting to know why their car feels the way it does. The 698cc three-cylinder turbocharged engine is fundamentally the same unit across every Smart Roadster 452, yet DaimlerChrysler calibrated the Bosch MEG 1.1 ECU to deliver four entirely different performance personalities through careful manipulation of boost pressure targets, fuelling tables and ignition timing. This article breaks down each variant’s stock boost strategy, explains what the ECU is actually doing under the bonnet lid (which, remember, is behind the seats), and shows where remapping headroom genuinely exists.
How the MEG 1.1 ECU Controls Boost
Before diving into the numbers, it is worth understanding the mechanism. The Smart Roadster uses a Bosch MEG 1.1 ECU that governs boost via a pneumatic wastegate actuator on the Garrett 1238S turbocharger. There is no electronic boost controller — the ECU modulates a solenoid valve that bleeds pressure away from or towards the wastegate diaphragm, raising or lowering the point at which the wastegate opens and excess exhaust gas bypasses the turbine wheel. The target boost values are stored as three-dimensional maps indexed against engine speed (RPM) and load (manifold pressure or throttle position). When you remap a Smart Roadster, you are fundamentally editing these tables alongside the corresponding fuelling and ignition maps to suit the new pressure target safely.
The firmware version on your ECU matters enormously here. The best and most complete firmware is version 1037371568, which contains the most refined map structure and the largest number of tuneable tables. Older firmware revisions have fewer accessible tables and can limit what a skilled tuner can achieve. If you are serious about extracting performance, confirming your firmware version before committing to a remap is strongly advised.
The 45kW Lite: Low Boost, High Risk
The entry-level 45kW Lite was calibrated to run a peak boost pressure of approximately 0.89 bar (gauge). That is a conservative target that keeps combustion stress low and reduces heat generation — a sensible choice on paper, given that the 45kW variant was built without an oil cooler. The absence of an oil cooler is not a trivial omission: oil temperature management in a turbocharged engine is critical to turbo bearing longevity and piston ring sealing. Running higher boost on a 45kW without addressing oil cooling is a recipe for accelerated wear and the well-documented oil consumption problems that plague the 45kW variant in harder use.
From a map perspective, the 45kW ECU also runs leaner fuelling targets at part load than the 60kW calibration, and its ignition timing is advanced more aggressively at low loads to compensate for the reduced torque output. This means remapping a 45kW is not simply a case of raising the boost target number — the entire fuelling and ignition strategy needs recalibration, and the hardware limitation of no oil cooler must be resolved first. We regard the 45kW as a poor starting point for any serious performance work.
The 60kW Standard: The Sensible Baseline
The standard 60kW is the sweet spot of the range and the most common variant on the road. Its factory boost target peaks at 1.09 bar, and it benefits from the oil cooler that the 45kW lacks. The ECU map is well-structured, with smooth boost build from around 2,000 RPM and a plateau that holds reasonably well through to the 6,500 RPM redline. Torque is rated at 100 Nm, and in good condition the car delivers that figure reliably across a wide rev range.
Crucially, the 60kW platform has substantial headroom. The Garrett 1238S is not working near its efficiency limits at 1.09 bar — the compressor map has meaningful flow capacity available before surge or choke become concerns. The wastegate actuator hardware is shared across all variants, meaning the boost control solenoid can comfortably modulate to higher target pressures. When remapped to our PLUS (100 HP) or PRO (110 HP) calibrations, the 60kW sees boost peaks rising to territory that begins to approach the factory SB2 Brabus figures, but with a fuelling and timing strategy optimised for the specific engine’s condition rather than a one-size production compromise. If you are comparing variants before buying, our detailed breakdown of all four Smart Roadster variants will help you decide which platform gives the best return on a remap investment.
The 66kW SB2 Brabus: Factory Performance Calibration
The 66kW SB2 Brabus represents DaimlerChrysler’s collaboration with Brabus on a volume-production performance variant. Its boost target climbs to 1.33 bar — a meaningful step above the standard 60kW — and the ECU carries revised fuelling maps with richer mixture targets at high load to manage the additional heat generated by the elevated boost. Ignition timing is pulled back slightly compared to the 60kW at peak load, a sensible conservative measure for a production car that must survive varied fuel quality across European markets.
The SB2 Brabus also benefits from a revised intake tract and a higher-flow exhaust, which reduce backpressure and allow the turbocharger to spool more efficiently. The result is a noticeably livelier engine, particularly in the mid-range between 3,000 and 5,000 RPM where the additional boost pressure translates most directly to acceleration. However, the wastegate actuator on SB2 cars is working harder than on a 60kW, and failures are proportionally more common. If you own a 66kW and notice inconsistent boost or flat spots under hard acceleration, our guide on diagnosing boost actuator failure on the Smart Roadster turbo is required reading before touching the ECU.
The 74kW Full Brabus: Factory Maximum
The full 74kW Brabus is the top factory specification, commanding a peak boost pressure of 1.43 bar. This is the highest boost level Smart/Brabus deemed safe and reliable for series production, and the calibration reflects that boundary — fuelling is noticeably richer at wide-open throttle, ignition timing is managed very conservatively, and the ECU incorporates knock retard strategies that are tuned more aggressively than on lower variants. The engine also benefits from Brabus-specific hardware including a larger intercooler, a performance exhaust and a revised air filter arrangement, all of which are prerequisites for running safely at this pressure level.
It is important to note that 1.43 bar is not a hard physical ceiling for the hardware — it is the ceiling Brabus set for warranty and reliability reasons on a production vehicle. With aftermarket supporting modifications and a purpose-written remap, the platform can safely exceed this figure. Our EVOLUTION calibration targets 125 HP and operates at boost pressures that exceed the factory Brabus target while maintaining safe air-fuel ratios and appropriate ignition timing for the specific combination of modifications present. Explore our performance remap packages to see which calibration suits your variant and power goals.
Comparing Boost Maps: What the Numbers Mean in Practice
Peak Boost Pressure Summary
- 45kW Lite: 0.89 bar — conservative, hardware-limited, no oil cooler
- 60kW Standard: 1.09 bar — well-rounded, good headroom, recommended base for remapping
- 66kW SB2 Brabus: 1.33 bar — strong mid-range, wastegate stress, hardware upgrades present
- 74kW Full Brabus: 1.43 bar — factory maximum, richest fuelling, most conservative timing
What Remapping Changes Beyond Peak Boost
A common misconception is that remapping is simply a matter of raising the boost target in a single cell. In reality, a competent Smart Roadster remap involves editing multiple interrelated tables simultaneously: boost target maps (often several, covering different operating modes), injector duration maps for load and RPM, lambda target maps, ignition advance maps, and overrun fuel cut settings. Raising boost without correcting fuelling leans out the mixture under load, raising exhaust gas temperatures and risking detonation. Raising boost without adjusting ignition timing either leaves performance on the table or risks knock damage. The maps must be developed as a coherent system.
The MEG 1.1 ECU stores its calibration data across FLASH memory (the main programme and maps) and a 256-byte EEPROM (immobiliser and variant coding). Understanding this split — and which tables live where — is fundamental to reading and writing maps correctly. For a deep dive into how the ECU stores and protects this data, our explanation of SCN coding and the EEPROM versus FLASH structure covers the architecture in full.
Boost Map Shape Matters as Much as Peak
Peak boost figures are useful for comparison but can mislead. The shape of the boost curve — how quickly pressure builds from idle, how long it holds the plateau, and how gently it tapers near the redline — defines real-world driveability far more than the absolute maximum. The 60kW’s factory map, for example, builds boost relatively gently to avoid traction issues on corner exit, then holds a solid plateau. A skilled remap can sharpen the initial build without making the car nervous, and extend the plateau higher in the rev range where the factory calibration begins to pull boost away conservatively. This is where the craft of map-writing matters: the numbers in the table are only as good as the logic that connects them.
For reference on how turbocharger compressor efficiency relates to boost pressure and airflow, the Garrett turbocharger technical resources provide an excellent grounding in compressor maps and surge/choke boundaries — directly relevant to understanding why there is a practical ceiling on how far a fixed-geometry turbocharger like the 1238S can be pushed. Similarly, a thorough understanding of air-fuel ratio and lambda targets is essential context for anyone evaluating a remap’s fuelling strategy.
Which Variant Is the Best Remap Candidate?
For owners starting from scratch, the 60kW standard is the strongest remap candidate. It has the oil cooler the 45kW lacks, it starts from a lower boost baseline giving more headroom, and it is by far the most common variant meaning parts availability and tuning knowledge are greatest. The full 74kW Brabus is an excellent car in standard form but commands a price premium that narrows the value proposition of further remapping — you are paying more to start closer to the ceiling. The 66kW SB2 occupies an interesting middle ground: good hardware, meaningful headroom, but the wastegate actuator deserves inspection before any boost is added.
This Smart Roadster boost maps comparison makes one thing clear: all four variants share the same fundamental hardware but live in very different ECU worlds. The boost pressure targets, fuelling strategies and ignition timing tables are calibrated to suit each variant’s specific hardware configuration and intended market position. Understanding where your variant sits — and crucially, what its hardware can support — is the essential first step before any remap conversation. Whether you own a standard 60kW looking for a meaningful step forward or a full Brabus seeking the last few horsepower the platform can safely deliver, the boost map is where the story begins.
