Modern performance cars are loud on cold start — by design. The first 30-60 seconds after starting from cold is when the engine produces the highest emissions, and manufacturers deliberately run an aggressive cold-start strategy to get the catalytic converter up to operating temperature as fast as possible. Higher idle RPM, advanced ignition timing, extra fuel, and on many platforms a defeat of the exhaust flap closure — all aimed at lighting off the cat as quickly as possible to pass emissions cycles.
The result: a thundering cold start that's spectacular at a cars-and-coffee meet and intensely antisocial at 6am in a residential street. Our cold-start noise reduction map smooths the start sequence without compromising warm performance or reliability.
What our cold-start map does
The ECU is reprogrammed to:
- Lower the cold-start idle RPM from the typical 1,200-1,600 RPM down to a more civilised 800-1,100
- Smooth the ignition timing ramp during the first 30-60 seconds to reduce the aggressive popping that creates the loudest sound
- Reduce cold-start fuel enrichment slightly to lower combustion intensity and exhaust note
- Keep the exhaust flap closed during cold-start sequence on platforms where it's normally opened for fast cat warmup (only available where active flaps exist)
- Preserve all warm-engine behaviour exactly as factory — the change affects only the cold-start sequence (typically the first 30-90 seconds after start)
Who it's for
- Performance car owners whose driveways are in residential areas
- Drivers with early-morning starts who'd rather not wake the neighbours
- Track-day cars where the brutal factory cold-start serves no purpose on a track
- Cars fitted with aftermarket exhaust systems where the factory cold-start strategy is already disproportionately loud
- Anyone tired of the dramatic cold-start performance being a daily occurrence
What you DON'T lose
- Warm-engine performance is unchanged — power, torque, throttle response, all factory
- Catalyst light-off still happens — just slightly slower, around 30 seconds longer to reach full operating temperature
- Emissions test cycle compliance is not the goal of this map — it's specifically a quietness-over-emissions trade-off, framed as off-road / motorsport / show use
- Driving dynamics are preserved — only the cold-start aural drama changes
Compatible features
- OBD, bench, and boot-mode flashing — compatible with most major tuning tools
- Fully reversible — flash the original file back to restore factory cold-start behaviour
- Recommended for aftermarket exhaust configurations where the factory cold start is already exaggerated
- Can be combined with burble activation, exhaust flap delete, and stage 1/2/3 power tunes
Legal use
Cold-start noise reduction maps modify the catalyst-warmup strategy. The change increases cold-start emissions slightly during the first 30-90 seconds while the cat is reaching operating temperature. This is illegal for use on the public highway in most jurisdictions, including Ireland, the United Kingdom, and the European Union. BoostCo provides this solution strictly for motorsport, off-road, and show use only. The customer is responsible for ensuring their use complies with local laws.
Supported vehicles
Cold-start noise reduction is most relevant on turbocharged petrol performance engines with aggressive cold-start strategies. Common supported platforms:
BMW
- Bosch MEVD17.2.3, MEVD17.2.4, MEVD17.2.5, MEVD17.2.6, MEVD17.2.G, MEVD17.2.H
- Bosch MG1CS variants (G-chassis cars)
- Siemens MSD80, MSD81, MSD85
- Siemens MSS60 (E9X M3, E92 M3)
Other manufacturers
- Chevrolet (Camaro, Corvette and other LT-series engines)
- Jaguar / Land Rover (F-Type, Range Rover Sport SVR, Defender V8)
- Lamborghini (Huracán, Urus)
- Mercedes-Benz (AMG models with MED17 and MG1 variants)
- Mini (JCW, Cooper S — both BMW Bosch MEVD platforms)
- Porsche (911, 718, Cayenne, Macan, Panamera, Taycan)
- Stellantis / PSA brands (Citroën, Peugeot, DS — selected models)
- Volkswagen Group (Audi RS/S, Bentley, Cupra, Lamborghini, Porsche, Škoda RS, VW R)
If your vehicle isn't listed, contact us — most modern turbocharged petrol performance engines can be supported.
How to order
Read your ECU file using KESS3, K-TAG, Autotuner, MPPS, Dimsport or compatible tool. Submit via the A.R.C.H.I.E. portal with your vehicle details and any aftermarket exhaust modifications. Files typically returned within 5 minutes. Get in touch to confirm compatibility before ordering.
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