Cummins' Twin Module: 2027 diesel aftertreatment adds electric heating
Cummins' Twin Module Aftertreatment system pairs the familiar DOC-DPF-SCR foundation with two 5 kW electric heaters to keep 2027 X15 and X10 diesels clean in cold starts and stop-and-go work.
- 2027
- 2 × 5 kW
- 48-volt belt-driven
- X15 and X10
What Happened
The hardest emissions conditions for a heavy-duty truck are not steady highway runs but cold starts, low-speed routes, stop-and-go traffic, long idling and changing loads, and an aftertreatment system has to treat exhaust across all of them. The Twin Module Aftertreatment system is Cummins Inc.'s 2027 diesel aftertreatment architecture for X15 and X10 diesel applications, designed for North American on-highway vehicles as emissions standards continue to advance. Cummins says it is not a break from diesel but the next step in the company's continued evolution of diesel technology. It brings updated technology to cold starts, low-load operation, stop-and-go routes, long hauls and tough terrain while staying rooted in a familiar Cummins aftertreatment foundation.
- DOC — the diesel oxidation catalyst converts carbon monoxide and hydrocarbons into less harmful substances such as carbon dioxide and water vapor, and supports regeneration of the diesel particulate filter.
- DPF — the diesel particulate filter captures fine particles from engine combustion, a highly engineered trap for soot also known as particulate matter, with captured material managed over time through regeneration and normal service practices.
- SCR — selective catalytic reduction is the final major stage and focuses on nitrogen oxides, often called NOx.
- DEF — diesel exhaust fluid is a urea-based fluid introduced into the exhaust stream; when it meets hot exhaust and the SCR catalyst, it converts NOx into nitrogen and water vapor.
- Includes the DOC and DPF functions that manage carbon monoxide, hydrocarbons and particulate matter
- Handles NOx reduction after DEF has been introduced and mixed into the exhaust stream
The two-assembly layout is meant to be practical. Cummins designed the system to support a range of vehicle chassis configurations, including under-step and back of cab for on-highway commercial vehicles, which gives OEMs packaging flexibility and lets fleets fit the 2027 system into real truck applications without unnecessary complexity. For DEF dosing, Twin Module uses a single DEF doser rather than dual dosing: DEF is injected once in the body mixer, where it mixes thoroughly before the exhaust reaches the SCR system. Ancillary piping connects the two assemblies, with exhaust moving through the DPF assembly first, passing through the connecting section, and then entering the SCR assembly for the next stage of treatment.
2 × 5 kW
The biggest 2027 update, powered by a 48-volt belt-driven alternator mounted on the engine
The biggest 2027 update is electric heating. SCR catalysts must reach operating temperature before they can convert NOx, and cold starts, low-load operation and low-temperature duty cycles can make it harder for the system to heat up quickly and maintain operating temperature. Twin Module addresses that with two 5 kW electric heater modules powered by a 48-volt belt-driven alternator mounted on the engine, so the system can add heat when and where it is needed instead of relying only on engine heat. Cummins compares it to a kitchen oven that never reaches the right temperature: electric heating accelerates catalyst light-off, the point when the catalyst is warm enough to work effectively, which supports NOx conversion during startup and low-load operation. Twin Module also uses updated catalyst technology in the SCR assembly to improve low-temperature NOx conversion across a wider range of operating conditions.
Cummins designed Twin Module so technicians can service it efficiently. The electric heater modules use V-band clamp connections between the heater and catalyst modules, making them serviceable without replacing the whole assembly, so a heater module that needs attention keeps the job focused on the component that needs it. Cummins also designed the DPF assembly to meet more stringent particulate matter requirements while keeping the same catalyst volumes and the same service intervals, which the company calls a practical benefit of continuity in DPF cleaning intervals for fleets and maintenance teams.
Previously from Cummins Inc.
Cummins previously explained its heater control unit, a device that delivers up to 10 kW to warm aftertreatment catalysts quickly, helping diesel engines meet ultra-low NOx standards. That earlier explainer focused on adding heat to bring catalysts up to working temperature, the same emissions-control problem addressed again here with the Twin Module's electric heating.
Background drawn from MotorClaw's earlier coverage of Cummins Inc.'s official releases.
Why this matters
Twin Module is the aftertreatment architecture Cummins will offer for its 2027 X15 and X10 heavy-duty diesel applications as emissions standards advance, so it matters to the truck OEMs that package it and the fleets that buy the trucks. Cummins says the design keeps the same DPF service intervals and the same familiar building blocks, aiming to limit complexity for maintenance teams.
Terms in This Story
- DOC (diesel oxidation catalyst)
- The aftertreatment stage that converts carbon monoxide and hydrocarbons into less harmful substances such as carbon dioxide and water vapor.
- DPF (diesel particulate filter)
- A device that captures fine soot particles, or particulate matter, from engine combustion.
- SCR (selective catalytic reduction)
- The aftertreatment stage that targets nitrogen oxides, or NOx, using a urea-based fluid.
- DEF (diesel exhaust fluid)
- A urea-based fluid introduced into the exhaust stream that, with the SCR catalyst and hot exhaust, converts NOx into nitrogen and water vapor.
Summarised from the linked release; details can be imperfect — always verify against the original source.