In short. CPCB emission norms for gensets are organised by stage, with CPCB IV+ sets using modern engine and aftertreatment technology. Compliance rests on correct category, certification and documentation. Always confirm current limits and dates from official notifications.
Pollutants regulated
- NOx, particulate matter, CO and hydrocarbons.
- Limits depend on stage and engine power band; use the official tables.
What a CPCB IV+ genset typically contains
| Subsystem | Role |
|---|---|
| High-pressure common-rail injection | Precise fuel injection at very high pressure |
| Engine control module | Manages injection, timing and diagnostics |
| Turbocharger and intercooler | Clean, efficient air supply |
| Oxidation catalyst and particulate filter | CO, hydrocarbon and soot control |
| SCR with urea and slip catalyst | NOx reduction; ammonia slip control |
| Sensors | Exhaust temperature, differential pressure, NOx, reagent quality and level |
The reagent is typically a standard urea solution (about 32.5 percent urea in deionised water).
Compliance intelligence
- Identify the set’s category from nameplate and certificate.
- Keep certificates and test reports.
- Maintain reagent quality and system records.
- Do not tamper with emission control systems.
- Track notifications and local rules.
See monitoring and documentation and legacy compliance.
Illustrative example
A buyer compares two sets by price. One lacks the aftertreatment and certification expected for the location. The checklist of subsystems and documents exposes the difference before purchase.
How the subsystems work together
High-pressure common-rail injection delivers fuel at very high pressure, over 2,000 bar in modern designs, with the engine control module timing multiple injections per cycle. This gives finer atomisation and better control, which reduces soot and lets the engine management trade NOx against efficiency. The turbocharger and intercooler supply cool, dense air for cleaner combustion.
Exhaust then passes through the oxidation catalyst, the particulate filter and the SCR system. In SCR, urea solution (about 32.5 percent urea in deionised water) is injected, converts to ammonia, and reduces NOx over the catalyst. A slip catalyst limits any excess ammonia leaving the stack.
Sensors that tell you the system is healthy
| Sensor | What it tells you |
|---|---|
| Exhaust temperature | Catalyst and regeneration conditions |
| Differential pressure across the filter | Soot loading |
| NOx sensor | SCR performance |
| Reagent level and quality | Dosing reliability |
Compliance checklist when buying or inspecting
- Nameplate shows the emission category and manufacturer.
- Type approval or certificate available and matches the engine.
- Aftertreatment components present and untampered.
- Reagent supply and storage arranged.
- Sensors working and alarms visible.
- Maintenance records current.
Common mistakes
- Running without urea or with diluted urea.
- Removing a filter to escape back-pressure alarms.
- Using non-recommended lubricating oil that increases ash.
- Ignoring sensor alarms.
Consequences
Tampering or neglect can lead to non-compliance, penalties, engine damage and loss of warranty. Treat the aftertreatment as part of the engine, not an accessory.
Always verify the rule text
Standards and dates are published by the regulator. Use the official documents for limits and applicability, and keep dated copies.
The master engineering question
Can we show, with paper and with measurements, that this set meets the rule that applies to it?
What to send us
Send nameplate and certificate copies. Send your application details.
Questions engineers ask
What does the plus mean in IV+?
Refer to the official notification for the definition.
Is urea mandatory?
SCR systems need reagent to meet NOx limits.
Can I remove the filter?
No; tampering risks non-compliance and engine problems.
Where are the limits?
In official CPCB publications.
General guidance only. Verify with official notifications.