Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
SAE J2723 Engine Power Certification: Ensuring Accurate Ratings Through Standardized Testing
SAE J2723 (revised October 2021) provides a standardized process for manufacturers to certify the net or gross power and torque ratings of production engines in accordance with SAE J1349 or SAE J1995. This certification is essential for manufacturers who advertise ratings as “Certified to SAE J1349” or “Certified to SAE J1995.” The standard outlines witness testing requirements, manufacturer responsibilities, and optional methods using isopower charts to account for variations in intake restriction, exhaust backpressure, and charge air cooler effectiveness.
Witness Testing and Remote Witnessing 🛠️
The certification process requires witness testing, where an independent witness verifies that the test facility, equipment, and procedures meet the requirements of SAE J1349 or SAE J1995. Key elements include:
- Witness qualifications: Witnesses must be registered with SAE, experienced in engine testing, and familiar with the applicable standards.
- Witness responsibilities: They verify equipment calibration, test conditions, and data accuracy.
- Remote witnessing: A significant update in the 2021 revision—testing can now be witnessed remotely, enabling greater flexibility while maintaining certification integrity. A remote witness must have real-time access to test data, video feed, and communication with the test cell.
Design Insight: The introduction of remote witnessing reduces logistical barriers and travel costs, allowing more frequent certification checks without compromising oversight.
Testing may be conducted in the manufacturer’s facility or any qualified independent lab that meets ISO 9000/9002 requirements.
Optional Methods Using Isopower Charts for Naturally Aspirated and Boosted Engines
To certify engines for a range of applications with different intake and exhaust restrictions, SAE J2723 provides optional methods that use isopower charts (constant power curves) derived from CAE engine models. These methods apply to both naturally aspirated and boosted engines:
| Engine Type | Variables Addressed | Isopower Chart Use |
|---|---|---|
| Naturally Aspirated | Intake restriction, exhaust backpressure | Test at reference conditions; isopower chart shows permissible variations for same power rating. |
| Boosted (turbocharged/supercharged) | Intake restriction, exhaust backpressure, charge air cooler effectiveness/manifold charge temperature | More complex chart accounting for inlet and exhaust conditions and cooler performance. |
These optional methods allow manufacturers to certify an engine for multiple vehicle installations without repeating full power tests for each configuration. The standard requires that the isopower charts be validated against actual test data and clearly documented.
⚠️ Common Mistake: Using isopower charts without proper validation or failing to update them when engine hardware changes can lead to incorrect certification. Always correlate chart predictions with physical test results.
The 2021 revision also introduces a whitepaper process for submitting optional certifications, providing a clear path for manufacturers to document their methods.
Manufacturer Responsibilities, Production Variation, and FAQs
Manufacturers seeking certification must submit a comprehensive package including:
- Engine description and declared power/torque ratings
- Test results per SAE J1349 or J1995
- A certification statement
- Production variation allowance: The standard permits a margin for natural production variation, so not every engine must be tested. The declared rating represents the minimum performance that all production engines must meet when tested under specified conditions.
The manufacturer must also maintain documentation and notify SAE of any significant changes that could affect power output. SAE maintains a repository of certification data and reviews submissions for completeness.
What qualifications does a witness need?
A witness must be registered with SAE, have engineering competence, and be experienced in engine testing and familiar with SAE J1349 or J1995 requirements.
How is production variation accounted for?
The manufacturer establishes a declared power and torque that accounts for variation. Testing of a representative sample defines the baseline; the rating is set so that all production engines will meet or exceed it when tested per standard procedures.
Can a vehicle manufacturer certify an engine made by another company?
Yes. The standard allows engine certification to be performed by either the engine manufacturer, the vehicle manufacturer, or both collaboratively. For example, witness testing may be done by the engine maker, while the vehicle manufacturer submits the certification documents.
What happens if an engine is modified after certification?
Any significant change that may affect power or torque requires amendment of the certification. The manufacturer must reassess and update SAE as per Section 10 of J2723.
