Updated Chevrolet Performance Stock Calibration and ECU Available May 17, 2021 The latest Chevrolet Performance Stock ECU calibration will be available for swap or purchase on May 17, 2021. The Chevrolet engineers have made the following adjustments:

1. Changed the Rev-Limit Strategy for Vehicle Speed = 0 mph to match non-zero mph, this enables vehicles to behave the same with or without VSS (Vehicle Speed Sensor).

The Original DR525 Cal uses different EOS (Engine Over-Speed) protection depending on vehicle speed, and the protection has a slow response-time if/when speed = 0 mph that may cause problems for vehicles without VSS input (since they always report 0 mph). The slower EOS response causes a brief disruption in engine power, which will degrade vehicle performance (if rev-limit is reached and vehicle doesn't utilize the vehicle speed sensor input to ECU).

The New DR525 Cal has the same (fast) EOS response strategy for all vehicle speeds, so vehicles without VSS will now perform the same as vehicles with VSS (if rev-limit is reached).

2. Optimized the Cal to improve performance using VP Racing Fuels C10 gasoline.

The original DR525 calibration is based on premium pump fuel, and doesn't take full advantage of the VP Racing Fuels C10 fuel properties. The new calibration provides proper spark and fuel changes for increased power with VP Racing Fuels C10 fuel.

IMPORTANT: The calibration changes for VP Racing Fuels C10 gasoline mean the engine cannot operate with premium pump fuel. Using the premium pump fuel can damage the engine due to increased spark advance for use with VP Racing Racing Fuels C10.

3. Changed the Airflow calibration to improve performance with the GM Crate Air-Inlet-Filter Setup.

4. Disabled the use of Purge-Related Fuel Trims due to the DR525 not having the Purge feature.

Chevrolet Performance has released a new ECU under part number 19421203, which contains the new calibration; also available is a new ECU kit (P/N 19421202). The updated ECU is available as a swap with a racer's current ECU or can be purchased without a box swap following the conclusion of the NMRA/NMCA Super Bowl of Street-Legal Drag Racing Presented by HPJ Performance. The previously legal ECUs (P/N 19329004, 19353299, and19354341) and calibration are permitted for continued use in the category, but will be at a disadvantage due to the optimized performance of the new ECU calibration. The new ECU and Calibration will be permitted in Chevrolet Performance Stock Presented by Scoggin-Dickey Parts Center on May 17^th, 2021, following the NMCA mid-season rule adjustments. The 2021 NMCA Class Rules and Updates can be found here: www.nmcadigital.com/2021-class-rules-payouts/