Swapping an LS1 into a 4th gen F-body (1993-2002 Camaro/Firebird) often involves using a 24x EFI connection. However, tuning an LT1 (the original engine in some 4th gens) with this setup requires specific adjustments. This guide outlines key differences between the LT1 and LS1, focusing on areas that need modification in an ’01-’02 F-body tune for a ’96 LT1 Camaro.
Engine Tuning for 4th Gen F-Body OBD2 LT1 Swap
Several parameters require adjustments when tuning a 24x equipped LT1. These changes address fundamental differences between the LT1 and LS1 engine management systems.
General Engine Parameters
- Cylinder Volume: This may vary slightly depending on the specific LT1 engine. Verify the actual displacement for accurate calculations.
- Tach Output: Change the tach output setting from 6 to 3 to ensure accurate RPM readings.
Idle Control for LT1 with 24x
The Idle Air Control (IAC) system differs significantly between the LT1 and LS1.
- IAC Counts: The LT1 IAC operates within a range of 0-160 counts with a maximum of 255, while the LS1 ranges from 0-310 with a maximum of 365. Adjust the tune to reflect the LT1’s narrower range. HPTuners now displays the maximum IAC count.
- IAC Reset Position: A value of 160 has proven effective for LT1 IAC reset.
- IAC Steps vs. Effective Area: This table likely requires complete recalibration to match the LT1’s IAC characteristics.
- Desired IAC Area Max: This parameter needs to be adjusted to the LT1’s specific requirements.
Airflow Considerations
- MAF Airflow: While the physical MAF sensor might be the same, tuning the MAF table is crucial for optimal performance with an LT1.
- VE Tables: These tables will require tuning to account for the LT1’s unique volumetric efficiency characteristics.
Fuel System Adjustments for LT1
- Injector Bank Select: Configure the injector bank select to: A, D, F, G = 0 and B, C, E, H = 1 for proper injector firing order.
- Injector Timing: The LS1 uses earlier injector timing than the LT1. Utilize the EOIT (End of Injection Timing) spreadsheet to calculate the correct values for your specific camshaft. Consider a Boundary value of 7.1 as a starting point for a stock LT1.
- Injector Flow Rate: Input a flat value representing your injectors’ flow rate, unlike the varying values used in the LS1 tune.
- After Start Enrichment: LT1 engines require less cold start enrichment than LS1s. Reducing the Initial Adder table by approximately 50% is a good initial adjustment.
Spark Control in LT1 Tuning
- Spark Tables: The LT1 uses MAP vs. RPM for spark control, while the LS1 utilizes Cylinder Air Mass vs. RPM. Consider using spark tables from an L31 van as a starting point, but be prepared for further tuning. Knock Sensor: A knock sensor from a 2002 Express Van 5.7L (part number 10456288) is recommended. Start with the corresponding Express Van knock tables.
Transmission and Fuel System Notes
- Transmission: Specific tuning adjustments for automatic transmissions will vary. Consult resources specific to your transmission type.
- Fuel Sender: Some users have reported unusual fuel gauge behavior after a 411 PCM swap. This may be related to modifications to the fuel pump or float arm.
This guide provides a foundation for tuning a 4th gen F-body LT1 with a 24x EFI system. Remember, these are starting points, and further tuning with a wideband oxygen sensor and data logging is crucial for optimal performance and safety. Always consult reputable tuning resources and forums for additional guidance.
