What copy through does
Some Haltech Elite installs use a patch harness, where the Haltech sits alongside the factory ECU instead of replacing it. In that setup, copy through tells the Elite to output whatever fuel and ignition timing the factory ECU is calculating, in the cells you mark. It only works on these patch harness installs, because the factory ECU has to be there producing the values.
The appeal is simple. On a mildly modified engine, the factory calibration is often perfectly good at idle, cruise and light load. Copy through lets you keep that behavior and only tune the areas your modifications actually change, such as full load.
How to set it up
- Open the Base Fuel or Base Ignition table.
- Select the cell, or a block of cells, you want the factory ECU to control.
- Press
Cto set them to copy through.
See selecting cells and modifying tuning tables for the table editing shortcuts.
While the engine is running in a copy through cell, the Elite ignores all of its own corrections. Temperature, acceleration and other corrections you've set up won't be applied there, so the factory ECU is fully in charge of those areas.
Our advice
Make the boundary between copied and Haltech-tuned cells smooth. If your tuned values are far from the factory ones where they meet, you'll feel a step as the engine moves across it. Log both areas and blend the edge cells. If you'd like a hand planning a patch harness tune, book a free consultation.
