Will changing the stock 10 mm turbo to 40mm on a 91 Eagle Talon TSI AWD burn ECM and if so where can you find an that will handle this turbo?

Changing the turbocharger from a stock 10mm (presumably you mean 10cm^2 or a similar measure of the turbine wheel's area, not the diameter which would be far too small) to a significantly larger 40mm (again, assuming you mean 40cm^2 or a similar measure of the turbine wheel's area) on a 1991 Eagle Talon TSI AWD will almost certainly cause problems, and yes, it could potentially damage the Engine Control Module (ECM) indirectly. It won't likely *fry* the ECM directly, but the ECM will be trying to control an engine operating far outside its parameters.

The problems stem from the drastic increase in airflow the larger turbocharger will produce. The stock ECM is calibrated for the stock turbo and fuel system. A much larger turbo will result in:

* Extremely rich or lean air/fuel mixture: The ECM won't be able to supply enough fuel or control the air/fuel ratio correctly with the increased airflow. This can lead to engine damage (catastrophic engine failure is a real possibility) and potentially damage to the catalytic converter.

* Overboost: The larger turbo may spool up too quickly and create excessive boost pressure that exceeds the limits of the engine's internals (rods, pistons, etc.). This also greatly increases the risk of engine failure.

* Increased stress on other components: The transmission, axles, and drivetrain will experience significantly increased stress with the boosted power output.

* Incorrect ignition timing: The ECM may not be able to adjust the ignition timing appropriately for the vastly changed airflow and resulting combustion conditions.

You will absolutely need a standalone engine management system (EMS) or a significantly upgraded ECU to run a turbocharger this much larger. A stock or even a mildly upgraded ECM won't be able to cope with the changed parameters.

Where to find a suitable ECM/EMS:

You won't find a "stock" ECM that handles this. You'll need an aftermarket solution. Popular choices include:

* AEM Infinity: A very popular and capable standalone EMS.

* Haltech Elite Series: Another high-end standalone option with extensive features.

* MegaSquirt: A more affordable and DIY-friendly option, but requires more technical knowledge to tune.

Remember, upgrading a turbo is a complex process requiring significant mechanical knowledge and expertise. It's not just about swapping parts; you'll need to adjust fuel delivery, ignition timing, and other parameters precisely to avoid catastrophic engine failure. Professional tuning is strongly recommended. A simple turbo swap of this magnitude should ideally be done by an experienced turbocharger specialist. Improper tuning with a larger turbocharger can easily ruin the engine.