[Scott65]

I would definitely not power the ecu from an alternator connection under any circumstance. Straight from the battery is best, that's why it's advised by the manufacturer. With respect to grounds, do some reading about ground loops. Then ground the ecu, and any wires associated with it either straight to the battery, or to the engine block/head. ALL to the same place, whichever it is.

[JLMounce]

Originally Posted by Scott65

I would definitely not power the ecu from an alternator connection under any circumstance. Straight from the battery is best, that's why it's advised by the manufacturer. With respect to grounds, do some reading about ground loops. Then ground the ecu, and any wires associated with it either straight to the battery, or to the engine block/head. ALL to the same place, whichever it is.

Correct, don't do that, it's too noisy. When you connect directly to the battery, it's acting as a power conditioner.