Hi. I’m not an engineer or anything like that. But I am losing sleep over something, trying to understand it.
I am installing an aftermarket ECU module (engine control unit) into a car. It is called a Holley terminator.
So, Holley explicitly states that the main power wire and ground both, for the ECU absolutely MUST be connected directly to the battery cable lug, right on the battery. They claim that it can not be connected to a power junction or buss bar, that has anything else attached to it. Holley claims that this is because of “flyback and transient voltage”. But the thing is, no other factory car manufacturer connects their ECU directly to the battery. They all connect their ECU’s to a power junction stud in the under hood fuse box, which is directly connected to many other loads. No manufacturers are having a problem by doing it this way.
so I have been researching transient voltage in 12v dc systems for days, but I simply can not see why there would be any difference at all from a direct to battery connection, over a junction stud or bus bar connection. How would connecting directly to the battery “protect against flyback or transient voltage” what-so-ever? It’s still the same circuit, and the same main power wire. I could find no reason for this, after searching for days. Even if the Holley ECU did not have TVS devices protecting the ECU, how would hooking it to the battery protect it at all?
I have connected two diagrams. One Holley says is good. The other Holley says absolutely do not do.
I am installing an aftermarket ECU module (engine control unit) into a car. It is called a Holley terminator.
So, Holley explicitly states that the main power wire and ground both, for the ECU absolutely MUST be connected directly to the battery cable lug, right on the battery. They claim that it can not be connected to a power junction or buss bar, that has anything else attached to it. Holley claims that this is because of “flyback and transient voltage”. But the thing is, no other factory car manufacturer connects their ECU directly to the battery. They all connect their ECU’s to a power junction stud in the under hood fuse box, which is directly connected to many other loads. No manufacturers are having a problem by doing it this way.
so I have been researching transient voltage in 12v dc systems for days, but I simply can not see why there would be any difference at all from a direct to battery connection, over a junction stud or bus bar connection. How would connecting directly to the battery “protect against flyback or transient voltage” what-so-ever? It’s still the same circuit, and the same main power wire. I could find no reason for this, after searching for days. Even if the Holley ECU did not have TVS devices protecting the ECU, how would hooking it to the battery protect it at all?
I have connected two diagrams. One Holley says is good. The other Holley says absolutely do not do.
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