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colorado80439
03-31-2021, 08:13 PM
Looking for suggestions, we are chassis wiring and do not have the engine wiring harness yet. (E38 ecu) we're installing a battery disconnect next to the battery controlled from a toggle switch at the instrument panel. I'm questioning whether we need to have constant power to the ECU if I will be using the battery disconnect frequently. IE bypassing the battery disconnect to power the ECU

Thanks!!
dhutton
04-01-2021, 04:31 AM
Yes you do or you will lose all your fuel trims etc every time you remove power.

Don
colorado80439
04-01-2021, 06:13 PM
Yes you do or you will lose all your fuel trims etc every time you remove power.

Don

Thanks Don, you're the man.
65 Drop Top
04-01-2021, 10:52 PM
I believe you can use a small fused jumper wire to keep the ecu memory.
colorado80439
04-02-2021, 06:04 AM
I believe you can use a small fused jumper wire to keep the ecu memory.

OH! I like that idea, I'll research that for sure
Thanks so much!!
572Camaro
04-02-2021, 06:53 AM
American Autowire sells a “lifeline” which is a small circuit breaker that can bypass your main disconnect switch. If you trip the breaker, it auto resets.

I don’t know anything about your ECU but most aftermarket EFI companies want you to run power and ground directly to the battery.
I run FAST and they demand it due to electrical noise.
65 Drop Top
04-02-2021, 11:24 AM
I suppose a breaker would be better than a fuse.

Another option, which is more involved and costs more, would be to use a battery back up. I saw a guy use one of those mini lithium ion jump starter batteries. He used it primarily for car stereo memory, but ecu memory should be the same. And if your car battery ever dies, this can jump start it. It’ll charge phones or laptops too.
colorado80439
04-03-2021, 05:23 PM
American Autowire sells a “lifeline” which is a small circuit breaker that can bypass your main disconnect switch. If you trip the breaker, it auto resets.

I don’t know anything about your ECU but most aftermarket EFI companies want you to run power and ground directly to the battery.
I run FAST and they demand it due to electrical noise.

That's great, I think I may run a 20 amp version so I can use the power door locks with the battery disconnect open.