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Rusefi driving of ecu relay
Posted: Mon Apr 06, 2020 8:12 am
by JPh
I have a question about how MRE drives the ecu relay.
I need to drive this relay on my car because it powers not only the ecu but other main functions.
I don't want to change that because I have to swap often between oem ecu and MRE.
Does MRE drive this relay? What's the logic of this drive?
If not how can I power the relay to have engine working?
Re: Rusefi driving of ecu relay
Posted: Mon Apr 06, 2020 8:23 am
by mck1117
JPh wrote: ↑Mon Apr 06, 2020 8:12 am
I have a question about how MRE drives the ecu relay.
I need to drive this relay on my car because it powers not only the ecu but other main functions.
I don't want to change that because I have to swap often between oem ecu and MRE.
Does MRE drive this relay? What's the logic of this drive?
If not how can I power the relay to have engine working?
MRE has a dedicated relay pin that's activated (pulled low - other side of the coil goes to battery +) when the ECU is turned on. Whenever the ECU has power, the main relay is activated.
Re: Rusefi driving of ecu relay
Posted: Mon Apr 06, 2020 8:25 am
by Crazy Striker
The main relay is either powered by the immobilizer/steering column or by the ECU depending on the OEM will.
If it is powered by the immobilizer, you can power the ECU through the main relay output and it will be transparent both on the car OEM harness side and for the ECU. In that case you don't have to wire ECU main relay output or configure it inside TunerStudio.
If the ECU needs to actuate the main relay, you have to power ECU using a 5A fused +12V which is hot when ignition is on as well as when the engine is cranking. Then you have to wire main relay coil ground to a lowside driver and set it as the main relay output. You can control the working of this output using console commands or magic test buttons in Tunerstudio. You could hear the relay click and maybe check voltage on systems wired to the relay.
So to sum up it depends heavily on OEM wiring
Re: Rusefi driving of ecu relay
Posted: Mon Apr 06, 2020 1:14 pm
by AndreyB
Re: Rusefi driving of ecu relay
Posted: Mon Apr 06, 2020 3:36 pm
by kb1gtt
software controlled always on when rusEFI is on. AKA FSIO could do different logic if so required. Am I correct about that?
Re: Rusefi driving of ecu relay
Posted: Mon Apr 06, 2020 3:39 pm
by AndreyB
kb1gtt wrote: ↑Mon Apr 06, 2020 3:36 pm
software controlled always on when rusEFI is on. AKA FSIO could do different logic if so required. Am I correct about that?
Yes and no.
Yes, FSIO drives ecu relay on some boards like Frankenso via rusEfi software.
No, on microRusEfi it's completely by TLE8888 without any rusEfi anywhere in sight.