Any questions you have before you begin buying, building and installing.
By MyWheelIsSquare
#50824
What are the recommended wire gauges for the different wires going to and from the speeduino? I thought I had seen it once in the speeduino wiki page but could not find it again. Maybe I was confused. Best I found was in http://www.megamanual.com/v22manual/mwire.htm, but it only shows wire size based on current and length; I do not know the currents in use.

For some reason 20 gauge is on my head...
By dazq
#50825
MyWheelIsSquare wrote: Fri Jun 04, 2021 9:26 am What are the recommended wire gauges for the different wires going to and from the speeduino? I thought I had seen it once in the speeduino wiki page but could not find it again. Maybe I was confused. Best I found was in http://www.megamanual.com/v22manual/mwire.htm, but it only shows wire size based on current and length; I do not know the currents in use.

For some reason 20 gauge is on my head...
As you correctly say wire size is based on length and current draw.
You can calculate current draw using ohm's law.
Unless you have dramatically changed the current draw of the injectors or coils then what the OEM used would be a good guide ( many including myself use OEM harnesses to build our new looms, subject to condition obviously).
By MyWheelIsSquare
#50826
Thanks for the info. I was planning on running an entire new harness (with its own connectors) so I can reverse to old system as needed. As this is a Volvo 740, getting to the relays' sockets is not an issue.
By dazq
#50827
MyWheelIsSquare wrote: Fri Jun 04, 2021 10:06 am Thanks for the info. I was planning on running an entire new harness (with its own connectors) so I can reverse to old system as needed. As this is a Volvo 740, getting to the relays' sockets is not an issue.
"Relays sockets" ? Not sure I understand that part?

But if you want to be able to switch between OEM and speedy why not fit the same ECU connector as the OEM has? Or if you can't do that just add a new plug for speedy to the existing loom( leaving the old one there for the old OEM ECU if you switch back).I did the later on my first speedy build ,use OEM loom with old ECU connector and a new one for speedy.
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By PSIG
#50832
+1, you can just splice Speeduino wires into the OEM ECM harness near the ECM connector, similar to a piggyback installation (Y-harness). You just don't connect both ECMs at the same time. Plug-in whichever ECM you wish to use today. 8-)

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