Larry DeCamp
Well Known Member
Install docs and recent threads refer to breakers and fuses. I could consult Ross, but for the benefit of all who might care, are fuses as specified by SDS the bottom line for the coils and ECU?s ?
Thanks for the "one fuse for CPU & coil " comment. Less is more. That said, I wondered if the CPU tolerates intermittent cycling ? I was planning to power the cpu from the buss and have a switch for the coil only to " mag Check".
If you want to cut power to check coils, I'd cut coil power rather than CPI module power to do this.
I'm a big fan of ATO type fuses. A fuse block to hold these behind the panel can be added if you were installing EFI in an existing airframe where you had no more breaker space or even in a new airframe.
Do you happen to know of any with a second power input terminal? I'd rather not have both power feeds coming into the same stud.
Otherwise, that's my plan. I'm trying to find one with a removable cover that will protect that power in lug. It looks like they make for a really neat and simple power distribution system.
You don't really want to shut down ECUs to check spark. Currently there is no runup check on the EM-5 so we recommend having coil power switches to check each ignition with dual ECUs.
The ECUs boot up in about .15 seconds and don't command any spark events until 1 crank rev establishes a time interval between magnets. Software changes about 5 years ago allow a seamless transition even turning the ECU off and then on at full rpm.
So if there's no harm done, why not shut off the ECU during spark check? I understand you don't have to if you install coil switches, but it sounds like it doesn't hurt anything if you do...? From my perspective adding separate coil switches is just an unnecessary proliferation of switches that aren't needed for any safety or operational reason that I can see. If there's real value in putting the coils and ECU on separate fuses, they can still be controlled together on one double pole switch.
For the EM-5, we think it's easier to understand what's happening if coil power is cut to check the ignition operation since with dual ECUs (4 cyl.), each ECU is firing one set of plugs and either ECU is running the injectors so you have to remember to switch injectors as well when doing an ignition check.
On 6 cylinder, dual setups we have normal (both), primary and backup positions and depending on that selection, one ECU may be running either all 6 injectors or only 3.
If you want to eliminate some switches, I'd wire the ECUs right to the essential bus with just the breaker or fuse in between. Retain the coil power switches.
Sorry this is in a CPI thread but for dual EM-5, 4 cyl at least, if you don't shut down the ECUs how will you verify the injector relays are working?