915iS Wiring Questions

[VictorV]

I'm in the process of designing the electrical system for my SS7 which will have a 915iS and VP-X. I'm hoping that someone that
has installed a 915 can answer some questions. I believe that the 915iS is configured the same as the 912iS and has the
same basic components so someone with a 912iS might also be able to help.

1) The installation manual for the 915iS leaves a lot to be desired On page 52 there is a diagram of the overall wiring but the
quality is so crappy it's almost impossible to read. Is there a better version of this diagram somewhere? The equivalent diagram in
the 912iS manual is much higher quality. Can I just use that?

2) The 915iS has a "fusebox" which has the 2 voltage regulators attached to it and some magical circuitry I assume. Typically one would
manually wire a voltage regulator by providing a field power and field sense wire. I don't see this anywhere in the installation manual.
Are those functions built into the 915iS controller already so I don't need to provide them from an external source?

3) Does the 915iS voltage controller have built-in Over-Voltage protection which will disable the generator if necessary?

4) I was planning to install the typical engine sensors which are then connected to the Garmin GEA-24 Engine Information System which sends
that data to the G3X. I see a mention, though, that the 915iS ECU can connect to the CAN bus and provide sensor
info directly to an EFIS. How do I determine which info is already provided by the 915iS ECU to the G3X so that I don't duplicate functionality?

5) I don't see the starter relay mentioned anywhere. Is that already built into the control electronics and all you need to do is provide
a switch that enables it?

Any help would be greatly appreciated!

Victor

[Shadowrider]

Check out PPS from vertical power. I would of incorporated it into my build if it was out when I built. Sorry can’t answer most of your questions, but a few just went down the road your starting and they can chime in. I do know that you can connect the canbus to the 915 ecu, just not sure what sensors you can see as I am also interested. Someone should post a screen shot of what they are getting? Can you see intake temps(manifold temp) EGTs, cht’s?

[VictorV]

Check out PPS from vertical power. I would of incorporated it into my build if it was out when I built. Sorry can’t answer most of your questions, but a few just went down the road your starting and they can chime in. I do know that you can connect the canbus to the 915 ecu, just not sure what sensors you can see as I am also interested. Someone should post a screen shot of what they are getting? Can you see intake temps(manifold temp) EGTs, cht’s?

I actually had the PPS in my design but removed it. The PPS replaces the high-current relays like the starter and mains and simplifies
alternator wiring but I think that most of that is already provided by the 915iS electronics. The only thing the PPS offered that
was left were shunts and those are cheap to buy. The PPS costs $1700 and since my budget is somewhat blown by deciding on
the 915iS it did not make sense to include it anymore. Since I live close to KF I should probably pay a visit and see how they wire
up the 915iS.

Considering the cost it would be nice if the installation document was more clear.

Victor

[Shadowrider]

I hear you. Wish kitfox would update instructions and make a few videos for clarification. FYI you don’t need a shunt with the VPX. It knows amp draw of everything going out and totals them to give you total amp draw.

[Doggitz]

Hello Victor

I am in the exact same spot as you. My 7SS is about ready for fuselage cover and I am already planning the next step - avionics.

I also plan a 915is with a VPX. I will be using GRT avionics instead of Garmin. I am not an electrical engineer, but do have some fundamental knowledge of circuitry.

I agree that the 915is install manual leaves a lot to be desired. The sections that I found most useful are 24, 76, and 77, but you likely know that already.

I have been through the VPX manual several times (haven't bought the actual unit yet) and have some ideas about how I want to configure things. The manual is mostly complete, but requires a lot of digging to find what you are looking for.

Perhaps we can chat off line. If you send me a PM with contact info, would like to talk. We can, of course, post our findings here to benefit other forum members.

Thanks

Fred

[jrd]

Yes the install manual sucks. I am swapping out my ULS for the 912 iS now! As to your question on the fuse box....you do not have a field wire on these alternators, they are permanent magnet generators so they max out at rpm, any extra current is shunted to ground. Because they max out I made a large heat sink for the "B" regulator as it puts out around 33 amps and a lot of heat. The "A" regulator is only 16 amps and handles it OK. And yes Rotax has an automatic overvoltage protection on these voltage regulators...once the wires burn thru it usually stops producing current.

[VictorV]

Yes the install manual sucks. I am swapping out my ULS for the 912 iS now! As to your question on the fuse box....you do not have a field wire on these alternators, they are permanent magnet generators so they max out at rpm, any extra current is shunted to ground. Because they max out I made a large heat sink for the "B" regulator as it puts out around 33 amps and a lot of heat. The "A" regulator is only 16 amps and handles it OK. And yes Rotax has an automatic overvoltage protection on these voltage regulators...once the wires burn thru it usually stops producing current.

Thanks for the info. It would be nice to capture all the stuff we've learned so that others can use it in the future.

Victor