Any need to isolate mag wires?

[alpinelakespilot2000]

I assume this must have been discussed before, but couldn't find anything in the archives...

Van's electrical dwgs seem to imply that the shielded mag. wires (along with the large power cable coming off the alt. c/b) should pass through their own hole in the firewall on the left side of the fuse. I'm wondering if I'm reading to much into Van's cryptic drawings.

Is it really necessary to run the shielded mag wires by themselves, or could I run them through the same hole I'm planning to run my Dynon 180 engine sensor wire harnesses through? Needless to say, I'm trying to minimize the number of holes in my firewall.

Thanks.

[elippse]

Originally Posted by alpinelakespilot2000

I assume this must have been discussed before, but couldn't find anything in the archives...

Van's electrical dwgs seem to imply that the shielded mag. wires (along with the large power cable coming off the alt. c/b) should pass through their own hole in the firewall on the left side of the fuse. I'm wondering if I'm reading to much into Van's cryptic drawings.

Is it really necessary to run the shielded mag wires by themselves, or could I run them through the same hole I'm planning to run my Dynon 180 engine sensor wire harnesses through? Needless to say, I'm trying to minimize the number of holes in my firewall.

Thanks.

A good rule of thumb is to separate high power/pulse wiring from low-level signals. Unless a shielded wire has a solid outer conductor it will radiate through the spaces in the braided shield. I've not seen the isolation data, though, for shielded wire with an overall foil shield, which, if over 100dB, should be OK. If by Mag wire you are referring to the "P" lead, it has very high voltage pulses with each plug firing which generate lots of harmonics! The alternator output also has pulsed output because of the commutating/rectifying diodes and can also have harmonics which will cause alternator whine.

[Radomir]

If you're looking for real-world experience -- it should be OK.. I'd drill a separate hole only if you find out it's necessary. (assuming using Slick mags)... I don't know anyone around that has this routed separately... and I haven't heard any noise in any of those planes.