582 electrical grounding question

[beeryboats]

I'm a bit of a fanatic about good grounds as they can be a real bugger to trouble shoot. I'm re-installing my 582 and cleaning up the engine wiring mess the builder made. I have the ground coming from the "alternator" and a ground from the regulator that go together. Also in that connection a ground that goes to the engine. Shouldn't I also have a ground from the engine to the airframe? Looking at the engine mounts I don't see a good ground unless it is by accident through something else. Seems to me there should be a ground strap from the engine to the engine mount bolt that goes through the lord mount.

[Dave S]

Hi Jay,

Haven't seen any specific answers on your ground question so thought I'd give it shot.

If you have access to the original build manual from the kit manufacturer, check the engine / FFW section of the manual and see if they have a 582 specific guide for the basic electrical system/ground.

Normaly there should be a ground cable to the airframe from the engine of the same gauge as the hot cable for the starter (depending on how the battery is grounded). In the case of our 912 kitfox, the engine mount has a tab welded to one of the engine mount tubes on the starboard side to be used for the ground per the installation manual - the ground cable from the battery and the ground cable from the engine meet at this spot. With a different engine mount as for the 582 I would expect something different but the same idea applies.

What you figure is correct......without a proper ground betsween the airframe and engine, if the battery is grounded to the airframe but not to the engine - the current is going to flow in some peculiar places like the choke cable or throttle cable - on startup the current is a lot higher than in run mode. If the battery is directly grounded to the engine, a case may be made that the airframe ground would not need to be as heavy, but there shoud still be one.

I realize that if you are not the builder, you might not have the original build manual but I am pretty sure the engine/ FFW/ final assembly instructions should have the information you are looking for on your particular aircraft.

Sincerely,

Dave S
KF 7 Trigear (currently grounded due to a leaking radiator)
912ULS Warp Drive

St Paul, MN

[Av8r_Sed]

Jay,
Check out this previous thread: http://www.teamkitfox.com/Forums/sho...ghlight=ground

I did as many posted in that thread, a single point ground at one of the engine mount bolts through the firewall. I think I put in a longer bolt to allow a second nut and star washer for the electrical connections. I did have a bonding wire running from the engine to that point as well as negative battery lead and grounding wire from my ground distribution farm behind the instrument panel.

Also it might make sense to move this thread to the Electrical/... forums.

[beeryboats]

It just dawned on me that the starter ground cable goes to the lower engine mount bolt. That means the ground is through the starter housing. I'm guess I'm good. I'll just ground the alternator to the engine case.
Thanks all,
Jay

[Av8r_Sed]

What alternator on a 582??? Are you talking about grounding the output of the regulator/ rectifier?

[beeryboats]

Hi Paul,
Yes I guess so. I hate to sound so vague, but it serves the same purpose as an alternator. When I removed the engine there was a ground between the "alternator" for lack of a better word, the regulator, and the engine. My question is should the engine case and the airframe be grounded together. Or will that cause unwanted engine noise in the radio?

From an earlier post I thought the engine was grounded to the airframe through the starter ground, but maybe not. I guess it couldn't hurt to run a ground strap from the engine case to the engine mount bolt.
Jay

[Av8r_Sed]

If you have a good size wire running from the starter to the engine mount bolt, you shold be good.

Most radio noise from the engine comes from the ignition. Resistor wire and plugs usually keep this in check.

[beeryboats]

Got it sorted out tonight. The brown wire from the engine is the ground from the engine case, it goes to the regulator and splits off. I ran it to the firewall engine mount bolt. That should make everyone happy. Now, if I only had 6 feet of radiator hose I could finish that tonight....