Wherefore the muffler ground?

While removing the factory exhaust system from my car, I noticed that for some reason, Mitsubishi saw fit to add a grounding wire between the muffler and the body. Before asking a dumb question on the forum, I did a little searching and found several somewhat plausible reasons, but no real conclusive answer for why this wire exists. Here are the reasons I found:

• It's a supplemental ground for the O2 sensor.
  • This is sorta plausible because the car came with a 1-wire O2 sensor from the factory, but if that's the reason, why put it all the way back at the muffler, when the sensor is in the engine bay? It would be a lot easier and more effective to just directly ground the sensor.
• It prevents static electricity buildup in the exhaust system.
  • I guess I could see some charge being created by the gases flowing through the exhaust system, but static buildup generally happens in materials that aren't very conductive, and the exhaust system is made of steel, with steel/graphite gaskets, and solidly attached to the engine, so it should all be conductive enough that I'm not really sure I buy this one.
• It prevents the exhaust system from rusting out.
  • This seems like it would be tied to the static electricity theory, but if there's actually a voltage difference between the exhaust system and the body at the muffler, adding a path for current to flow between the muffler and the body would appear to create a circuit, which would actually speed up the rust, wouldn't it? Rust is a chemical process and while I think I have a pretty good handle on how electricity works, I'll admit my chemistry knowledge isn't great, so I could be missing something here.

So, does anyone have a better theory about this, or more info to back up any of the ones above? I've never grounded any of the exhaust systems I've built or any of the aftermarket parts I've installed, and on a non-daily-driver "enthusiast" car, I'm not sure it matters, but I can't help but wonder what the engineers were thinking. Maybe it was just superstition.

Red wire for ground doesn't strike me as a factory feature.  

I'm not sure I understand your rubber muffler hanger either.   It looks like the rubber piece is just sitting there but that how it is really hanging is metal to metal. 

It's to dissipate the static charge so you don't get zapped while opening the trunk with your leg close to the exhaust. 

The charge is created by the tire in close proximity to the exhaust behaving like a makeshift Van Der Graaf generator. 
 

actually I just made that up, I'm not sure what it would be used for. Maybe something in manufacturing?

In reply to John Welsh :

That's overspray. The previous owner had the car painted by Maaco.

There are hooks on the body that the rubber donuts hang from, but they're just out of frame.

While I have no explanation for a ground from the muffler, I think the red on that wire is red over spray. 

It's an 1980s turbo car. They tend to run rich on over run and throttle closed deceleration. The ground wire is there to prevent static electricity from causing it to shoot Fireballs or blow up the muffler with the unburned fuel in the exhaust.

The exhaust system is a big antenna, a ground keeps RFI down.

In reply to Dusterbd13-michael :

Definitely some truth in that. The wideband shows that it actually does cut fuel on decel, but the factory tune on these is very rich in general.

In reply to Pete. (l33t FS) :

Anything with mass flow through it creates static electricity.  If you make that system out of multiple different materials (aluminum head, cast turbine, stainless exhaust,etc)  the electric flow greatly accelerates galvanic corrosion across those materials.

So the OEMs will try to dump that flow of electrons off of certain sections individually to keep them from electrically interacting and rusting out (in this case,the exhaust).

It's there to keep the muffler from dragging on the ground when the hangers rust off

In reply to obsolete :

It was an explanation that popped into my head fully formed at a stoplight. I have no idea of its a good one or not, but it made a lot of sense to me....

In reply to Dusterbd13-michael :

Static electricity is not lighting off exhaust farts.

It is normal for an ICE to belch fire especially on decell, unless you have EFI with fuel cut

Pretty sure it's to keep it grounded to the ground.

Toyota later adopted this technology

The exhaust system should be grounded through the exhaust manifolds and engine block.  I don't know why an extra wire would be needed.

Maybe there’s a gigantic capacitor just the other side of the cat.  When the thieving trades try to cut the cat out it discharges and fries the perp.   Gotta have a path to ground for that...

Pete. (l33t FS) said:

The exhaust system is a big antenna, a ground keeps RFI down.

 

 

Came here to say this.  Some engineer probably decided that if a 12-cent wire prevents a few ECMs from having hiccups under warranty, it will pay for itself.

Since it's a Mitsubishi my guess is that the wire does nothing but someday the wire will corrode in the eyelet and cause a no start.