why a ground mod?

[tom klein]

i've found a whole bunch of messages online about ground mods for
scoobies, including commercial kits, reviews, and diy tips (with lots
of pictures).

why is this necessary? are the factory ground wires too small (which i
doubt), or do the grounding points corrode, or what? and since all the
kits (and diy mods) go back to the factory grounding points, wouldn't
you get the same effect by cleaning up those points, making sure you
had good contact, and then coating them with an anti-corrosion
compound? also, why is everybody using insulated wire for ground? (is
red wire really a lot better than black?)

just curious....



........ tom klein

 

[-rick-]

why is this necessary? are the factory ground wires too small (which i
doubt), or do the grounding points corrode, or what? and since all the
kits (and diy mods) go back to the factory grounding points, wouldn't
you get the same effect by cleaning up those points, making sure you had
good contact, and then coating them with an anti-corrosion compound?

I'd say you have it figured out pretty well.

-rick-

 

[Anarky]

Well this old keeps popping it head up,The reason for doing it is that
Subarus have a bad earthing system and as all of the sensors mounted on
the engine send back a pulse or a varible volt to the ECU if the sensor
does not see a true 12-14 volt then the ecu sees a lesser value as well
and does not set its parameters correctly..
My '90 Legacy GT(this is a Jap import modeel in New Zealand so has the
EJ20T engine) made huge improvements just by earthing the engine I used
my own earthing points mind you mainly on the intake manifold

DILLIGAF
DJ

 

[tom klein]

okay, this is the part i'm trying to understand.

what is a "bad earthing system"? was the wire undersized, or was there
a corrosion problem? is this a design "feature" (poor engineering), or
a maintenance issue (clean contacts periodically)?

specifically, what problems did you have that were fixed?

also, why use "your own earthing points"? is there something wrong
with the ones that subaru designed? (i.e. were they in corrosion-prone
areas, or were there disconnected areas that you were trying to reach?)

i know it's a lot of questions, but all the previous discussions seem
to be full of WHAT and HOW, with very little WHY.


........ tom klein

 

[Edward Hayes]

I understand that the factory designed ground system is more than
adequate. However; it seems that some cars are delivered with the
ground lugs being attached over a painted surface so that the mounting
screw is expected to transfer the voltage. Sometimes moister/rust
impedes the connection. This requires that the connections be removed,
cleaned and reinstalled. Absolutely NO NEED to purchase a second
aftermarket grounding kit. I am only familiar with later model
Subaru's say from 1995- present so it may be an issue with old
vehicles.

 

[Anarky]

ok it fixed a hesitation that I had at full boost(15 psi) as well as it
idled alot smoother,I used my own earthing points because I decided
that the engine needed definate earthing to the intake manifold and to
the block of the engine also decided that the sensors on the RHS front
fender could do with an earth as well,So I went from LHS strut tower to
Battery - terminal to LHS of the intake manifold to rear of the
alternator to RHS of intake manifold to sensors on RHS inner front
fender to RHS strut tower.You can just clean exisiting earth point and
do regular maintenance as well and that should be alright for most,my
Legacy is no longer stock and hasnt been so for 150,000 Km and I swear
that the earthing system has helped with the longevity of the engine

 

[CompUser]

nospam@ecologicaltechcom>,
(e-mail address removed) says...

okay, this is the part i'm trying to understand.

what is a "bad earthing system"? was the wire undersized, or was there
a corrosion problem? is this a design "feature" (poor engineering), or
a maintenance issue (clean contacts periodically)?

All the above.

Multiple 12 Ga hot leads running to single 20
ground line (see headlamp assy); grounding
ring terminals mounted over intact paint with
*flat* washers. No use of starwashers; minimal
use of anticorrosion compounds.

Saying the existing system is fine---goes well
with insisting that the only way to disconnect
the battery is by disconnecting the negative
terminal ;-)

 

[Philip Procter]

I don't know if this is the reason in the Subies, but for computers
and high end electronics the problem is due to multiple grounding
points.

If the grounds are not at identical potential, there will be
electrical leakage between the grounds. Even in a home stereo a
misplaced ground wire or a reversed mains plug can lead to easily
audible hum. Since many (most?) sensors in a car operate on a voltage
difference, any change to the 0v point would mess up the value the
coputer uses for its adjustments.

If it were just a matter of ground resistance, say from poor contact,
I'd expect the performance inprovent from the kits to be temporary.
Corrosion under-hood is inevitable.

The few reviews of star ground systems I've read (none specifically
for Subies) have said that they are a tweakers delight. You have to
experiment like crazy and may or may not see any improvement. Unless
you have a dyno in your garage, those are worse odds than installing a
CAI kit.

Philip

 

[Jim Stewart]

I don't know if this is the reason in the Subies, but for computers
and high end electronics the problem is due to multiple grounding
points.

Subies have multiple ground points from the
factory. Take a look at a wiring diagram.

If the grounds are not at identical potential, there will be
electrical leakage between the grounds. Even in a home stereo a
misplaced ground wire or a reversed mains plug can lead to easily
audible hum. Since many (most?) sensors in a car operate on a voltage
difference, any change to the 0v point would mess up the value the
coputer uses for its adjustments.

I've looked at my Outback's wiring diagram and
all of the critical sensors use a separate
return wire. As a result, their output is not
referenced to chassis ground. Reducing ground
strap resistance will not affect them.

The hum on your stereo is because the signal
has to return on the ground wire. On pro audio
equipment, as on the subaru sensors, there is
a separate return line for the signal and a
ground that is *only* a ground and is not
connected to the signal. That's the correct
way to do it.

If it were just a matter of ground resistance, say from poor contact,
I'd expect the performance inprovent from the kits to be temporary.
Corrosion under-hood is inevitable.

The few reviews of star ground systems I've read (none specifically
for Subies) have said that they are a tweakers delight. You have to
experiment like crazy and may or may not see any improvement. Unless
you have a dyno in your garage, those are worse odds than installing a
CAI kit.

I maintain that they won't hurt anything and
may help. Some people have seen a noticeable
improvement without resorting to a dyno.