DUH!!! I didnt really look to much at the motor... I know there is a ground strap there for the 2.8 too. Im just so used to seeing a 2.8, I didnt even consider a 2.5... SORRY!!!!!
The one that I got is not the EXACT same strap but similar, I got mine at AutoZone. Just go to the isle with the battery cables - it was there.
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10:26 AM
Richjk21 Member
Posts: 2228 From: Central Square NY, USA Registered: Feb 2006
If I remember correctly it goes to the bolt that holds the hoist bracket. It is directly above the exhaust manifold on the closest cylinder to the pulleys.
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12:28 AM
Toddster Member
Posts: 20871 From: Roswell, Georgia Registered: May 2001
On the 2.8, the ground goes from the decklid hinge to where? Mine's gone...
It goes to the same place (front left corner of the engine block). you will see a stud there on the head. You REALLY need one. If you don't have it you are straining the electrical system and will eventually have a major electrical systems failure. Don't use a plain wire either, use a proper ground strap. Negative current flows around the outside of the wire, not the inside like Positive current. That is the reason for the large flat design (maximum surface area).
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11:03 AM
Marvin McInnis Member
Posts: 11599 From: ~ Kansas City, USA Registered: Apr 2002
Negative current flows around the outside of the wire, not the inside like Positive current. That is the reason for the large flat design (maximum surface area).
????? Would you like to reconsider that?
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11:19 AM
Toddster Member
Posts: 20871 From: Roswell, Georgia Registered: May 2001
Let's not get into a scientific dissertation of electron current versus electric current. I know free electrons are negatively charged. The point is that the design of the strap is to allow maximum flow of electrons, which go around the outside of the wire.
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11:48 AM
Raydar Member
Posts: 41265 From: Carrollton GA. Out in the... country. Registered: Oct 1999
The point is that the design of the strap is to allow maximum flow of electrons, which go around the outside of the wire.
The electrical "skin effect" does exist, but it's simply not a significant factor in most automotive electrical systems.
At it's simplest level, "skin effect" is the term applied to the phenomenon that about 2/3 (or, more precisely, 1 - 1/e) of an AC current flowing through a conductor will be found within "skin depth" d of the outer surface of the wire. The depth d is inversely proportional to frequency, and for a copper wire in air can be reduced to a simple empirical formula:
d = 2.6 / sqrt (f)
where:
d = skin depth in inches f = frequency in Hz
Probably the highest current intermittent load on the Fiero electrical system is the ignition, which will have a maximum frequency of about 300 Hz (6000 rpm x 3 ignition events per crankshaft revolution of a V6). At that frequency the skin depth d will be about 0.15 inch ... significantly larger than any single wire used in the Fiero except for the battery and starter cables. Q.E.D.
The real reason for using a flat braided ground strap in an automobile ... or for using stranded wire rather than cheaper solid wire, for that matter ... is its mechanical flexibility.
Probably the highest current intermittent load on the Fiero electrical system is the ignition, which will have a maximum frequency of about 300 Hz (6000 rpm x 3 ignition events per crankshaft revolution of a V6). At that frequency the skin depth d will be about 0.15 inch ... significantly larger than any single wire used in the Fiero except for the battery and starter cables. Q.E.D.
But ignition systems generate pulses that contain much higher frequencies. By your math, 300 pulses per second. If 300 Hz was the highest frequency generated by the ignition, there would never be any radio interference. And therefore there would also be no need for the strap from the rear deck lid.
quote
Originally posted by Marvin McInnis: The real reason for using a flat braided ground strap in an automobile ... or for using stranded wire rather than cheaper solid wire, for that matter ... is its mechanical flexibility.
Mechanical flexibility is definately a requirement, but I think the real reason for replacing a 20 yr old gnd strap is to improve the connections. The crimped connections at each end of the strap, the strap to engine connections, and the strap to chassis connections, are probably all degraded. I haven't replaced mine yet, but I am planning to. Especially after seeing what improved connections have done for my 30 yr old motorcycle.
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11:10 AM
Marvin McInnis Member
Posts: 11599 From: ~ Kansas City, USA Registered: Apr 2002
But ignition systems generate pulses that contain much higher frequencies. ... If 300 Hz was the highest frequency generated by the ignition, there would never be any radio interference. And therefore there would also be no need for the strap from the rear deck lid.
You are correct that DC pulses contain higher order harmonics that are many multiples of the fundamental pulse frequency, but the energy content of those harmonics generally drops off exponentially with frequency. Second, virtually all the radio interference you speak of comes from resonances on the secondary (high voltage) side of the spark coil, not from the primary (12 volt) side. Incidentally, that's the purpose of resistor spark plugs and resistive spark plug wires ... to damp those resonances.
quote
... I think the real reason for replacing a 20 yr old gnd strap is to improve the connections.
I agree that's a good reason to replace an old ground strap ... but I was talking about the reason for using a braided strap (or stranded wire) in the first place.
[This message has been edited by Marvin McInnis (edited 06-18-2007).]
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11:53 AM
PFF
System Bot
spark1 Member
Posts: 11159 From: Benton County, OR Registered: Dec 2002
The strap to the deck lid serves only one purpose, to ground the RF shield.
Are we all talking about the same thing? The "strap" you describe is a plain, insulated wire connected to the deck lid and grounded at the left rear lid hinge. At least it's that way on '88s. And yes, I agree that skin effect is significant at RF frequencies.
But the "ground strap" that jetman is talking about is the braided bonding strap connected between the front of the engine block (the forward head on V6es) and grounded to the chassis at the right hinge.
[This message has been edited by Marvin McInnis (edited 06-18-2007).]
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02:58 PM
spark1 Member
Posts: 11159 From: Benton County, OR Registered: Dec 2002
One thing I would add is buy a tube of the copper connector lube/improver they sell at most auto stores. it has bits of copper in the silicone grease and after you clean the heck out of the block and connectors put it on everything and volt it together, do the same to the firewall. It will significantly reduce corrosion problems and water ingress that causes problems in the grounding points.
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04:54 PM
Toddster Member
Posts: 20871 From: Roswell, Georgia Registered: May 2001
The electrical "skin effect" does exist, but it's simply not a significant factor in most automotive electrical systems.
At it's simplest level, "skin effect" is the term applied to the phenomenon that about 2/3 (or, more precisely, 1 - 1/e) of an AC current flowing through a conductor will be found within "skin depth" d of the outer surface of the wire. The depth d is inversely proportional to frequency, and for a copper wire in air can be reduced to a simple empirical formula:
d = 2.6 / sqrt (f)
where:
d = skin depth in inches f = frequency in Hz
Probably the highest current intermittent load on the Fiero electrical system is the ignition, which will have a maximum frequency of about 300 Hz (6000 rpm x 3 ignition events per crankshaft revolution of a V6). At that frequency the skin depth d will be about 0.15 inch ... significantly larger than any single wire used in the Fiero except for the battery and starter cables. Q.E.D.
The real reason for using a flat braided ground strap in an automobile ... or for using stranded wire rather than cheaper solid wire, for that matter ... is its mechanical flexibility.
All accurate. A braided strap is mechanically better than the rest of the wires in the car but that is not the reason for using it in this application. If that were the case, every wire that is tugged when the engine rocks back and forth would need to be braided too. And some of the wires under the hood get a lot more flexing than the ground strap. But I think you have underestimated the "skin effect" (never heard it called that but I am a lowly electrician and not an electrical engineer)
The problem with the electrical system of a Fiero is that over time wire insulation becomes cracked and brittle, wires corrode, and potentials become greater. As loads are required by wires of ever decreasing capacity, a grounding strap has higher and higher demands placed on it. Somebody also mentioned EMI which, in a strict sense, is not really part of the equation since the Fiero braided strap is specifically a grounding strap and not a bonding strap. However, over time the degridation of the wiring in the car will necessitate a bonding requirement for the ground strap by default. When all of this is added up (and to be honest, I haven't done the adding because...well, I don't care. ) I'll bet it's a lot higher than 300 Hz.
But like I said, all this is academic. The bottom line is:
Big Strap Good.
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09:44 PM
Jun 19th, 2007
Marvin McInnis Member
Posts: 11599 From: ~ Kansas City, USA Registered: Apr 2002
Actually, while I knew that the skin effect was dominant at high frequencies I had never realized that it could be significant at even 60 Hz in large conductors and bus bars. The skin depth is about 1/3 inch (8.6 mm) at 60 Hz ... which means that it becomes an important consideration for things like heavy bus bars and long-haul utility power lines.
[This message has been edited by Marvin McInnis (edited 06-21-2007).]
