spark plugs electrode question

[serge_saati]

On Ford V6 engine, one engine side has spark plugs with center platinum electrode, the other side with platinum on ground electrode. Which side of the engine has the platinum on the center electrode. Front or rear?

[old_master]

All of the plugs should be the same. Sounds like the last guy did half of a tune up

[serge_saati]

In front I have AGSF-32PM (white dot) and at rear I have AGSF-32PGM (green dot). Both platinum.

Here's the explanation I've found in another thread about Taurus 2000:

This is the case for engines employing the "coil-pack" or waste spark
ignition systems. In it the coil fires two spark plugs at once; one on
the compression stroke and the other on a cylinder 360 deg out of phase
(on its exhaust stroke). The current flow (conceptually) goes from the
high-tension lead to the center electrode on one cylinder, across the
gap, to the ground strap through the engine structure to the ground
strap on the cylinder 360 away, across that gap, and finally returns to
the coil pack. Because the current flow is always in one direction, the
platinum only needs to be on the plug electrode that erodes the most. By
arranging the coil wiring appropriately one bank can have platinum on
the center electrode while the other bank has platinum on the ground
strap side. This saves a lot of money in the cost of platinum. One might
think that having to jump two gaps will significantly sacrifice ignition
energy. It doesn't because the properties of the burnt gases in the
waste spark cylinder are very easy to ionize with very low energy losses.

In the field, to avoid confusion on which bank should have the platinum
electrode, aftermarket plugs simply have platinum on both electrodes.
These are commonly call double-platinum plugs.

[old_master]

When the spark leaves the coil, it jumps the plug gap and is grounded. It cannot return to the coil. Both electrodes on the plug burn during firing. Their theory doesn't hold water. In the last paragraph they try to "come clean" by telling you to use double platinum plugs. The cost savings comes from using half as many coils to fire the plugs, not by using less platinum.

Install Autolite APP103 (PP=double platinum) plugs with a gap of .044" and you'll be good to go.

Where did you find that article? I'd like to read it.

[serge_saati]

No, they're right about that. On EDIS, plug fires at end of compression cycle (at TDC) and at end of exhaust on opposite plugs (to burn unburned fuel and reduce emission).

I've also read in another forum that patinum should be on area where electron is received. So on the positive electrode. It's why ford/mercury/Lincoln put different plugs at rear.

I wanted to buy autolite double platinum. But I didn't wanted to pay 66$ for plugs.
So I use the simple platinum (center platinum) that the auto part seller give me. Next time, I'll buy from Ford.

[serge_saati]

Yes, it jumps the plug and is grounded. Then another spark passes through the ground (engine block), jump from the the ground electrode of other plug and come back to the center electrode of this plug. And return to the coil.

[old_master]

I agree, when the coil fires one cylinder on the compression stroke, it also fires a second cylinder on the exhaust stroke. The cylinder that is firing on the exhaust stroke is during the valve overlap period just before TDC, but because the pressures are so low and the charge is diluted by the exhaust gases, no ignition occurs, (the spark is "wasted"). This is why EDIS is referred to as a "wasted spark" ignition system. Both plugs fire at the same time through a common coil pack and both sparks ground out at their respective plugs, (your schematic drawing in post #6 shows it). The spark does not travel back to the coil. Try a Google search for a more technical explanation.

[shorod]

They don't display the dots on the coils to be able to confirm the secondary "polarity" but if one were to assume that the dots are on the top of the auto transformers, cylinders 1, 2 and 3 would have the positive induced pulse and coils 4, 5, and 6 would be the return plugs. Now, the confusing part is electrons (current) would actually flow from negative to positive, so that would suggest if what you pasted in post #3 above is accurate, the platinum center electrode plugs should be 4, 5, and 6 and the platinum ground strap should be 1, 2, and 3.

-Rod

[serge_saati]

Originally Posted by old_master

I agree, when the coil fires one cylinder on the compression stroke, it also fires a second cylinder on the exhaust stroke. The cylinder that is firing on the exhaust stroke is during the valve overlap period just before TDC, but because the pressures are so low and the charge is diluted by the exhaust gases, no ignition occurs, (the spark is "wasted"). This is why EDIS is referred to as a "wasted spark" ignition system. Both plugs fire at the same time through a common coil pack and both sparks ground out at their respective plugs, (your schematic drawing in post #6 shows it). The spark does not travel back to the coil. Try a Google search for a more technical explanation.

Yes it travels, but is not used. It's why is called waste spark. Electron always come back to its source. Same as fluid in hydraulic system. Exhaust gazes doesn't block spark travel.

It's why in some GMs, air is added to exhaust to burn burn residual fuel vapor.

But important point in my thread is that polarity is different from rear to the front of engine. Polarity doesn't change in Ford EDIS. So if electrons go from plug 1 to GND when cylinder 1 is firing, it'll go from GND to plug 5 when cylinder 5 is fired. It's why I was concerned about platinum location on front vs rear plug.

[serge_saati]

Originally Posted by shorod

They don't display the dots on the coils to be able to confirm the secondary "polarity" but if one were to assume that the dots are on the top of the auto transformers, cylinders 1, 2 and 3 would have the positive induced pulse and coils 4, 5, and 6 would be the return plugs. Now, the confusing part is electrons (current) would actually flow from negative to positive, so that would suggest if what you pasted in post #3 above is accurate, the platinum center electrode plugs should be 4, 5, and 6 and the platinum ground strap should be 1, 2, and 3.

-Rod

The bid dots (white and green) I talked about were on the top terminal of the plugs. Thanks, your info on polarity resolves my issues. But it's the opposite, center electrode plugs should be 1, 2, and 3 and the platinum ground strap should be 4, 5, and 6. Cause like I said, patinum should be on area where electron is received/hits.

[old_master]

When #1 fires on compression it needs platinum on the center electrode and #5 needs it on the ground electrode? What about when #5 fires on compression? Plug polarity does not change. When the spark jumps the gap to ground, it's done! Guys, look at the schematic: 1 & 5 fire together, simultaneously. Same goes for 2 & 6 and 3 & 4. The system was designed to be CHEAP. No ignition module, 3 coils fired by the ECM, one tone ring on the crankshaft, one crankshaft position sensor, and no camshaft position sensor = CHEAP! The only thing expensive about this system is the coils wear out / burn out twice as fast.

[serge_saati]

Actually, there's a camshaft position sensor to synchronize the fuel injectors.

I agree, it's cheap.

[shorod]

Originally Posted by serge_saati

The bid dots (white and green) I talked about were on the top terminal of the plugs.

Right, but I'm referring to the "dot" on the transformer primary and secondary windings which identify polarity/phase of the respective transformer windings. Completely separate from the dots on the spark plugs.

Originally Posted by serge_saati

But it's the opposite, center electrode plugs should be 1, 2, and 3 and the platinum ground strap should be 4, 5, and 6. Cause like I said, patinum should be on area where electron is received/hits.

I don't see where you mentioned that the platinum would be on the area where the electron is received. The info you pasted mentioned it's where the electrode erodes the most. I'd expect the electrode that sources the spark (arc) would erode the most, but that's just a guess. If you've read that it's the electrode that "receives" the electron, then you're correct and what I suggested in post #8 is backward.

-Rod

[old_master]

Just an FYI on the paint on the plugs.... When the engine is assembled, they put a dab of paint on the plugs so if there's a warranty issue, the factory can tell if it was an original plug or a replacement, (the factory will "call back" certain parts when there's a warranty claim). As an added bouns, the technician can tell at a glance if the engine has been tuned since it was built.

[plymouthsrock]

Good post here.

Some empirical data: I ran into this when I tuned my 99 Taurus "U", the front bank plugs had twice the gap (erosion) as the rear bank. I thought "why would they not change the front bank plugs?", but this could explain it.