Iridium Plugs and Gas Mileage

Not true. The vehicle runs off of the battery not the alternator. The alternator just keeps the battery full.
They run off the alternator. The battery is there to act somewhat as a “filter” but most vehicles will happily sit there and run without a battery.

Even if it was true, if you increase the load on the battery the alternator would have to work that much harder to recharge/maintain the battery putting us right back to “increased load=less mpg”
 
They run off the alternator. The battery is there to act somewhat as a “filter” but most vehicles will happily sit there and run without a battery.

Even if it was true, if you increase the load on the battery the alternator would have to work that much harder to recharge/maintain the battery putting us right back to “increased load=less mpg”
No , they run off the battery, the alternator is for replenishment, you are correct about the battery being a filter, but that is for unexpected demands to reduce surges.
 
No , they run off the battery, the alternator is for replenishment, you are correct about the battery being a filter, but that is for unexpected demands to reduce surges.
Removing the battery while the car was running is a shade tree/old school way of testing an alternator. If what you’re saying is true, the car should die the second you disconnect the battery. Most won’t. Here’s a 2000 Accord doing it just fine. It’s not recommended because computers really don’t like voltage spikes like those that occur when you disconnect a battery from a running vehicle.

Some cars yes you are correct. BMW had a system where the alternator really only kicked on during coasting.

 
Removing the battery while the car was running is a shade tree/old school way of testing an alternator. If what you’re saying is true, the car should die the second you disconnect the battery. Most won’t. Here’s a 2000 Accord doing it just fine. It’s not recommended because computers really don’t like voltage spikes like those that occur when you disconnect a battery from a running vehicle.

Some cars yes you are correct. BMW had a system where the alternator really only kicked on during coasting.


You disconnect a battery on a running modern engine you can foul up the ECM and other modules beyond repair, it might operate, but damage will be done. Not the intended or proper order of operation.
 
Not true. The vehicle runs off of the battery not the alternator. The alternator just keeps the battery full.
Ahhhh, and what keeps the battery charged? Batteries are not perpetual energy providers. It's the alternator that provides the electricity power that your vehicle uses. And the alternator is powered by the engine. Increase the electrical load and you increase load the alternator must supply, and that increases the load that the engine must turn, which decreases the miles per gallon.
 
Put an Amp clamp on meter on any vehicles alternator output wire and increase the electrical load my turning on a light of the vehicle and you will see that the alternator output increases as the electric load increases. There is a limit to this and that is how much the alternator can put out at the RPMs that the engine is running at which results in the RPMs that the alternator is turning at. If the alternator cannot keep up because it has hit its limit for the RPMs that the engine is currently turning at, then in that case the battery supplies the power temporarily but then when the engine RPMs become higher or other things are shut off so that the capacity of the alternator is then enough to supply the charge to the battery to make up for the discharge of the battery then the alternator puts that power back into the battery. The end result is that the alternator has to supply the power that was taken from the electric system.

The battery working in combination with the alternator is not a perpetual energy machine, and all power that comes from that combination has to eventually be provided by the alternator which in turn is provided by the engine.
 
No , they run off the battery, the alternator is for replenishment, you are correct about the battery being a filter, but that is for unexpected demands to reduce surges.
The battery is a buffer in many/most cases, especially older vehicles. It only becomes the primary current provider when there is enough load that it pulls down the alternator output to below the battery charged voltage of ~12.9 volts. That is because the alternator charge voltage is higher than the battery voltage. Measure your brake light bulb (or anything else with a normal supposed-12V feed on an older vehicle with engine running, and what do you get? Around 14V. Where is the extra voltage coming from? Not the battery.

In modern vehicles with smart charging systems it is a bit different. Battery is primary power supply until the vehicle selects the right moments for the alternator to energize and charge, to slightly improve fuel economy, such as at no throttle and deceleration events, braking.

If we're going to generalize, it would be fairest to state that they work in parallel.
 
Ahhhh, and what keeps the battery charged? Batteries are not perpetual energy providers. It's the alternator that provides the electricity power that your vehicle uses. And the alternator is powered by the engine. Increase the electrical load and you increase load the alternator must supply, and that increases the load that the engine must turn, which decreases the miles per gallon.

The alternator either puts out 14.5v or it doesn't. It doesn't put out less, unless it's going bad, it doesn't put out more, unless it's going bad.
Alternators are either on or off. The do not "work" harder based on amperage draw.
Yes the alternator takes power from the engine to run, not as much as the aircon or power steering does though.
A more efficient ignition system will draw less power, the coil is going to put out its max voltage, no more, no less. But the less resistance it has to push through the power power that gets to the spark plug.
The less resistance in the spark plug, the stronger the spark. The stronger the spark, the quicker the ignition of the air/fuel mixture, the better and longer the burn before it is pushed out of the exhaust valves.
 
The battery is a buffer in many/most cases, especially older vehicles. It only becomes the primary current provider when there is enough load that it pulls down the alternator output to below the battery charged voltage of ~12.9 volts. That is because the alternator charge voltage is higher than the battery voltage. Measure your brake light bulb (or anything else with a normal supposed-12V feed on an older vehicle with engine running, and what do you get? Around 14V. Where is the extra voltage coming from? Not the battery.

In modern vehicles with smart charging systems it is a bit different. Battery is primary power supply until the vehicle selects the right moments for the alternator to energize and charge, to slightly improve fuel economy, such as at no throttle and deceleration events, braking.

If we're going to generalize, it would be fairest to state that they work in parallel.

The "smart" or variable charging system's vary the voltage they put out, "dumb" alternators are either on or off, meaning charging at 14.5v or not charging at all.
The variable alternators charge at 15+v and as low as 12v. They vary the output based on demand.
 
The alternator is the primary electrical source when the engine is running. Basic electricity. Higher voltage source, or electrical “push” on a parallel circuit (14V+ when running) vs 12.6 (nominal battery voltage) will take precedence. The battery is there for electrical back up when electrical demand is at its peak or alternator cannot supply enough current for load. Or else how do you think the alternator will charge the battery if the voltage output is the same as nominal battery voltage? The answer is it won’t.

As to the OP, just stick with the motorcraft OE plugs. I’d be surprised if you would be able to see a measurable difference in fuel economy.
 
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The alternator either puts out 14.5v or it doesn't. It doesn't put out less, unless it's going bad, it doesn't put out more, unless it's going bad.
Alternators are either on or off. The do not "work" harder based on amperage draw.

I disagree with this. If the *battery* is at 14.5 volts, and the alternator is putting out 14.5 volts, no amperage feeds into the battery. At this point, there are only friction loads on the engine, from spinning the alternator.

But when all electric loads are maxed out, the alternator will, obviously, feed amperage back into the system. *And it will take more energy from the engine to do this.*

If the alternator is generating a kilowatt, the alternator will absorb at least 1.34 hp from the engine (friction drag will be higher, too). So MPG will drop somewhat.
 
The alternator either puts out 14.5v or it doesn't. It doesn't put out less, unless it's going bad, it doesn't put out more, unless it's going bad.
Alternators are either on or off. The do not "work" harder based on amperage draw.
I haven't seen a poster this repeatedly, aggressively wrong in quite a while.

Alternators absolutely have a middle ground, between on and off, and they spend most of their time there.

The only exception is at idle with the high beams, blower, rear defroster etc on when they are full fielded. You get a voltage drop until the battery starts helping with all the loads.

If you don't believe me, go take the serpentine belt off your engine. Spin the alternator pulley by hand. Now turn the ignition on, so it's trying to charge. Spin that pulley again.
 
If you don't believe me, go take the serpentine belt off your engine. Spin the alternator pulley by hand. Now turn the ignition on, so it's trying to charge. Spin that pulley again.
Yup, back EMF is a real thing. More energy will be required to turn the alternator when it's under load.
 
Assuming this is a true story, it wasn’t due to the plugs.

Utter nonsense.
l would think the factory coils would provide all the needed secondary system voltage required.
Put that system on an ignition scope, and pull a plug wire off at the plug, the voltage trace will spike off the screen.
 
Somewhat off topic, but what do you guys think of just using old fashioned copper spark plugs in a 2001 Grand Prix, with a 3.1 L motor?
I am not worried about the plugs lasting 60,000 or 100,000 miles, I'm lucky if I put 2,000 miles on a year.
 
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