Disabling the alternator on a car

Awl --
Would seem like a no-brainer, but goddamm, it shore has me beat!
Yeah, I know, pull the fuse!! Yeah, I know, the fuse labeled
"alternator"..... :) :)
But when I did that, the alternator light or battery lite would not come on. AND, iirc, I DID check the voltage at the battery, to see if it went down to 12, or was up at the ususal 13-14, and indeed, it stayed at 13-14, indicating a working alternator.
And the engine compartment is so g-d crowded/complicated, I can hardly tell a wire from a hydraulic line, so it's not easy to even find the right wire. I figger at 100 A, the wire would have to be perty thick....
The reason for disconnecting the alternator is this: On an old mazda 929S, the alternator went -- and I could StoG that my mpg jumped by 15%.... would like to re-examine this phenom with my ScanGauge, to see if it is real.
If this is indeed a true phenom, I could wangle myself a bit of a hybrid by just keeping a spare batt in the car, and switch in the alternator when the first batt dies. But basically try to do all the batt. charging at home.
Altho, there proly is no free lunch: I'll proly use my gas savings to buy a new battery every year?? LOL But the actual tradeoff would be inneresting to see.
--
EA




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On Friday, October 12, 2012 8:59:52 AM UTC-4, Existential Angst wrote:

Many alternators connect with just one wire nowadays, all the field regulation etc. being done internally.
Disconnecting that one wire might damage the alternator while the engine is running, probably since there are no permanent magnets in it disconnecting with the engine stopped may/might/probably be safe.
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On Fri, 12 Oct 2012 06:46:35 -0700 (PDT), snipped-for-privacy@yahoo.com wrote:

running, probably since there are no permanent magnets in it disconnecting with the engine stopped may/might/probably be safe. Virtually EVERY current alternator still has an external field connection of some sort - but many can NOT be shut off by simply disconnecting them. Any with the regulator built into the engine control computer can be shut down by disconnecting the field wire.Any with an external regulator (rare animals today) can also be shut down by disconnecting the wire, while less than half, I would guess, of internally regulated alternators can be shut off by disconnecting the control wire. Disconnecting with the engine shut off will prevent SOME of those from starting to charge.
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On Friday, October 12, 2012 9:39:51 PM UTC-4, Clare wrote:

running, probably since there are no permanent magnets in it disconnecting with the engine stopped may/might/probably be safe.

Wrong, many have exactly one wire.
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On Mon, 15 Oct 2012 06:44:45 -0700 (PDT), snipped-for-privacy@yahoo.com wrote:

running, probably since there are no permanent magnets in it disconnecting with the engine stopped may/might/probably be safe.

Give me a list of five models that use a single wire alternator from the factory. Any less than 5 is not "many".And if all 5 models are from one manufacturer it still doesn't count.
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On Monday, October 15, 2012 11:58:24 AM UTC-4, Clare wrote:

is running, probably since there are no permanent magnets in it disconnecting with the engine stopped may/might/probably be safe.

Yeah, I'll get right on that.
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On Tue, 16 Oct 2012 06:23:24 -0700 (PDT), snipped-for-privacy@yahoo.com wrote:

Tell you what. I'll make it easy for you. Give me TWO from different manufacturers.
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On 10/12/2012 6:46 AM, snipped-for-privacy@yahoo.com wrote:

running, probably since there are no permanent magnets in it disconnecting with the engine stopped may/might/probably be safe.
If you're bent on doing this experiment... Measure the peak battery voltage fully charged while charging. Decide how low you want your battery to discharge. Subtract the two numbers and put enough diodes in series to make it happen. That's a fail-safe that keeps you going. The diodes won't cost you any power when not charging. Probably have to do something about powering the field with only one wire so the alternator can start up. Maybe some reverse diodes or a resistor.
Just spinning an alternator takes energy. I once tried to build a 120VDC generator from a lawnmower engine and an alternator. Took all the engine power just to spin it up under no load.
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running, probably since there are no permanent magnets in it disconnecting with the engine stopped may/might/probably be safe.

Then you were definitely doing something wrong. The drag of 2 ball bearings and a pair of 1/4 inch brushes and a 4" low performance cooling fan is pretty negligible - even for a 2 or 3 HP lawnmower engine.
Under load would be a different story. 6 HP will give you ABOUT 30 amps running at 3600 RPM set up to give 120 volts DC. Used to run 120DC alternator kits on my Dad's old Dodge work trucks for running drills and saws roughing in houses (he was an electrician)
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On 10/12/2012 7:59 AM, Existential Angst wrote:

15% seems a bit high for a high MPG car, but maybe.
The alternator does take a considerable amount of power to turn.
But I'm afraid that the
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On 10/12/2012 12:10 PM, Richard wrote:

Sorry - hit the wrong button.
Without the alternator your battery will not run the car for very long at all. Solid state ignition takes power.
And you will not get much life from the battery either if you pull it much below 50% very often.
What you want is a magneto. :)
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On 10/12/2012 12:13 PM, Richard wrote:

We bicyclists agree, assuming that will pretty much f**k up the damned telephone. Hopefully, the driver could start to pay attention, at least to some small degree.
--
Andrew Muzi
<www.yellowjersey.org/>
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wrote:

Or like on an airplane - TWO magnetos. Then you still need to power the injection - which takes more power than the ignition. And wait - a magneto IS really just an alternator or generator - and it takes power as well.
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On Fri, 12 Oct 2012 21:42:13 -0400, snipped-for-privacy@snyder.on.ca wrote:

Nope. A magneto is self contained and requires no outside source of power.
--
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John B.
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"John B." wrote:

BS. It would have to be 'Perpetual Motion' if you were correct. They are permanent magnet and convert motion to electricity, until the magnet fails.
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On Sat, 13 Oct 2012 07:42:55 -0400, "Michael A. Terrell"

You apparently didn't read the portion of the post I was replying to, where the guy says: "Then you still need to power the injection - which takes more power than the ignition. And wait - a magneto IS really just an alternator or generator - and it takes power as well."
So no, in the context used it a magneto requires no outside source of (electrical) power.
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Where did you get that interesting piece of information? Do they have batteries in them that finally just wear out, and you throw the whole thing away when they do? I guess that will get (even more) expensive on all those old Lycoming and Continental engines out there with their magneto batteries about to run down...
Or... Just keeping in mind the old "conservation of energy" crap they stuck us with in school (and never gave us a good alternative to), did you maybe mean that magnetos DO require "power" to create a spark, but that they require no outside source of ELECTRICAL power?
Byda... how do you get the computer to control precisely (and rapidly) where the cam on the ignition rotor shaft is, in order to change the timing on magnetos?
LLoyd
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On Sat, 13 Oct 2012 07:40:27 -0500, "Lloyd E. Sponenburgh"

You have adroitly clipped the part of the post I was responding to.
"the injection - which takes more power than the ignition. And wait - a magneto IS really just an alternator or generator - and it takes power as well."
Which seems to imply that the magneto requires a source of electrical power... which I responded to, saying "No it doesn't.".
If you wanted to precisely control the ignition timing using a computer it would probably be simpler to use a "low tension magneto" where the magneto is a relatively low voltage generator and a secondary coil steps the voltage up to that necessary to fire the plugs. the low voltage stuff can then be electronically controlled although I have only seen this done on a gas fueled, lean burn, stationary engine.
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The 1970's GM HEI module:
http://www.rustpuppy.org/ignition/HEIschematic.gif
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On Sat, 13 Oct 2012 10:58:59 -0400, "Jim Wilkins"

Which has a "retard start" but does not controll timing across the RPM band. IIRC it retards the timing 10 degrees for starting. The retard was triggered by grounding the "R" pin - which was only on SOME of the GM modules (called EMR if I remeber correctly). The standard 990 4 pin module did not control the timing. There was another 4 pin variant that automatically retarded the timing, I believe, 4 degrees on start. These were used in distributors WITH mechanical advance. CCC didtributors with no built in advance required full computer control.
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