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.

Reply to
Existential Angst
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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.

Reply to
spamTHISbrp

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

Reply to
Richard

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. :)

Reply to
Richard

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.

Reply to
AMuzi

BTW, this is the sticker I have on the battery panel of my boat.

It is there so we can tell how much charge remains in the battery. Multiply the percentage by the current rating of the battery to determine remaining amp hours. (Do not use the cold cranking amps rating tho)

Under normal circumstances I never let it go below 60%. I was still using one of the original (20 years old?) AGM group 27 batteries until last year. It would still charge up to 12.45 volts. It didn't get charged for many months during the move, and I have to replace it now.

Another aside, let the battery set without the charger for 24 hours before taking the reading if you want to know the actual battery condition as far as life remaing.

12.60+ 100% green 12.50 90 12.42 80 12.32 70 12.20 60

12.06 50 yellow

11.90 40

11.75 30 red

11.58 20 11.31 10 10.50 0
Reply to
Richard

"Existential Angst" wrote in news:50781447$0$9795$ snipped-for-privacy@cv.net:

You'd be better off to re-examine this with a few months of mileage/fillup recordings, both with the alternator working and with it not (and by that, I mean removal of the drive belt). This sort of statistical analysis is /very much/ dependent on sample size and consistency of data recording, so you need to be very precise.

Your basic thesis is not unreasonable: Honda has, for years now, been regulating its alternator charging using a device known as an Electrical Load Detector. The ELD lessens engine load by reducing alternator output unless there is high demand. However, the ELD is a US-only device, meant to boost Honda's CAFE ratings, not to boost fuel consumption as observed by the owner; its effects are unlikely to include anywhere near a 15% increase in gas mileage.

Have you done the arithmetic?

Suppose you normally get 25mpg; disconnection of the alternator brings you up 15%, or to 28.75mpg. Assuming you drive 12K miles per year, you'd save, assuming $3.75/gal, about $263 per year.

If you mean to run your battery down regularly as you drive (like in the days of the Model-T), then you need a marine/deep-cycle type that will survive repeated dips into low-charge territory. These go from between $140 to $400.

Reply to
Tegger

You would need to disconnect the LITTLE wire drom the alternator, not the big one - and it would throw a code on the engine control computer and possibly put it into a limp mode - not saying it would, but it could. Your alternator takes as much power as the loads connected to it - so fuel pump, ignition, injection, lights and heater fan if used, as well as cooling fan if it is electric. Mabee 600 watts on a cold night, and 50 or 100 on a mild day. Thats less than 1 HP. After starting the alternator needs to recharge the battery as well, so another 1000 watts for a couple of minutes, tapering down to nothing - say another HP for 5 minutes.

If you are going to save 15% on fuel consumption you would have to be able to drive on about 6 HP average without the alternator.

Not going to happen, methinks .

Reply to
clare

etc. being done internally.

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.

Reply to
clare

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.

Reply to
clare

You may have only a single connection to the alternator which goes straight to the battery of to the battery via a connection on the starter. The reason is that the internal alternator regulator receives power from the battery via the main power cable.

If this is the case then in order to externally control the alternator you would need to cut into the regulator and jury rig some sort of external connection which would likely end up in bypassing the regulator.

This certainly is possible - I have done it with two alternators for marine use in order to use external regulators, however whether it is logical for an automobile can be argued.

If you have, say a 100 amp alternator, then: 100 amps x 14 volts =

1,400 watts = 1.8 Hp. But the alternator is driven at a higher speed then the crankshaft so there is additional H.P loss due to the over-driving plus belt friction. For guessing purposes say 100% losses so Required H.P. then is 3.6 HP.

You then need to estimate the average amount of H.P. required by your driving style and compute required alternator power as a percentage.

Back in my days of unofficial, Sunday afternoon, drag racing it was common knowledge that disconnecting the alternator (and the fan) would result in a faster car.

Reply to
John B.

Nope. A magneto is self contained and requires no outside source of power.

Reply to
John B.

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.

Reply to
Michael A. Terrell

At steady-state, middling-speed cruise that's actually plausible. It's when you need to accelerate smartly that you actually use all the horsepower of your engine; at cruise it's only using a very small fraction of available power. Below speeds where aerodynamic drag becomes a significant factor, I would expect power consumption to be in just about that range.

I mean, I can ride a bicycle at 30+ MPH, and I doubt I put out even one horsepower :)

nate

Reply to
Nate Nagel

John B. fired this volley in news: snipped-for-privacy@4ax.com:

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

Reply to
Lloyd E. Sponenburgh

Did I say electrical power???? No. It takes ENGINE power to run a Magneto The faster you run it the more power it absorbs - just like an old generator or an alternator or Dynamo. It is basically just like a Kettering ignition with it's own generator, all built into a nasty little case.

Reply to
clare

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.

Reply to
John B.

I built an electric powered Fiat several decades ago. Very light car, with good aerodynamics. 6 HP would move me along at about 9 or 10 MPH. IIRC 10 HP would move me at 30MPH. Accellerating TO 30MPH in any reasonable time took significantly more. Something like 30HP to keep up with normal traffic away from a stop on a slight uphill grade.

Reply to
clare

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.

Reply to
John B.

The 1970's GM HEI module:

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Reply to
Jim Wilkins

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