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Old 12-28-2010, 12:16 AM   #1 (permalink)
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alternator efficiency

ok so ive been reading up on alternator deletes and stuff like that.
i have decided my next mod will be the alternator, now my alternator is 28 years old so efficiency is probly not the best in the world, i was thinking of finding a more efficient alternator to start with.

i was going to seek a full aftermarket one made to spec and trial that and then install the disengager to test differences.

my question is: would it be worth getting another alternator and if so is their any special new types out there (brushless design or something help me out)

all ideas and theories welcome. the more input the better

money isnt a problem for me im in this game for getting better milage and testing purposes. not saving money

heres a start
Eco Tech Alternators - Ecoair Corp. - high output alternator, high amp alternators

Alternator - Wikipedia, the free encyclopedia

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Old 12-28-2010, 01:05 AM   #2 (permalink)
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To start with what type of alternator do you have at the moment?
is it the standard type which has brushes and a rotating field winding?

regarding efficiency even though your alternator is fairly old you may not get much better efficiency out of a new one unless your current alternator is damaged some how. Its likely something like 60% efficient at the moment.

The ideally efficient alternator for you would have the following features
- permanent magnets for the rotating field as this will not require brushes and energy to energize the field winding
- low loss diodes schotcky diodes which have low voltage drop
- Some method to disable the alternator charging the battery such as field disabling, a clutch to stop the shaft rotating or a relay to disconnect the output for the alternator.
- no fan fins on the rotor, there are usually fan fins on both ends of the alternator, this takes up energy from the drive train but it cools the alternator.

I am not sure the ideal alternator exists but maybe you will be able to modify something that is out there.

good luck
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Old 12-28-2010, 01:23 AM   #3 (permalink)
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Thanks for the link, I've never heard of these alternators.
But, the Eco-Tech appears to be overkill for a car. The size would be difficult to manage, and at 38 pounds it is much heavier than any automotive alternator. If I were to adapt a new alternator, it would be a General motors CS130. It weighs 10 pounds, and the minimum output (depending on model) is 100 amps, more than your stock alternator.
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Old 12-28-2010, 04:15 AM   #4 (permalink)
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Quote:
Originally Posted by Ang84Indy View Post
Thanks for the link, I've never heard of these alternators.
But, the Eco-Tech appears to be overkill for a car. The size would be difficult to manage, and at 38 pounds it is much heavier than any automotive alternator. If I were to adapt a new alternator, it would be a General motors CS130. It weighs 10 pounds, and the minimum output (depending on model) is 100 amps, more than your stock alternator.

yeah that website was an example...

and saand:
mine is a 45amp brush one with steel cooling fans connected to the belt drive. so there is room for improvement.

remember 10 mods netting 1.5% better fuel economy each all add up in the end .

this is my new project for next year im going to make a decent alternator

if you changed your alternator to one that is a higher amperage will it have to run less often or will it be about the same??
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Old 12-28-2010, 06:35 AM   #5 (permalink)
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I found the following info in Press information on PSA's e-HDi:
Quote:
The StARS starter alternator is a synchronous machine using three-phase current. The rectification of the alternator current to battery current (AC/DC) is realized with so-called field-effect transistors instead of diodes, which gives an excellent efficiency at >77% (VDA measurement), or 10 points higher than a traditional alternator and thus allows additional fuel savings, independently from the engine stop phases.
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Old 12-28-2010, 09:28 PM   #6 (permalink)
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An alternator supplies power based on the demands of your car's electrical system. So a higher capacity alternator will run at a reduced capacity more often than your stock one will. This is good for longevity of the alternator, and you have extra capacity when you need it.
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Old 12-28-2010, 09:59 PM   #7 (permalink)
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Quote:
Originally Posted by saand View Post
- permanent magnets for the rotating field as this will not require brushes and energy to energize the field winding
Not sure how this is supposed to be ideal. How are you going to have the alternator respond to voltage transients, if your rotor is a magnet?
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Old 12-29-2010, 02:51 AM   #8 (permalink)
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modern day alternators have brushless designs. i wonder if you can swap alternators over or am i going to have to do some "modifications" to make it fit
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Old 12-29-2010, 07:18 AM   #9 (permalink)
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I suspect with almost any non stock change you are likely to need to make some brackets to make it fit right.

t Vago Sorry i should have explained the permanent magnets more. Standard alternators adjust the field to change the amount of energy that the alternator generates. A permanent magnet alternator would not be able to do this. To adjust the rate of battery charging it would instead electronically "chop" the output of the 3 phase coming from the alternator and generate a variable output power from the alternator.

pounsfos i like your ambition to make a better alternator maybe others will benefit from your work on it as well. I would expect this will be quite a hard modification so if your after just high mpg i hope this is at the end of your list of mods.
Also regarding your question on the amperage of the alternator, if you have a higher current alternator its likely to run at exactly the same rate as a higher amperage alternator (when your up at a rating or 45 amps). The alternator will produce a voltage of say 15v, the battery will be charged up to an extent. The battery will take whatever charge it wants at the voltage given. If the alternator is unable to supply that charge it will either get damaged or it will reduce the voltage output.

If your designing your new alternator you probably want to design it to suite the maximum working load of the car so whatever the car will take from the battery when the head lights are on, the radio, wind screen wipers, power windows ...
add that all up and the size your alternator to generate at least that amount.
anything else will just increase the rate at which you charge up your battery. So it make give you some ability to take away energy when breaking but i have found with my setup i don't really break all that much, i am typically only having the alternator charge when i am in neutral.
Also you can only force so much current into your battery until it starts cooking. if you put more than 15v on the battery to try to force more current in it will just start to get damaged. Note: electric cars are more able to regeneratively break due to the high voltages and large battery packs.
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Old 12-29-2010, 07:46 AM   #10 (permalink)
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very nice right up saand.
luckily all my battery/alternator needs to power is my radio,engine and my windscreen wipers/squirters. everything else is manual i dont use my heaters. the only heater i need is my good old
"harden up" pill. works everytime.

i am picking up my amp gauge to start testing loads (anyone want to take a guess at my load).

after this i will start sourcing parts and advice as to where to go.

toyota are very good at using same mounting points through various models. i needed a new dash cluster for my starlet (so i have a rev gauge instead of having to buy a tacho) and i got one out of a 1997 toyota supra. instant fit lol

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