Interesting , the average standard 6 cyl. starter motor is 1HP , not sure how that all equates to a thermo. fan motor rating , they must be
pretty good little motors to pull around 60 amps ?, dunno.
Posted 06 May 2017 - 06:01 PM
Interesting , the average standard 6 cyl. starter motor is 1HP , not sure how that all equates to a thermo. fan motor rating , they must be
pretty good little motors to pull around 60 amps ?, dunno.
Posted 07 May 2017 - 09:52 AM
Posted 07 May 2017 - 09:55 AM
Posted 07 May 2017 - 09:56 AM
My understanding of power generation is rudimentary at best, but the alternator does not provide power to the accessories (fans, radio etc), they are fed from the battery. The alternators role is to keep the voltage and charge in the battery the same. Hence why you can run fans, radio etc while the engine is off.
This would mean by my reasoning that the alternator is never working more or less at any given time but at a constant rate.
That's what I thought too.
s
Posted 07 May 2017 - 11:10 AM
Posted 07 May 2017 - 11:43 AM
Posted 07 May 2017 - 11:50 AM
I don't think the pulley on the alternator gets harder to rotate as draw demands increase hence the effort required by the engine to turn it remains constant
I've always thought they were like the generator you had on your bike tyres to run the headlight on the handlebars, the faster the engine cranks the more power is pushed out, not the harder the alternator works the more it drains from the engine.
s
Posted 07 May 2017 - 12:11 PM
I've always thought they were like the generator you had on your bike tyres to run the headlight on the handlebars, the faster the engine cranks the more power is pushed out, not the harder the alternator works the more it drains from the engine.
s
Posted 07 May 2017 - 04:52 PM
You guys are thinking Generators. GM fased them out in the late 60's.
Our cars run Alternators, they DEFINITELY do NOT provide the same power regardless.
More load off the battery, the alternator puts in more power to replenish it, and as such puts more load on the engine. An alternator spinning on an engine with nothing attached to it will only draw the power required to spin the fan and bearings. A generator will draw the power required to produce whatever it is rated to.
"The brushes in an alternator carry only excitation current, a small fraction of the current carried by the brushes of a DC generator,"
https://en.wikipedia...iki/Alternator_(automotive)
Edited by Bomber Watson, 07 May 2017 - 04:53 PM.
Posted 07 May 2017 - 05:12 PM
You guys are thinking Generators. GM phased them out in the late 60's.
I thought it was later than that or am I thinking of a primitive alternator? I recall an older style alternator that had a separate module whereas the Torana alternators have that inbuilt.
s
Edited by StephenSLR, 07 May 2017 - 05:13 PM.
Posted 07 May 2017 - 06:23 PM
Different beasts.
Early alternators had a separate module.
Posted 07 May 2017 - 07:03 PM
Alternators generate 3 phase AC which is then rectified to produce DC and are regulated by excitation by the regulator.
Generators produce DC which was regulated by a fairly "crude complex" system of relays.Three phase is far more better for anything
from generation of lectrickery to running motors.
Any load connected to either system will result in some sort of power being sucked out of the engine , thermo. fans . seem to be quite efficient other wise they would not be used.
As far as a couple of thermos. drawing 2HP goes ? , equates to 2 stock 6 cyl. starter motors driving a fan each , them little motors not much bigger than a wiper motor must be bloody good gear or something is not right and the drain is not what we are being told ?
Just try testing an alternator on the bench and see how much it takes to hold the thing in place with next to no load.
Posted 07 May 2017 - 07:13 PM
as above....
Heres my take on it,
Talking Thermo fan load only,not all the others stuff
My LJ has one thermo fan, pulls around 30 amps.
30 x 13 = 390 watts.
If we assume some poor efficiency like 50%..then it would take appx 800 watts input to the alternator to make the 390w output.
Allow for some alternator windage/alt fan and bearing drag,or whatever, lets say 1000w input power is reqd. to make it happen.
1000w = 1kw = 1.34Hp
Seems light on, but thats how it seems to be . I guess back in the day they always said an engine fan was about 7hp..........7 versus 1.3...we have a winner?
Edited by RallyRed, 07 May 2017 - 07:14 PM.
Posted 07 May 2017 - 09:10 PM
Posted 07 May 2017 - 10:05 PM
when i had my 200amp alternator at my auto lec being tested he had it mounted and connected to a huge 240v motor to spin it up,
as i had a gilmer pulley on it at that stage and he had a vbelt set up, he just ran the vbelt over the gilmer to test it,
as the output started to climb the belt would start slipping, could only test it up to around 100amps ,
my point is that a alternator does get harder to turn the more it has to output,
Posted 08 May 2017 - 08:36 AM
yep, that's that old thing that Newton ( not Bert) figured out...."when one object exerts a force on a second object, the second object exerts an equal-and-opposite force on the first object.."... or in our language....""listen up.....if you push me to make 200 amps, well, I'll push back with the same amount of force""
..or something like that...lol
Posted 08 May 2017 - 09:55 AM
About time this thread dispelled some myths. Completely agree with all Bomber has said, particularity where alternators will vary the the load to suit (current/power)demand. Thermo fans WILL save HP when they are NOT on. They are not needed MOST of the time, so you save HP most of the time. When they are on, you normally don't need 100% of the HP available. EG Slow speed, stop start, idling.
Thermo fans do not switch off at high speed unless your car is ECM controlled and has that functionality built in. They are normally only coolant temperature controlled.
If you are building a burnout car then a big mechanical fan makes sense.
I am a bit surprised that the clutch fan taxed so much HP when cold. I wonder if the HP taxed would be less if the test was done with say 60km/h airflow to the radiator to simulate real world conditions. I suspect it would be reduced. because it's less work to spin a fan into a head wind than in still air.
Posted 08 May 2017 - 10:01 AM
Thermo fans do not switch off at high speed unless your car is ECM controlled and has that functionality built in. They are normally only coolant temperature controlled.
In my car, I can see my temp. gauge needle dropping at high speed which I guess means the coolant temp is going down. For me high speed is limited to driving on the highways. Ymmv if you have a drag car I guess.
s
Edited by StephenSLR, 08 May 2017 - 10:02 AM.
Posted 08 May 2017 - 10:30 AM
Thermo fans WILL save HP when they are NOT on. They are not needed MOST of the time, so you save HP most of the time.
As I earlier mentioned- my tests indicated any HP savings are negligible (when turning thermos off compared to on). However, that does not mean there are not HP savings, just that its like measuring a bees dick with a tape measure. 1hp will never be felt by seat of the pants, and its even not enough to really be picked up accurately by a dyno or drag strip.
Alternators will create extra resistance when the electrical load is increased- I've never disputed that... its a known fact, and something I have observed... However, over the years I have heard so many people tell me that I should be turning the thermos off as they will drain HP etc due to greater load on alternator and so forth- which was why I tested at the strip... again, the hp drain would be approx 1hp which is negligible. Needless to say, I just run them full time now (no mechanical fan). I could understand 1hp being more significant in a 30hp donk but in 250hp-400hp donks like typical torana engines, its just not enough loss to even think about.
Edited by LC-GTR-1969, 08 May 2017 - 10:31 AM.
Posted 08 May 2017 - 12:00 PM
, the strange thing is that most water pumps these days are still engine driven , not saying the
lectric ones don't work , just saying , engine speed /water pressure in sympathy with engine speed ?
Just picking up on this, I think it not only comes down to economics, but also, with the sophistication and demand on today's electronics in cars it may be a very powerful electric motor to drive for little gain for modern cars, in saying that, coolant speed needs to be linear with engine/coolant temp, not engine speed as such.
You will notice high end stuff comes with a speed controller which senses engine temp, doing away with the need for a thermostat.
Posted 08 May 2017 - 12:32 PM
Edited by Axewound, 08 May 2017 - 12:38 PM.
Posted 07 May 2021 - 11:02 PM
Posted 08 May 2021 - 12:11 AM
Oh shit wait till Byron sees this thread
Posted 08 May 2021 - 12:16 AM
Good to see you are getting around Bruce
you will fit right in here
Posted 08 May 2021 - 01:04 AM
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