16 volts at idle!
08-31-2016, 09:27 PM
#21
Originally Posted by MN_V
I know - I meant suggesting it was because of the smaller pulley. Larger or smaller is no different than different RPMs from the engine changing the alternator speed.
The alternator creates AC votage that the rectifier/regulator converts to DC.
The alternator creates AC votage that the rectifier/regulator converts to DC.
If over excite the alternator, the regulator cannot keep up and you end up over your nominal voltage.
I had a situation where i used a 25% up crank pulley so to keep my amps and voltage up i used esp's small pulley. It was about 1.5-2" in dia and since i installed it i had nothing but 16+ volts all the time.
I couldnt tune the car for i was either.
If you dont believe me, try it and find out first hand...
09-01-2016, 06:50 AM
#22
Then why don't all of our cars start producing 16V when the engines are spooled up at higher rpms? That has a much greater effect on alternator speed than a smaller pulley does at idle speed. You can believe you're right, but again the OP has shown if someone had followed your advice, he'd be chasing his tail to no avail.
09-01-2016, 11:21 AM
#24
Then why don't all of our cars start producing 16V when the engines are spooled up at higher rpms? That has a much greater effect on alternator speed than a smaller pulley does at idle speed. You can believe you're right, but again the OP has shown if someone had followed your advice, he'd be chasing his tail to no avail.
Were this to occur, the exciter would be commanding max field voltage but couldn't produce rated voltage at rated current. So the output voltage of the alternator will actually go down at extremely high speed (well above the design maximum), not up.
The reason why voltage fluctuates a little during speed transients is that the automatic voltage regulator has limited control bandwidth. When you rev the engine and spin up the alternator, the output frequency of the generator increases and the AVR has to compensate for the increasing reactance of the stator by increasing field voltage. The opposite is true during a rapid reduction in speed. Neither of these conpensations can occur instantly, which is why you can see a little bit of a delay and some overshoot.
Last edited by FuzzyLog1c; 09-01-2016 at 11:38 AM.
09-08-2016, 12:53 PM
#26
Man I'm not sure if the battery was on its way out or that 16volts cooked it but I finally got it all together today only to find out the battery is dead and junk. WTF I'm a little upset with mechman too as now my car has been down for 6 weeks. SMH
09-08-2016, 02:14 PM
#28
I like Die Hard Platinum and WalMart Everstart Maxx batteries, depending on my desired budget.
I have had excellent results with PowerMaster HO alternators on both LS and SBC applications. Knock on wood, they have been just as reliable as original GM parts and better than GM remans.
If I only drove occasionally, I might go with an Optima Blue Top to deal with deep cycling.
I think it's entirely possible a smaller pulley could cause overcharging if the regulator is also not functioning/properly. I've been challenged more than once by multiple root causes manifesting as one symptom.
I have had excellent results with PowerMaster HO alternators on both LS and SBC applications. Knock on wood, they have been just as reliable as original GM parts and better than GM remans.
If I only drove occasionally, I might go with an Optima Blue Top to deal with deep cycling.
I think it's entirely possible a smaller pulley could cause overcharging if the regulator is also not functioning/properly. I've been challenged more than once by multiple root causes manifesting as one symptom.
09-08-2016, 11:56 PM
#29
Originally Posted by NIKDSC5
Man I'm not sure if the battery was on its way out or that 16volts cooked it but I finally got it all together today only to find out the battery is dead and junk. WTF I'm a little upset with mechman too as now my car has been down for 6 weeks. SMH
You could try and claim a defect batt, make you feel a little better...
09-09-2016, 06:55 AM
#30
*The excitor is controlled by a pulse that comes directly from the ecm. I'm almost %100 on that.
*The ecm calls for the excitor to work at max load/output during idle/ low rpm because it's designed for the hardware with which it was built (that's my assumption).
So with that theory, it's possible the smaller pulley (making the alternator spin faster at low rpm compared to stock) combined with the stock ecm calling for a full pulse on the excitor is making the alternator over charge. Kind of like when guys try to put a modern alternator in an old car without an ecm and just jump the excitor contact.
That's my theory.
Another one is that your battery had an issue in the first place and the regulator was freaking out?
09-09-2016, 12:39 PM
#31
The fact of the matter here is simple. Swapping pulley sizes WILL NOT CHANGE VOLTAGE. It's that simple. If it did your alternator would produce 16volts either earlier (smaller pulley) or later (larger) in the rpm band. That's it. It would be the same result at different times. I'm not sure why this has become any kind of debate. Only the voltage regulator controls voltage, and it's either working or not.
09-09-2016, 01:58 PM
#34
great. Another freaking week minimum my car is down. SMH
Anyway, I guess I have the excitor circuit misunderstood. Now that we've established my 2 cents has less value than bitcoin, can someone explain exactly how the excitor works then, if it doesn't affect the voltage? I'm usually pretty good with electronic tech, but still novice with motor generator theory.