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Hi Amp Alternator & Low RPM

Burt4x4

Burt4x4

1 Ton First Gen
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Hey All ~ I have a high amp 1wire alt. (it may be a 140amp Power Master brand.. still looking for paperwork on that purchase)

First ~ When I first fire up the engine the Alt is still asleep until I RAP RAP Varoom up the RPM = wakes up and is working fine 13.8 to 14 VDC.

Second ~ When engine temp @ operational temp = electric fans turn on and RPM is @ idle my voltage drops to 12.5-8 ish until I move RPM up pass 1100 then I'm looking at approx 13.5VDC

So this damn thing doesn't wake up at startup and doesn't operate sub 1K RPM w/ a load = Booooo :doah:

Does anyone sell a high amp alt that claims to run at lower RPM or Idle?

I idle around 750-850 ish at temp

Thanks
Burt

bbc4.jpg
 
I haven't researched this sense 2005-6 so I am hoping the technology has changed and they have a high output ALT at idle available now...
Pully ratio is another thought...

Thanks
Burt
 
I have a 100 amp power master alt. I start on a closed choke so, never noticed the wake up. I idle below 700 esp with ac on, and run an electric fan, electric drink cooler in cab, have two batteries. My volt meter stays above 13 volts. I have compared my dash meter with 2 different multi meters, so I trust it.
I am running stock pulleys, you should check yours against stock.
 
Yes, I am contacting the pully maker I have to find out if it is a 3-1 ratio.
I also read that the one wire from alt to batt may be making more resistance that it should.. I am using a large ga. wire but gonna swap it w/something new and BIG.

I found an article on Power Master from 2014 and had this to say about 1 wire Alts and power output @ RPM =

"The benefit of running a one-wire alternator is that you only have to install one wire to the battery. The only problem with the exclusion of the field and stator wires is that a one-wire alternator does not turn on automatically when the engine starts. It has no way of sensing the battery’s demand. In order to “excite” (e.g. get the alternator to start charging), the engine must be revved to the RPM where the alternator turns on.

The RPM at which this occurs depends on the alternator/crankshaft pulley ratio. As a rule, alternators must spin faster than the engine. The speed of the alternator is a function of the pulley ratio between the crankshaft and the alternator pulley. This ratio is usually 3:1, which means that the engine’s crank pulley is three times the diameter of the alternator pulley.

Turn-on speeds for Powermaster alternators are at a low 1600 RPM shaft speed. So with a 3:1 ratio pulley, the truck’s engine only needs to be turning at 530 RPM to get the alternator charging. Gone are the days of revving up your engine to turn on the alternator."
 
OK anyone know what the difference is with the two types of cooling fans? What is "better" or the differences ?
I currently have the top style:

Alt_Face.JPG
 
I couldn’t run the top cooling fan with the March alternator bracket I have as it made contact with the bracket.
 
I want to say I'd seen an article that said the upper fan is more efficient.

Don't know when which design started and ended, but I know my 80s car stuff that had higher amp alts stock, used the design in the upper pic.

The CS130 and 144's (and I'm sure subsequent designs) are all said to put out more juice at lower RPMs than the 10/12SI designs. I'd imagine if possible, companies like power master would do what they could to improve on the original output at low RPMS.
 
AC delco made a hi amp alt. I had one in my blazer. It fed a competition level stereo and powered the winch, dual batteries through a Warn isolator.. Don't remember if it was 160A or 185A and it was significantly higher output at idle. Pretty sure is was for emergency vehicles to compensate for all the current to run lights when they're at idle.
 
Thanks all ~ found the receipt it's a PowerMaster 140 from 2002... so damn near 20yrs old :yikes: . I must have had it on my 350... sheezz I got C. R. S. !! :eek2:
I think I'll get something new and put this one in my backup parts box :thumb:

Oh I did find out the air flow of an ALT is thru the back out the front and the top ALT is "baffled" but I could not find anything that said baffled has better cooling. So? ... another life mystery lol
 
I have CS144. Just started it few minutes ago to make sure my memory was working voltage wise. HaHa. Anyhow 14.4 after start. Idle No vrooom vroom. Turn on ac which turns on fan one, drop to 13.4. Fan 2 drop it down more at Idle, but I needs another drink so i gave up. I can get you more voltages if your interested tomorrow.
 
You have an SI series alternator. They don't have tight enough tolerances inside to perform well at low rpm. You would be better off to get a CS series. A CS130 or CS144. I have several stock winding CS130 alternators with the Iceberg case kits. They are only the 105 amp versions but will typically put out 110 amps cold. The one on my big block with stock pullies for an '85, will put out 100 amps at 1100 engine rpm. The old SI alternators couldn't get close to that. It would run A/C, one electric fan and an electric fuel pump at idle and maintain 13.8 volts while at operating temperature.
 
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Yep. My CS130, while I think something is wrong with it now (too many volts IMO) has never struggled with heater, headlights, wipers, and electric fan running. Only see the voltage move when I try and operate the rear window, which typically stalls since its in such bad shape. But still doesn't drop below 12v. At idle.
 
If you have to be careful because a lot of these "high output" alternators only make more power at higher RPM's. As stated above the CS144 style alternators are really good at making decent power at low RPM.
 
Burt4x4 said:
OK anyone know what the difference is with the two types of cooling fans? What is "better" or the differences ?
I currently have the top style:

View attachment 380184
Click to expand...
To answer your questions about the fan, the top one is a SI12, the lower is the older SI10
Those types didn't have the best low idle performance, and that why most people switch to a CS style CS130 or CS144.
And I see you read about the problems of a one wire alternator.
 
Not a fan of the cs130. Remember them having bad rotors. The steel fingers would expand and catch the stator, lock a 350 with serpentine up solid.
Don't know if the cs144 do the same thing.
 
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