you Need A Damn Good High Output Alternator

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Grumpy I depend on my van, it's my only means of transportation, and because I'm disabled
I have a good deal of problems if its not running, or won,t start,
I need to sit with the van idling at times for several hours,
and I need the van to start if I need to sleep in the van,
and do that with a few accessories being used with the engine off overnight at times



personally, ID be thinking of a dual battery system with two high capacity, high amp rated batteries.
dependability starts with a good alternator that has the capacity to charge batteries quickly,
under most conditions and without needing to keep the engine rpms much above idle,
with enough capacity to still run all the accessories without any stress,
and battery,(S) that are more than able to handle the amp loads required.
this may require an upgrade over the OEM electrical systems components
many vans used as campers have had similar mods made,
to their electrical and cooling systems

this can,t be a unique request I'm sure its been done dozens of times previously.
youll need a ,set up with a high amp rated switch, relay system,
where you charged both batteries when the engine running and relay switch,
that automatically isolates one back-up battery once the engines turned off,
so you always have the back-up to start the engine.
if you drain the mainly used battery and yes a manual over-ride to that auto relay,
that allows you to use the fully charged reserve battery to start the car,
if the other main battery is drained,
you'll obviously need a good alternator, and some skilled auto electric tech to install,
the wiring and custom wired batteries/relays etc.
example,

heres a 200 amp alt for the 88-91 corvettes
IT COMES WITH INSTALLATION INSTRUCTIONS
I installed on in my 1985 corvette and it made a significant improvement,
in the cooling fan speed and ignition spark strength, smoothing the idle.
Call (800)753-2242
https://www.dbelectrical.com/alternators
800-753-2242
they are knowledgeable and if you ask questions before buying youll have zero problems

http://www.db-starter-alternator.com/c- ... 0-amp.aspx
related links and threads
http://garage.grumpysperformance.com/index.php?threads/battery-or-alternator.10003/#post-43220
http://garage.grumpysperformance.com/index.php?threads/is-my-alt-dead.6964/#post-22890
http://forum.grumpysperformance.com/viewtopic.php?f=36&t=3222&p=8575&hilit=test+alternator#p8575
http://garage.grumpysperformance.com/index.php?threads/how-altenators-work.355/#post-492
http://forum.grumpysperformance.com/viewtopic.php?f=36&t=3222&p=8575&hilit=test+alternator#p8575
 
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if your having alternator/charging issues, I generally find swapping to a 200 amp rated alternator has a rather profound, positive results,
especially if you have an oil/trans fluid cooler with a fan, or other amp draining accessories installed that can tax a stock alternator.
on my 1996 corvette the addition of the higher amp alternator made a very noticeable improvement in the way the car ran.
keep in mind many newer cars use electrical cooling fans not engine driven fans and in traffic that generally results in long time spans at idle speeds where stock alternators are not operating ,super efficiently.

65-impala said:
It's not like it's a on-off switch, but below 2000 alternator rpm, not crank rpm, the output of most alternators drops off substantially. Here is 10SI alternator curves. Below 2000 alternator rpm, a 72A alternator drops to <20A output. That won't run much. The 63A alternator is better at 30A, but still not great.

10si%20perf%20curves_400.jpg



Something to also be careful about is the alternator maximum rpm. I would stick to the 15,000 to 18,000rpm range as the maximum. Using 7.7" crank and 2" alternator pulleys limits the engine to about 4600rpm. Run that engine to 5500-6000rpm once too often and the alternator could explode.
  • 65_Impala Said:
You can make up whatever numbers you want, but pulley ratio is typically closer to 3:1 then 4:1. Alternators typically spin around 2000rpm at 650-750rpm engine idle.

The most important design change on newer model alternators is boosting the idle output. The 140A CS144 will produce 95A or 67% of it's rated output at idle. A 72A 10SI only produces 28% of it's rated output at idle.

a 4:1 alternator pulley ratio will over-rev the alternator at maximum engine rpm on pretty much every GM gasoline vehicle engine that has been produced in the last 60+ years.[/quote]


tjk said:
I used to have big charging problem at idle, Ive got 12-12.5 at idle.
There where lots of different answers but no one could fix the problem. At the end i called a alternator firm and stated my problem and the guy said that most alternators dont charge under 2000-2500rpm
SoIve got me a 7.7" pully on the engine and a 2" on the alternator and BAAM the car never goes under 13.6 even with heavy amps installed.

You said you changed to a smaller pully, what size is that and what size is the crank pully?

My alternator spins at 3500rpm at idle.
7.7" (196mm) / 2" (52mm) x 950rpm idle = 3580rpm

If you let say also has 2" but smaller crank maybe that is the problem, let say you have a 6" and idle at 600-700rpm
Your alternator idle is 1800-2100rpm

This is my thoughts about it.
Maybe it helps ????
 
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