Stupid Alternator & Electric Water Pump Question

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Stupid Alternator & Electric Water Pump Question

Postby djv8ga » Thu Sep 30, 2010 1:48 pm

On my bare bones Vega Hot Rod with a large electric fan and heavy duty-streetable electric water pump, will my I.R.O.C. style (Powermaster) 100 amp alternator get the job done? It's a street car with lights, mild stereo, HEI ignition (no MSD box or anything), and that's about it.

EDIT: I'm thinking of going to an electric pump.
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Re: Stupid Alternator & Electric Water Pump Question

Postby cjbiagi » Thu Sep 30, 2010 3:39 pm

My guess is a 100 amp alternator is fine. My understanding is electric water pumps are not really designed for street cars, why are you running that? 99.9% of our cars run fine with a mechanical water pump and they are pretty much relaible as dirt.
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Re: Stupid Alternator & Electric Water Pump Question

Postby djv8ga » Thu Sep 30, 2010 4:00 pm

cjbiagi wrote:My guess is a 100 amp alternator is fine. My understanding is electric water pumps are not really designed for street cars, why are you running that? 99.9% of our cars run fine with a mechanical water pump and they are pretty much relaible as dirt.

Some electric pumps are made for street use too. They claim the full flow at idle really helps out at idle and in traffic.
Example- http://www.yellowbullet.com/forum/showt ... p?t=232248
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Re: Stupid Alternator & Electric Water Pump Question

Postby T-FATTY » Thu Sep 30, 2010 7:06 pm

Let us know how this works out as i bought a new radiator, electric fans and CSR electric water pump for mine.
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Re: Stupid Alternator & Electric Water Pump Question

Postby spencerforhire » Thu Sep 30, 2010 8:41 pm

The average 100amp alternator should be able to handle the load just fine. A few words of warning; 2 things to avoid are 1-wire units and under-drive pulleys. 1-wire alternators often need to be revved up to start them charging, and under-drive pulleys(either a small one on the crank or a big one on the alt.) almost never charge properly at idle. These concerns are for a street driven car; for race only the 1-wire unit simplifies wiring and the underdrive pulley is a good thing, especially if the RPM's get above 6000-7000.
I'm a big believer in electric water pumps street or strip; they move a lot more water at idle and being able to leave them on after the engine is shut off really shortens cool down time.
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Re: Stupid Alternator & Electric Water Pump Question

Postby djv8ga » Thu Sep 30, 2010 8:43 pm

T-FATTY wrote:Let us know how this works out as i bought a new radiator, electric fans and CSR electric water pump for mine.

I was just giving it some thought. Maybe I should wait to hear from you how well it works.
Will you gain any room to fit the electric fan using the electric water pump?
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Re: Stupid Alternator & Electric Water Pump Question

Postby T-FATTY » Thu Sep 30, 2010 11:39 pm

^^ I won't be working on mine until next summer due to an upcoming move for work. ^^
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Re: Stupid Alternator & Electric Water Pump Question

Postby Sirshredalot » Mon Oct 11, 2010 5:20 pm

Well...just do the math...what rpm does your mechanical pump turn compared to crankshaft speed at cruise?

Odds are that the electric pump will turn at probably about 3000 rpms impellar speed...which is just about right...

You dont really need alot of high rpm flow because we typically dont endure those rpms for an extended period of time.

I would assume that as long as you bought a good quality pump(not a pro-form or cog belt set-up), that you would be just fine...look at the LT1's...their water pumps turn at HALF crankshaft speed and dont over heat.

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Re: Stupid Alternator & Electric Water Pump Question

Postby chevy art » Mon Oct 11, 2010 8:48 pm

shred if you are doing to use all those electronics you may want to get one of the alternators that put out most of the amps at idle and above. in traffic you will be at idle and all the goodies will need juice. art
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Re: Stupid Alternator & Electric Water Pump Question

Postby my79monza » Mon Oct 11, 2010 9:53 pm

My stock V/8 Monza crankshaft pulley is 7 3/4 dia the water pump pulley is 5 3/8 so to me that means the water pump is overdriven in comparison to crankshaft rpm that should increase flow at low rpm.
I would imagine it was done for a purpose.
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Re: Stupid Alternator & Electric Water Pump Question

Postby Sirshredalot » Tue Oct 12, 2010 7:55 am

Yes My79monza...that is done because you have a large engine in a small engine bay, with a small radiator designed for low rpm stop and go traffic...factory redline on that v8 should be about 5000 rpms.

A more ideal flow rate is closer to 1:1...unless you have a low RPM large cubic inch engine.

We are assuming however that for our applications we have aftermarket, more efficient radiators and high quality fans too.

God bless
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Re: Stupid Alternator & Electric Water Pump Question

Postby starfire383 » Thu Oct 14, 2010 9:30 am

If the powermaster is an original style alternator, no it won't keep up at low speeds. Wouldn't matter if it was a 120 amp, the idle output just isn't there. When GM went to electric cooling fans they went to the CS style alternator for a reason. Let the voltage drop and the amps will skyrocket & prematurely burn up expensive fans & pumps, even if voltage never drops enough to cause a no-start. Ohms law is a bitch, but CS144s are as close to bolt-in as you'll get, and can be sourced cheaply with a bit of ingenuity.

good luck
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