Club Cobra - Alternator help

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Alternator help

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07-06-2015 04:00 PM - permalink

BOBOCobra

Guys, I have two high amp puller fans, plus all the normal electrical items and I am struggling with idle amperage. Current amp is 105 and I idle at about 700 rpm (I like is low and lumpy). When both fans running volt meter drops to 12 at idle. At 2000 rpm plus I have no problems, steady at 14 volts. Both fans when running pull about 50 amps. Crank is 5.25" and alt pulley is 2.25" so I could overdrive it a little more with a slightly smaller pulley but I am not sure about that. I can pull the second fan wire direct to the battery post and that makes the volt meter look better but that does not solve the amp deficit. Ideas? bigger alternator suggestions? It has not been a big issue but on a hot day in a traffic issue in LA I could get into trouble with battery drain. thanks, Dave

07-11-2015 04:54 AM - permalink

BAsque1

BOBOCobra:
I had the same problem and opted for a 200 amp alternator, albeit, criticized by many, it worked, I also increased the size of the pulley because when the fans cranked on the belt was screeching a bit and saw a drop in amperage. Since I did this my problem is solved. Got the alternator from Tuff Stuff in chrome and 1 wire call them up and state your problem and type of engine. I paid $400 or so for my alternator.
Lou

07-11-2015 09:06 AM - permalink

Xack

Bobo,
I would seriously look at your cooling. It should not take such huge fans to cool your engine. I'm not sure what HP your running or the configuration of your engine, but per normal conditions you should not have to push a great deal of air through your radiator. Efficiency is very important here. Shrouding is very important to get the air through the radiator with less power. The cooling system modified by Vern poses some problems and can be fixed with some help. I'm testing an Edelbrock Water Pump with a smaller pulley attached to it (it's designed for racing and flow at high RPM. Idle is not it's hallmark). I'll definitely keep you posted on it's performance. Also, Davies Craig sells EWP which is an electric in-line water pump. This draws less amps than your fans. Don't get me wrong, you need a good fan, but you may be putting your money and effort into the wrong place especially if it's draining your battery when you sit at the stop light.

07-11-2015 10:19 AM - permalink

BOBOCobra

thanks for the responses. I tore out Verne's set up and did it right. Its all shrouded, plumbed properly... The cooling issue is in the summer when its over 100 ambient. the car runs consistently at 100 degrees over ambient and the issue is only in heavy traffic on really hot days. As an example I gutted the t-stat to run a test and it was 45 degrees out, moist air, and it ran at 145-150. With the 180 t-stat it runs at 185 if I'm moving in any weather. The cooling set up is efficient. Fan #2 kicks on at 195-200 degrees and kicks off as soon as I start moving. But...fan 2 is a big mover and it will kick the temp down but for that time it pulls a lot of amps. It is just an idle thing. I want to put on EFI this winter and looking for a little more power to run the controller.

07-11-2015 10:21 AM - permalink

BOBOCobra

Lou, Did that unit fit without modification of the mounting brackets? I have a "small" case with very little room and that looks like a large case. I like the 200 amp option if I can get 60-70 at idle.

07-12-2015 11:54 AM - permalink

Xack

OK I should never assume. Sorry about stating the obvious.

07-12-2015 12:01 PM - permalink

BOBOCobra

Its all good, you are right on that the "factory" cooling is not correct. that would need to be job 1. I found a guy that will rewind my alternator to about 160 amps and its all in at 1500 rpm. So, at idle I should be 60 amps, which would be fine. I will pull it and get this done in a week or so.

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