i have a 4.3l v6 swap with tow rear rads. also have front fan for ac. when the cooling fans are on i shut off the ac because of voltage dropping below 12. with no power draw it is at 13+ on the meter. on top of this when the lights are on voltgage drop more.
this is on a lambo replica. others have gone to 140 amp alternator. my alternator is a cs130 100 amp with a lower mount.
my question is how much difference is there in size with the high output units. i will eventually ask a vendor before buying but want some outside experiences. i will go with a 8 gage line from junction to battery. also, my battery is in front. i see in the diagram that there is a fusible link from the alt to the junction. does this line need upgrading.

thanks.

Been there, done that!!! I have a Koenig Competition replica with rad fans in front of each rear wheel. Vw Fox rads with independant thermostats to turn on/off to temp! (350SBC). You will be amazed about how much BS there is out there.... manufactuer claims etc. For the novice.... someone will state "get a 160 amp alternator"....! Waste of $$$... unless they can supply you a graph showing WHERE (what RPM) 160 amps is accomplished!... normally it will be produced above 2,000 rpm!!! What you require is 100+ amps at 1000 rpm.... cause when you're sitting at a light, both rad fans on, lights, radio, interior fan, AC, misaleneous(sp) other draws, you will be draining the battery! I spent a large amount of time (and money)learning about this. Best suggestion... go visit a GOOD stereo/install shop, they will understand and forward/direct you to a good alternator rebuild shop. (one that can build in low rpm/high amps alternator). Make sure you tell them what you need (amps) and ask for a graph to prove the 'claimed' amperage/rpm. Unfortunately, you may have to upgrade/change up to a larger alt. to produce what amps you may desire... of course this all costs dollars. The other alternative is to find an ambulance alternator.... but they run close to $1000..... in Canada!!!!
best,
Sandy

[This message has been edited by cowans (edited 07-14-2009).]

quote Originally posted by cowans: someone will state "get a 160 amp alternator"....! Waste of $$$... unless they can supply you a graph showing WHERE (what RPM) 160 amps is accomplished!... best, Sandy

I have the 140 amp Powermaster alternator and it was a drop in replacement on my stock GT. It DOES come with a data sheet showing exactly how much power that particular alternator makes at idle. It comes with a smaller pulley so it will run faster at all speeds, so it will take more power to operate, but you won't be wanting for voltage with it.

quote Originally posted by jscott1: I have the 140 amp Powermaster alternator and it was a drop in replacement on my stock GT. It DOES come with a data sheet showing exactly how much power that particular alternator makes at idle. It comes with a smaller pulley so it will run faster at all speeds, so it will take more power to operate, but you won't be wanting for voltage with it.

OK... I'll bite...! How many amps does(your 140 alt) it produce at idle (and I mean engine idle)? As well, my alternator shop told me 'no, don't' when I asked about using a smaller pulley..... something about 'overheating/seising' the Alt. bearings.... as they suggested the alt might be spinning around 10>12K rpm when at max engine rpm...
my 'extra' .02
best,
Sandy

What about running dual alternators? Our Lincoln stretch limos all run 2 alts.

i hope the addtional amps is not dependent only on higher rpms with the smaller pulley. what is your result with the powermaster with the standard pulley. i was warned about increasing the rpms. the alternator will overheat and shorten life.

quote Originally posted by cowans: OK... I'll bite...! How many amps does(your 140 alt) it produce at idle (and I mean engine idle)? As well, my alternator shop told me 'no, don't' when I asked about using a smaller pulley..... something about 'overheating/seising' the Alt. bearings.... as they suggested the alt might be spinning around 10>12K rpm when at max engine rpm... my 'extra' .02 best, Sandy

I don't remember and that data sheet is long since disappeared. I had planned to put on the stock pulley but I couldn't remove it, so I left the small pulley on.

In any case the powermaster is designed for higher RPM so I wouldn't worry about it. The point is that it makes more power than stock if that's what you are after.

This is what Powermaster has to say on their website about pulleys...

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pulley ratios are very important, especially when using high amperage alternators. The pulley that are supplied with the alternator are matched to the winding and power curve. Typically, a street driven car should have a pulley ratio of at least 3:1. If the vehicle has an automatic transmission with a low idle and the vehicle spends a lot of time cruising, then a higher pulley ratio - perhaps 3.5:1 - should be used. Alternators can take high speeds up to 20,000 RPMs for short periods, so overdriving the unit is not a problem.

Powermaster uses a state-of-the-art computer alternator dyno to measure the performance of each alternator we manufacture. Output curves, engine idle speeds, and alternator pulley ratios are carefully considered to assure good drivability at idle and slow cruising speeds.

[This message has been edited by jscott1 (edited 07-15-2009).]