Alternator question

[e vassar]

For a stocker (LS Camaro) running BS3 elec fan,water pump,fuel pump, lights at night. Typical race car...what would be the smallest amp alternator I should run?...thks

[Hacksaw]

Be careful here. A alternator needs to spin about 2500 rpm or more before it starts to break even and produce + current.

[cmracing]

100 amps minimum.

[bigfoot584]

Originally Posted by Hacksaw

Be careful here. A alternator needs to spin about 2500 rpm or more before it starts to break even and produce + current.

Engine rpm's ? or actual alternater rpm's ?


Big difference.

[Hacksaw]

Originally Posted by bigfoot584

Engine rpm's ? or actual alternater rpm's ?


Big difference.

Just checked with an old guy who was a rebuilder and had a test bench. From memory he says about 1800 alt. rpm before they began to produce + current. So on a normal pkg. the ratio of crank to alt. pulley is approx. 3 to 1, which means at idle your not producing current back into the battery. Now with a smaller race crank and larger race alt. pulley to avoid spinning the alt. to the moon it's probably 1100 or 1200 rpm. Also they eat up at least 3 hp, maybe more.