Alternator HP Loss

[Robert Davis]

I recently had to add weight to my car for a N/A class I am participating. I added an extra battery in the trunk and a Painless Dual Battery Controller. One option on the control switch allows both batteries on line all the time, not just for starting and charging. Since I now have 2 Optima batteries how much HP would I free up if I installed another cut-off switch and took the alternator off line during the run. I have a 100 amp alternator. I have a Magna Fuel ProStar pump, electric fan, water pump and a MSD Digital 7 ignition. I would think the two batteries would support the draw for the pass.
Thanks, Robert

[Six_Shooter]

With the way alternators have been made the last few years with improved bearings, better balancing, and lighter components mechanically less then a 1hp, maybe just over at higher RPM, add in the electrical parasitic HP loss of about another 3 or 4 HP at most, the difference is negligible, especially when you consider the offset of any gain by not having the mechanical drag, by the lower power input to the ignition system, and other controls, you probably won't see any gain or not enough to warrant disconecting the alternator during a run.

I don't think I'm doing the math right, but if it is, to create 100 Amps of current it would only take 1.9 HP, at 100% efficiancy, factor in that most electrical components are between 70 and 50 % efficiant, at worst that would mean 3.8 HP to possibly gain from electrical parasitic HP loss.

I'm sure both Sparky and esspecially RRRRRRRAAAAAYYYYY (I can never remember how many letters are used :lol: ) will have some input on this.

[RRRAAAYYY2]

Here is my crack at the answer:
http://www.svapowerproducts.com/html/how_much_hp_does_an_alternator.html
If it is a 12volt system the alternator will produce more power through a hotter spark then you will ever lose using it.