big alt=less HP??

[ngsm13 5,000+ posts]

hey cybe... blow me fuker

You're an idiot, plain and simple.

NG

 

[jsloan10 10+ year member]

A high output alternator will put a noticible strain on the engine when the electrical system is demanding alot of current.

My 90 Cav. had a 160 amp alt in it and you could feel the the engine bog slightly on the freeway when the big bass notes would hit, this was with a 1200watt rms amp(3.1L v6).

A larger pulley will reduce the strain on the motor but you will trade off availble amperage at idle and possibly suffer voltage problems at stop lights.

A long time ago when I was in school they did an experiment where they replaced the wheel of an exercise bike with a stock chevy alternator to teach us about electricity, we would hop on the bike and pedal for all we were worth in order to light up a series of automitive bulbs and I can say from physical experience that alternators do indeed require alot of kiinetic energy in order to create power.

In short, alternators do consume a noticable amount of engine power, this is why hard core dragracers remove them entirely from their cars.

 

[saywhat? 5,000+ posts]

so is it not smart to run a couple HO's on such a small motor (beetle)....maybe just one?

 

[jsloan10 10+ year member]

I would go with just one if I were you and use an alt rated for no more than 140amps peak output then add a second battery.

For dual batts there are 2 ways of doing it-

You can do it like they do in deisel trucks and run two identical batterys in parrallel, this way you will have alot more available current for the system.

In this setup the batterys need to be Identical to avoid having the batterys pull current off of each other, this shortens the life of the batterys considerably so two Identical batterys (age/type/brandname) are recommended for maximum reliabilty.

If you want to use a two different batterys you need to use an isolator. Your regular battery will run the factory electrical system and the second battery will run your amps. The Isolator works by allowing both batterys to charge off the same alternator but stops the batterys from drawing current from each other.

 

[maylar 10+ year member]

you're incorrect, that power has to come from somewhereand whoever said alts are 75% efficient is also quite incorrect, try less than 25%

Typically 50-60%. Not bad, really. Specialty units can be over 70%:

http://www.wranglernw.com/ecotech/specs.asp

Yes, the power comes from the engine. A high output alt might have a bit more drag because of larger rotating mass but the alternator alone would probably not be noticed. The real power drain comes when you put load on it. Like someone said, 1 hp = 746 watts.

Since an old VW Beetle was only 35 hp or so to begin with, adding a couple hp load with a big system is prolly a bad idea.

 

[audiolife 5,000+ posts]

unless you trick out the engine to do more power. dual carbs and such.

 

[Acidburn 5,000+ posts]

Typically 50-60%. Not bad, really. Specialty units can be over 70%:
http://www.wranglernw.com/ecotech/specs.asp

Yes, the power comes from the engine. A high output alt might have a bit more drag because of larger rotating mass but the alternator alone would probably not be noticed. The real power drain comes when you put load on it. Like someone said, 1 hp = 746 watts.

Since an old VW Beetle was only 35 hp or so to begin with, adding a couple hp load with a big system is prolly a bad idea.

my mistake, i stand corrected

 

[saywhat? 5,000+ posts]

unless you trick out the engine to do more power. dual carbs and such.

im deffinately runnin performance parts to make up for weight and such.

 

[andy1234 10+ year member]

i have a freind that keeps on telling my my car is trying to over heat bcuz of the alternator is this true? im chanign the therma stat today, no leaks or anything,clean fluid, and i put a new air filter in last night

 

[jsloan10 10+ year member]

An alternator has nothing to do with your engine overheating, the workload on the engine/ quality of oil and health of the cooling system does.

 

[audiolife 5,000+ posts]

the old soundstream spl van had like5 alts in a form of a star pattern on it. under load during a burp the belt would squeak and sometimes break lol -not kidding.