How about an alternator that you can manually set to charge the battery or not? That should free up some horses, right? Hey if you're taking the car to the track you probably dont need an alternator if everything is wired to the battery!

 

The belt is still going to be spinning the alternator pully, so I dont think turning it off will make any difference.

 

Ive seen that done before with a toggle/relay circuit.

By reducing/eliminating the load on the alternator you can free up some power. While the alternator off the vehicle is easy to spin, once the motor is generating current it takes power to rotate the alternator.

James

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1985 Z-28, 350 TPI, T-Tops, edelbrock 6085 heads, ZZ4 cam, accel base/runners & 24 lb/hr inj., ported plenum, everything gasket matched, crane AFPR, SLP 1 5/8 headers, single 3" flowmaster catback, 3" Catco cat, modified tranny, 165 ECM & ARAP code, MSD 6AL/wires, edelbrock STB, Spohn SFC, GW "wonderbar"

 

chevy high performance did a test on this once.. the very small power gains in hp dont make up for the small power lost in the electrical system.. its an urban legend, doesnt work(according to more than a few mags and racers)

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83 Z28--not a pretty site, sold thank goodness

74 Z28-- 383/400, green on black. pretty clean. FOR SALE!!!

 

I heard the same thing. The drop from 14.4v to 12 or so reduces the efficiency of the ignition system, fuel pump and also alters the response time of the injectors (If you run them) plus the eletrical demands of the fans could drop the voltage even more.

If you're saying I don't have fuel injection or electric fans, maybe ditching the stock fan and getting an electrical fan would amount to more gains than disabling the alternator.

 

well if you had a deep cycle 14.4v battery...

 

...unhooking the alternator would still only give you about 3 hp.

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82 Camaro:
350
Erson cam, ported heads,Comp Cams 1.6:1 rocker arms
Edelbrock Performer RPM intake, Holley 600
Crane Hi-6 ignition, Accel supercoil
TH350 tranny with 2500 stall.
Eibach Pro Kit
SLP 1 3/4" headers

 

I can't help but put in my 2¢ -

First, it would be very easy to do, or at least should be. Simply put in an on/off toggle switch to turn it on and off. The wire you would switch is the "F" terminal. On my '91 Camaro, there are two wires going to the side/rear connector - a larger red wire that is the sense wire connected to the battery and a smaller brown wire that has +12 with the ignition "on" via the fan fuse. The smaller brown wire is what you want to turn on and off.

With the alternator spinning and zero volts on this wire (switch "off"), you will eliminate any load the alternator would present to the engine. The amount of load the alternator presents to the engine just spinning (not operating) is very negligible.

I don't know how much load the alternator will give to the engine when normally operating - I would think more than 3 amperes, but less than 10. I think two fans (about 30 amperes two) will present a significant load but don't know exactly how much. I would be curious to know.

But as was correctly pointed out above, and more importantly, you'd loose several volts (from ~14.0 to ~12.5), something very important for the ignition (unless you have a magneto). I think you would lose a lot more than you'd gain just by the voltage loss.

Jacobs make DC-to-Dc converter (called the ACCUVOLT for ~$300) that will maintain a regulated 14 (or 16 depending upon the model) volt output as long as the input is between 9.5-14 volts. It maximum continuous output is 50 amperes, 70 intermittant. This would negate the loss of voltage that turning off the alternator would cause. This is how I'd solve the voltage drop problem - it looks like a nice power supply.

Another possibility would be to use a 16 volt battery, such as a three post style that Summit sells (p/n 903-16V324 $180) that would give you enough voltage, but you have to use a 16 volt charger or design a circuit to use the alternator to charge it (there are several ways that you could accomplish this).

Nevertheless, if you want to try and see if there are any benefits, simply remove the fan fuse (this also provides current to operate the fan relays). This will turn off the alternator.

 

Just curious, but would the Alt be running full (regulator not switching) and would this have detrimental effects on the Alt?

Or does the Alt not switch the regulator on without being excited by some amount of voltage?

 

Also the extra weight from the deep cycle battery would not help any at all.

 

8Mike,

Your second guess is correct. Without power (+12) to the "turn on" pin, the alternator (voltage regulator) will be off and not produce any current. It would only be "free spinngin" as they say.

 

If it's that simple, why isn't everyone doing it? As far as the track goes, the losses outweigh the gains. You'll have a less efficient spark and the gain of a few hp just isn't worth it. You'd eat batteries like crazy with the switch. With the draw on the battery and nothing to charge it, it wouldn't take long to kill the charge.