I have heard of people doing this, but I am not sure on how to do it. I just wanna be able to shut off when racing and then turn it back on when done. Anyone know how to do this. I assume it has something to do with the plug with the red and black wires that plugs into the alternator seperate from the positive wire?

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Founder of the Greater Cincinnati F-Body Association
Greater Cincinnati F-Body Association
1988 Yellow Trans Am GTA
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I don't think there will be any real benefit to doing this, but I'll take a shot at it. Since the alternator is grounded to something(I think it is) just wire the ground into a toggle switch(2 terminal)and another wire to ground. Then when the alternator is grounded the alternator will stay on, and when it's not it will be off. maybe it's not grounded. I'm for sure on this, somebody else should chime in. But this is the basic idea. I think though that it's not the alternator itself that robs horses(very few though), but the belt that drives the alternator. Plus if your battery isn't in tip top shape then you could actually do worse in the race without the alternator, miss at high RPMs, you get the picture. my advise is that you leave it on there.

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'86 IROC 5-speed
305 LG4
edelbrock performer rpm intake
edelbrock 600 cfm carb
msd pro billet hei distributer
'95 3.23 rearend
hotchkis rear suspension
PST front polygraphite suspension
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I'm gonna have to second what iroc5speed said: it's not a good idea to race without an alternator. The belt turning the alternator is what robs power, and the alternator will be turning whether or not the alt is charging. Plus without the alternator you have less voltage supplied to the car which could adversely affect your ignition system.

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91 Z28
Come see The Vicious...

 

i know this because someone near me does this. you cannot shut off the ground because it grounds through the case also. the alternator freespins and has no drag when you turn it off so it does help.

best way is to run external regulator and just put the switch on ignition power to the regulator. i think with internal regulator you would have to run two switches or it could selfexcite.
i have heard fuel injected cars do not like low voltage because the fuel pressure drops.

 

Let's try to straighten all this out. In order to isolate the alternator with a switch, you'll have to put the switch in series with the wire that goes to the battery from the alternator (the large one by itself on the alternator). That means running a large-guage wire into the passenger compartment from the alternator to the switch, and another back out from the switch to the battery.

As to whether it will take a load off the engine, yes it will. But, with our computer controls, the net effect will be negative, since the computer stuff likes all of its voltage.

Bottom line - don't bother doing it. It ain't worth it (I did it on my non-CC V6 Vega back in the early '80's, didn't make a lick of difference in my times).

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Oh, you've gone non-CC.

Still, it ain't worth it.

 

Hmm... I don't think that I would attempting shuting off my alternator... like eveyone else said.. the belt would still be turning..which would mean you would have accomplished nothing...If you want to why not just take the whole thing off and just get the battery re-charged for every race, i think that would get pretty annoying though

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~1985 Camaro Z28~

V8,305,700R4,K&N Edlebrock Air Filter,& MSD 8.5MM Super conductor Wires,

 

If you shut the alternator off the alternator is still rotating- so the only savings in Horespower would be from the drag induced by the alternator (current wise).
If you do the math conversions:
A 140 amp alternator at 14 volts puts out 2.63hp or 1960 Watts; or pulls out 2.63hp from the engine.
Is that worth a misfire at high end rpms?

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86 Iroc, 355 ci, Dart II heads, holley 750, Victor Jr., Hooker super comp headers, 4.10 rearend, MSD 6A, roller valve train, high stall converter, true dual flowmaster exhaust, NOS- 150 shot.

 

I've seen back to back runs that show less performance when the alternator isn't charging. Your spark output is a function of the input voltage/amps. With the alternator working you end up with better spark. Your ignition system is desiged to work with an alternator at around 14 volts.


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82camaro

 

Removing an alternator completely from a race car gives you about 3hp at the most.

Using a switch to disconnect the power won't have any effect at all on power. The belt still turns the alternator.

To stop the alternator from charging you need to disconnect the field wire. If you look at the smaller wires on the alternator, field is marked with a F. Older 10si alternators (1 big red wire and a 2 wire plug), the field wire is the small brown wire in the 2 wire plug. The newer style alternators have a multi small wire plug, usually 4 wires. You have to look at the plug for the F to figure out which one is the fiels wire.

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87 IROC-Z SuperPro ET Bracket Race Car
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