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Alternator Shut Off Switch...worth it? Negative Effects?

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Old 12-11-2004, 05:47 PM
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My bearings are absoultely shot in mine. I have to WD-40 it everytime I go for a spin, because it'* always firm. There is a noticable idle difference when it is spinning freely, versus me not lubricating it. Don't worry, I know the alt is opening the door, to make it'* exit, but it still charges the battery, then it'* all good. 5hp is 5hp, no matter where it comes from. As long as it'* a net gain [in other words, it'* not like you gain 5hp, but lose 4 of those horses.. so it includes all the decreasing factors in the "gain"].

If the battery was fully charged, the voltage loss should be minimal. I doubt you could lose that much spark. Although in theory, you will. Less volts coming in, less spark.. but how much may be a better question.


-justin
Old 12-11-2004, 06:02 PM
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Originally Posted by willwren
2240 W = 3.003889 hp
WOOT!!!!!
Old 12-11-2004, 06:27 PM
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not as much as we thought, but its something. Enough to be felt...
Old 12-11-2004, 07:20 PM
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basically the same effect of putting a intake or a muffler
Old 12-11-2004, 07:37 PM
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Is it worth the wear and tear on your battery? Sure, I just dropped in a 1000 CA Red top, but i'm not risking a battery that costs over $100 to do this. If you're trying to run anything else like a stereo, heater, etc. What if you forget to flip the switch?

Could this throw codes as well?
Old 12-11-2004, 09:44 PM
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I think you'd be fine doing this at the track for short runs, but would the reduced spark voltage cancel out the gains? My bet is yes.
Old 12-12-2004, 12:53 AM
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With good coils, wires, and plugs, the 2 volt loss shoudln't make a noticable difference in spark, because it should put out PLENTY of spark on 12v.

Based on my experiences with my friends Lumina, it was more than a 3hp gain. I know that a 190hp Quad 4 "W41" with no accessories on it makes 220-225hp, seeing that all it has for accessories is a ps pump, alt, and ac compressor, thats over 10hp per accessory. My STE has a 18% underdrive pulley that adds 8hp. So theoretically, my accessories take 44hp to run. (alt, ps pump, wp, ac) Divide that by 4 accessories and you come up with 11hp per accessory. Obviously they don't all take the same amount of power to run, but I would bet its probably close.

I will do the test on my STE at the track in the spring, but my tests aren't even going to show as large of a gain as others due to my ud pulley. My alternator is already spinning slower, drawing theoretically 18% less power than it normally would. But, I would bet it would still show a noticable gain in ET'* and/or trap speed. If I can get to a dyno, I might do a test on the dyno as well. Anyways, for <$5 its worth a shot. I've seen people spend a lot more money for a 3hp gain before. (actually I've seen people spend a lot more money to lose more than 3hp before with different exhaust and intake setups and stuff like that)

Shawn
Old 12-12-2004, 10:56 AM
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Originally Posted by dbtk2
With good coils, wires, and plugs, the 2 volt loss shoudln't make a noticable difference in spark, because it should put out PLENTY of spark on 12v.
I'm going to have to disagree. The coil wind ratio in our coils is extreme. A 2-volt loss is nothing to ignore. That'* a major decrease in spark voltage when you look at the big picture. Normally at WOT, most alternators put out 14.4Vdc, so you're talking about 2.5 volts as well.

Remember last year when my alternator was dying? I drove it for 2 months that way until the performance alt got here. I fouled every plug because of low spark voltage. In other words, I wasn't getting a clean consistent burn.

It'* the voltage that makes the spark. It takes volts to jump the gap. If you're going to consider this for the track, at the very least you need to close up your spark gap.
Old 12-12-2004, 10:59 PM
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Originally Posted by willwren
Originally Posted by dbtk2
With good coils, wires, and plugs, the 2 volt loss shoudln't make a noticable difference in spark, because it should put out PLENTY of spark on 12v.
I'm going to have to disagree. The coil wind ratio in our coils is extreme. A 2-volt loss is nothing to ignore. That'* a major decrease in spark voltage when you look at the big picture. Normally at WOT, most alternators put out 14.4Vdc, so you're talking about 2.5 volts as well.

Remember last year when my alternator was dying? I drove it for 2 months that way until the performance alt got here. I fouled every plug because of low spark voltage. In other words, I wasn't getting a clean consistent burn.

It'* the voltage that makes the spark. It takes volts to jump the gap. If you're going to consider this for the track, at the very least you need to close up your spark gap.
Yes, most alternators put out a little over 14 volts (a gm voltage regulator is usually 14.2-14.4v), but a standard car battery is 12.6 volts, not 12. (I'm surprised you didn't know this!) So, actually, it would be a little less than 2 volts that you're losing. Stock coils will put out plenty of spark on 12.6 volts. Yes, it takes volts to jump the gap, but the voltage your coils put out with 12.6 volts is plenty to jump the gap. If your gap is large enough that it can't jump it with 12.6 volts, your gap is too large anyways IMO. After a certain point, more spark isn't gonna help. You can only ignite the air and fuel so well, a bigger spark is not gonna help after a while.

Shawn
Old 12-15-2004, 07:32 PM
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I talk about this mod on www.OQCGP.com and I got a different point of view that nobody here talked about and I changed my mind: I don't like this mod!!

That is an old racer trick, ie: pre computer days. IIRC, a PCM can draw 60 amps to run everything. Ignition, injectors, not to mention the fuel pump. The hot setup is to increase voltage to the fuel pump. Why would you want to run at battery voltage, about 12.5 v, and not 13 to 14 v.
You could save 5 to 7 hp with the alt off. You will loose more when the fuel doesn't push as much, the ignition and injectors are weaker.
Not what you want at WOT. You can get underdrive pulleys for the W/pump and alternator. If you want to lower the drag, disconnect the magnasteer and turn off the radio, heater, and DRL. I recently added a ZZP style alt cable, and engine to body ground cable. Everything works better. Lights are brighter, p/windows are faster, fuel pump is now silent, you can not hear the buzz by the lt/r wheel, and it pulls better because the O2'* don't drop off at the top end. Zoomer uses the OD pulley for his Alt to make sure he has enough power.


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