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100 amp alternator mod

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  • #16
    hey i like to read on here. since i don't have the money to make mine as fast as yours. and i like the look of my Z.

    so anyway. with the mod.

    i want to go to bed. i drove over 100 miles round trip after work to take a look at an 85 turbo. with 82000 miles on it.

    your arguements are all valid. but if you are worried about loosing a few horsepower on your alternator, take it off. now lets be realistic here. i have a large stereo. i can't see great at night, and like very bright headlights, and i also like to run my heater and rear defroster at night with everything else on. with my chevy alternator i can now do that at a stop light (one of two in wyoming :roll: ) and still put out 14 volts at idle.

    heres a few pictures. i do feel more power in the higher rpms like or-zman stated.

    i'll talk about it more tomarrow. i have to get up at 5.00 to get to work on time tomarrow.









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    • #17
      instead of the tiny stock wiring, i removed the nissan alternator harness and used 0 gauge welding cable for my battery cable. thats all there is to hook up. one wire hook up. try that with any junkyard alternator.

      when i sell the car for a turbo, i can take out my alternator and bracket and hook up the stocker and return the wiring harness to the proper location. it'll take 10 minutes. since i removed all the emissions crap and made block off plates.

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      • #18
        84z31 wrote: your arguements are all valid. but if you are worried about loosing a few horsepower on your alternator, take it off. now lets be realistic here. i have a large stereo. i can't see great at night, and like very bright headlights, and i also like to run my heater and rear defroster at night with everything else on. with my chevy alternator i can now do that at a stop light (one of two in wyoming :roll: ) and still put out 14 volts at idle.
        It's an interesting idea at the very least. What size is the ribbed pulley you would use for turbo or 87+ cars? I don't think anyone was critical of the idea or worried about losing a few horsepower at most (at least not that I read).

        Um... the voltage in the Z31 electrical system should still be regulated to 13.5 if memory serves, not 14 (at least not according to my guage on either stock or maxima alternators) if that alternator is internally regulated higher than the stock alternator, then that would explain the additional voltage in the system along with the additional amperage. Not sure if this would be beneficial, maybe it could help fuel pump performance?

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        • #19
          ^Alex...point well taken...I think. :? Now that I really think about it, I'm not sure that a 100amp v.s 70amp alternator would really make a heck of a lot of difference on engine load...under or over driven. I very well could be bass ackwards on my thought process. Wouldn't be the first time. :wink:

          As for the benefits of having more amps in your electrical system...the proof is in the pudding. More usable amps below peak output means increased efficiency for anything that uses that power.

          We can only really control one of the variables reliably and with any consistency...that is amps. Since voltage and resistance stay the same (relatively) then the more usable current (amps) you provide your electrical components the better. (within reason of course) E over I / R and P=IxE and all that good stuff...

          It really doesn't matter if you have huge current demands from a superwhamodyne stereo system or wtf ever else you install. Electrical systems perform better when provided with consistent and reliable power. Stereo, fans, ignition, lights, whatever.
          Just stand back and throw money.
          Performance costs money.
          Reliable performance costs more.

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          • #20
            since I have the quest fusible links I used the quest alt harness uncut.... it's the same configuration as the z31 alt, just thicker

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            • #21
              in the service manual it says on page EL-22 that the alternator should put out with the regulator 14-15V.

              it even gives the rated power out put in amps through the rpm ranges.

              to get the full 70 apm rating of the alternator the engine has to be spinning over 5 grand. just for your info.

              i would like to find a chart for the chevy alternator.

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              • #22
                84z31 wrote: in the service manual it says on page EL-22 that the alternator should put out with the regulator 14-15V.

                it even gives the rated power out put in amps through the rpm ranges.

                to get the full 70 apm rating of the alternator the engine has to be spinning over 5 grand. just for your info.

                i would like to find a chart for the chevy alternator.

                Interesting, you're right, regulated from 14.1 to 14.7 volts for turbo alternators. My guage must have always been incorrect then.

                That's alternator RPM
                by the way, and part of the standard output graph. Every good remanufactured alternator should come with a graph in the box from testing (at least bosch units do). You would need to figure the drive difference to get engine RPM number for peak output. The neat thing you could then do is step down in alternator pulley size until you are further "up" on the curve to get your desired amperage (or close) at idle.

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                • #23
                  i wish i could find one. but i only had a few minutes to search the internet this morning.

                  i'll look somemore tonight.

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                  • #24
                    Ok, I don't get it. You claim that you can feel a difference in engine performance. Put on the brakes for a minute! Lenz's law states that the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it. And there is always a percentage of lost energy when converting mechanical energy to electrcal energy. The more current you flow to power your ignition, the more drag you will create on the armature, and waste with converting the energy. Also that means running extra electronics will slow you down (and effect your gas mileage, the energy has to come from somewhere).

                    Also you are overdriving that one which will suck more power from your engine. I really don't see how this thing is making you faster. It should noticably slow you down.
                    KILL HADJI

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                    • #25
                      perhaps the better spark eliminates some loss of combustion efficiency which would mean less explosion energy is lost and more becomes mechanical to turn the schwarzenegger

                      it might offset itself, only testing would tell you accurately, but I bet it would be within the margarine of error

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                      • #26
                        I will look into making a bracket to mount the quest alt in the stock location, then at least it's easier

                        of course the wires and fusible links then become the weak point, but then wiring is much easier and not everyone can fab brackets

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                        • #27
                          but also remember that your not always going to be pulling 100 amps. so there is not always that much load on the engine. so if the alternator is able to put out more amps at lower rpms it would make it more efficient then a lower powered unit.

                          my alternator was dying. i didn't want to pay over $100 to replace it. i saw value in more bang for the buck. so i bought the chevy and fitted it in.

                          i run electric fans, and over 600 watts in the sterio. the stock alternator wouldn't work well with the fans and kept draining the battery. even while idling. now my battery stays up at 14 volts all the time. and the cable to the battery is much better at delivering power to the battery. making it even more effiecient. i think the stock set up is like 10 gauge.

                          things to think about

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                          • #28
                            the alternator in my cousn's a4 says right on it 70-140A output...so down low it's 70, up high it's 140.... however the audi alternator isn't that wide, so the range might be larger than the nissan/hitachi alts....

                            my guess is the quest alternator is similar, ie 120A fusible link would indicate that is the max with an idle amperage ~40A less

                            however if you have only 70A maximum from your alternator then obviously you wouldn't have much at idle, 30-40 maybe?

                            as you may know the audi's are highly motorized and theres electronics for everything including butt warmers, the fuse area is half of the panel below the steering column...

                            the bigger alternator just gives you more overhead and freedom to do things without draining the battery, the alternator should provide sufficient power to run the car without a battery hooked up

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