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100 amp alternator mod

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  • 100 amp alternator mod

    I recently installed this on my NA and I couldn't be happier. Ross (84Z31 who is a silent member here) came up with the idea and I jumped on it right away.

    My installation thoughts are in that post and he has links to his other posts on that link that have the initial pics and info. All the info you should want is there but if you have any questions at all don't hesitate to ask. I will do my best to answer and make sure that Ross is consulted in the process as needed.

    Here is a link to the alternator we are using:
    http://store.summitracing.com/egnsearch ... &x=24&y=14

    I don't have anything to gain in this venture. I just saw the benefits of his idea right away and jumped in with both feet as I usually do when I see or hear about something that sounds like a great idea. Also, Ross is a great guy and I would like to hep him get some exposure on what I feel is a great idea.

    There is one open question on this mod....will the alternator and bracket actually fit on the turbo (opposite side). My money says it will and there is one turbo owner who has agreed to test it. Anyone who would be willing to test this on their car would be much appreciated. Or to help prove a "proof of concept" that his bracket will work on both NA and turbo. PM either of us if you would be willing to help with this proof of concept.
    Just stand back and throw money.
    Performance costs money.
    Reliable performance costs more.

  • #2
    I'm not sure how much of a benefit this is as it would actually degrade engine performance slightly. The alternator's amperage rating really has less to do with the voltage output curve of the given alternator anyway, and even though those are 100amp at peak, they might not even perform as well as the maxima alternator at idle unless you overdrive them with a smaller pulley.

    My maxima 90 amp alternator keeps up just great even being underdriven by a UR pulley, with a aftermarket stereo and subwoofers cranked up to the max, headlights and every other accessory on and I've still got 13.5 volts at idle.

    I would like to see some pictures and information posted by Ross if he wants people to buy them (and someone to test it for him).

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    • #3
      wow that sure beats my $25 120A quest alternator

      Comment


      • #4
        G-E wrote: wow that sure beats my $25 120A quest alternator
        This is the part where I say

        *OUCH!, BURRRNNNED!*

        And then ask you to post your quest alternator install instructions.

        Comment


        • #5
          I mentioned to that guy once about the negative effects of that alternator install possibly resulting in some performance loss but he didn't take to that very well at all and got real defensive about it!
          http://youtube.com/c/zcartube

          Comment


          • #6
            300zxt wrote: I mentioned to that guy once about the negative effects of that alternator install possibly resulting in some performance loss but he didn't take to that very well at all and got real defensive about it!
            Well, his defence would probably be that it's going to depend on the load on the system, as the alternator puts out as much as it needs to given the driving force it has to work with.

            I would say that regardless of load, a heavier armature equates to more rotating mass to begin with, which means more inertia and slower acceleration/deceleration. Tiny, little, itty-bitty amount probably...

            Comment


            • #7
              [quote]Jason84NA2T wrote:
              Originally posted by G-E
              wow that sure beats my $25 120A quest alternator
              This is the part where I say

              *OUCH!, BURRRNNNED!*

              And then ask you to post your quest alternator install instructions.
              and then I say "damn you and your writeups, I didn't have a good camera at the time"

              seriously I'd have to tear it apart to show all the mods, if you have basic fabbing skills and access to a welder it can be done dirt cheap, and I got my alternator from the wrecker for $25 with 6month warranty not bad eh?

              the only problem with my setup is that I chose to make the adapter plate move it forward so the belt uses the a/c belt section of the crank, and therefore I had to make an idler pulley from the a/c idler (used a quest idler since it was 10yrs newer) for the waterpump belt... but it could be done with a z31 idler I'm pretty sure..... the idler could interfere with intercooler piping however, and the idler bracket is mounted just next to where the driver's motor mount attaches to the block on a turbo

              I will take better pics of the whole setup now that I have a good camera around and the driver's exhaust is off

              Comment


              • #8
                Jason84NA2T wrote: Well, his defence would probably be that it's going to depend on the load on the system, as the alternator puts out as much as it needs to given the driving force it has to work with.
                the load does matter, my k-car's alternator belt is tensioned just "right" but it wants to squeal whenever I've used the cd player without the car running, or maybe headlights & blower motor driving around in the city, or even just re-starting it a bunch of times.... it spins though even when it's squealing, but you can feel it slowly resisting less and less until it stops, I found out my blower motor uses the most juice of any accessory I have....

                thing is any tighter and it really drags on the engine, any looser and it won't spin the alt.... the alternator resists being spun when the juice is low, and the alternator is by no means big, in diameter it's like 3/4 the z31 unit and also 70a (denso is the good one)

                Jason84NA2T wrote:
                I would say that regardless of load, a heavier armature equates to more rotating mass to begin with, which means more inertia and slower acceleration/deceleration. Tiny, little, itty-bitty amount probably...
                as I'm implying above, the rotating inertia is not a factor in this, you're spinning something that's about as heavy as the water pump pulley inside a fixed casing, the resisting force of the emf is the load, sure a larger alternator will have a larger field and coils further from center giving it more leverage to slow the shaft down.... but basically any significant load from the alternator is not mechanical unless the bearings are toast

                Comment


                • #9
                  All I can say without quantified proof is that...my experience was that this alternator is giving me more consistent voltage, the "drag" on the engine should be minimal compared to any other alternator. (lets just say 1-2 hp for conversation sake) And... everything electrical really likes the available power. Windows, fans, stereo, lights, whatever.

                  Yes, a bone-yard alternator will be cheaper...no argument here. But if you are on the verge of needing a new alternator and want a reliable unit for the long term...??? Personally I would spend the $70+ shipping and either buy or fab the bracket before buying a used alternator that may last a few months and still require modification work.

                  Just throwing this out there as an option.
                  Just stand back and throw money.
                  Performance costs money.
                  Reliable performance costs more.

                  Comment


                  • #10
                    mine is still bigger than yours.... just throwing that out there too

                    you only have to make brackets or whatnot once.... just replace it with the same thing if it dies.... and at $25 I'd buy two at a time and still save

                    I keep a spare alternator (with belt) and coil in my k-car trunk.... along with spare plugs and silicon grease for emergencies hehe

                    and a dewalt drill case full of sockets and wrenches for roadside fun....

                    Comment


                    • #11
                      btw just so you know, the quest alternator is designed to sit on the driver's side of our engine, assuming you used the quest's bracket I think it would stick out a touch going by what the crank pulley looked like.... however using the 84-86na bracket might line it up almost perfectly and you would only need a spacer for the adjuster bracket most likely

                      I have an 87 so it's on the passenger side like all turbos, also note the quest alt pulley is 5 rib not 4, so you need to line it up as best you can with either edge and use those 4 ribs only

                      in short this might actually be a really easy upgrade for early non-turbo cars

                      Comment


                      • #12
                        [quote]G-E wrote:
                        Originally posted by Jason84NA2T
                        Well, his defence would probably be that it's going to depend on the load on the system, as the alternator puts out as much as it needs to given the driving force it has to work with.
                        the load does matter, my k-car's alternator belt is tensioned just "right" but it wants to squeal whenever I've used the cd player without the car running, or maybe headlights & blower motor driving around in the city, or even just re-starting it a bunch of times.... it spins though even when it's squealing, but you can feel it slowly resisting less and less until it stops, I found out my blower motor uses the most juice of any accessory I have....

                        thing is any tighter and it really drags on the engine, any looser and it won't spin the alt.... the alternator resists being spun when the juice is low, and the alternator is by no means big, in diameter it's like 3/4 the z31 unit and also 70a (denso is the good one)

                        Jason84NA2T wrote:
                        Originally posted by Jason84NA2T
                        I would say that regardless of load, a heavier armature equates to more rotating mass to begin with, which means more inertia and slower acceleration/deceleration. Tiny, little, itty-bitty amount probably...
                        as I'm implying above, the rotating inertia is not a factor in this, you're spinning something that's about as heavy as the water pump pulley inside a fixed casing, the resisting force of the emf is the load, sure a larger alternator will have a larger field and coils further from center giving it more leverage to slow the shaft down.... but basically any significant load from the alternator is not mechanical unless the bearings are toast
                        Any way you look at it, what you said just completely re-enforced the exact points I was making.

                        The rotating mass of the armature is a (tiny) factor though, have you ever pulled one out and weighed it? easily 5 lbs.

                        Comment


                        • #13
                          Jason84NA2T wrote: Well, his defence would probably be that it's going to depend on the load on the system, as the alternator puts out as much as it needs to given the driving force it has to work with.

                          I would say that regardless of load, a heavier armature equates to more rotating mass to begin with, which means more inertia and slower acceleration/deceleration. Tiny, little, itty-bitty amount probably...
                          Yes, the pulley on this alternator is smaller than stock. I actually measured it but cant find the notes now. After measuring (outside of the pulleys but the 100 amp installed) Stock pulley is near or right at 3" the 100amp pulley is 2-2 1/4 inches. So yes it is naturally under-driven.

                          If anything I noticed better acceleration and upper end revs. This could very well be because my old alternator was on its last legs and wasn't supplying the needed power to the ignition. Who knows. Like I said before, I can attest to improved electrical performance over the beat up 200k alternator I had before, but how can you quantify the results + or -. :?:
                          Just stand back and throw money.
                          Performance costs money.
                          Reliable performance costs more.

                          Comment


                          • #14



                            the idler for the waterpump now that the alternator uses a/c belt position




                            you can see the 3/8" offset plate between the alternator bracket and block, you can also see that I drilled out the bracket to use a through bolt with a nyloc nut instead



                            the total package

                            Comment


                            • #15
                              [quote]OR-Zman wrote:
                              Originally posted by Jason84NA2T
                              Well, his defence would probably be that it's going to depend on the load on the system, as the alternator puts out as much as it needs to given the driving force it has to work with.

                              I would say that regardless of load, a heavier armature equates to more rotating mass to begin with, which means more inertia and slower acceleration/deceleration. Tiny, little, itty-bitty amount probably...
                              Yes, the pulley on this alternator is smaller than stock. I actually measured it but cant find the notes now. After measuring (outside of the pulleys but the 100 amp installed) Stock pulley is near or right at 3" the 100amp pulley is 2-2 1/4 inches. So yes it is naturally under-driven.
                              A smaller pulley on the accessory would make it overdriven not underdriven. But i really don't see how you will need 100A unless you install some many serious electronics.
                              KILL HADJI

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