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On 12 Nov 2002, at 10:09, Wilson wrote: > Your last message brings us to the question of amps. If you re-wind your > generator how much more juice does that give you? Also, some people have > discussed switching theirs with a Type 4 Alternator, what power rating does that > have? And after any of these things are done, isn't the gauge of the stock > wiring going to be too small to handle such increases? How do you go about > rewiring or refusing your Type 3? I think you make a good point that such an upgrade should not be done in a vacuum. The system as a whole needs to be able to use, and handle, the extra output. The first question should really be the one of NEED. For the vast majority of us, there really is none; the 30A generator is quite up to the job. If you think you are one of the exceptions, you should start by actually measuring your output current from your current system. If you don't find that you're already bumping up against that 30A wall, you don't need more. Most of us have the little hand-held DVMs now and there are clamp-on ammeters that we can buy that will measure DC & AC Amps and display them on your DVM. These cost just under $50. Buy or borrow one and see where you actually stand. To make a reasonable measurement, do it at med rpm with everything turned on that you might normally have on at one time. BTW, I was working on a nice old Blaupunkt last week and was driving it from a power supply where I could set the voltage to 14V and monitor the current. It drew 1/4 A when it was playing at a comfortable level and 1/2 amp when it was too loud to enjoy (in a room that is MUCH larger than my squareback.) Don't give us the song and dance about how you have a 1000 W stereo in there so you just KNOW that you need it. I won't be impressed. (Right now my current project is to build two 2.2 Megawatt amps, so nothing you've got really stacks up, by comparison. My amps are just single frequency, 250 Hz, pulsed mode for 50 mSec, but they still take up a couple of very large rooms. The 6 vacuum tubes in the 2 amps consume about 25 kilowatts continuously, just for their filaments, however. Strangely enough, these could still be powered from 35A breakers, although they are 208V, 3 phase.) So start by taking a real measurment, keeping in mind that a peak measurement is interesting, but an average is what you want here. (One of the functions of the battery is to supply the peaks, so that the generator only has to supply the average.) For most of the people out there who have done the conversion, the reward is in just being able to say that you did it. While some of you have certainly needed the increased output, I suspect that most of the upgrades are done because there was a problem with the old system that could have been fixed if they had taken the time to diagnose it. For those of you on this borderrline, I have a FAQ that will let you diagnose and get the most out of your current system. If you're still out there in the 0.1% that NEEDs the extra power, then you need to worry about the WHOLE system. Rewinding a generator for more current is not a simple matter. There is only a certain amount of space for wire so you can't just put in bigger wire; if you put in fewer turns of bigger wire you can have more current at less voltage, or more current at the same voltage but higher rpm. Then you find that the generators are also limited by the brush size and I don't think there is any straighforward way to put larger brushes in your generator, besides, the commutator is only so big, so you're stuck. I've always wondered if there was really ANY difference in the 71 bus generator that allowed it to earn a 35A rating. Maybe they just did something minor to the cooling system to provide more cooling.... Which brings up cooling. Remember that whatever you put in there needs to be cooled. You won't be doing youself any favors by installing an uncooled 70A alternator that dies after putting out 40A for 6 months. You have to provide cooling. Then, in a generator system, the voltage regulator is the thing that draws the line on the current output, so you have to find a compatable VR to go with this. In reality I think that means finding someone who can adjust a 30 A VR to regulate at 35A, because Bosch/VW don't supply the 35A VR anymore. Maybe there is one out there for another car; I don't know. Modern alternators come with internal VRs so they have an advantage here. OTOH, alternator VRs don't monitor current, so you have to make sure that you don't do anything that will suck more from the alternator than it can give without dying. And finally your good question about the wires. Good point. For most of us, this will never be a problem because we don't use all that current anyway. If this was a 6V car to start with, then it already has cables twice as large as the 12V cars, so they will never be a problem. If you have an upgraded 12V car where you can see 60A pulling out of your alternator continuously for minutes at a time, then you may want to replace the wire that runs from the alternator/generator to the VR (unless the VR is internal to the alternator.) For any wires that are after the VR (or outside an alternator with an internal VR) I'd just recommend adding additional wires to your extra loads. The other thing that I would strongly recommend is that you NOT run any larger loads thru your ignition switch. Use the ignition switch to operate a relay instead, so you don't kill that hard-to-find switch. This problem has gotten so bad that I'm thinking of adding an extra relay to my mostly stock type 3s, just to take most of the load off the switch itself. I haven't burned out a switch yet, but I don't want to join those of you who have. ;-) Sorry for the long post.... - Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/