jhaag Posted July 7, 2003 Share Posted July 7, 2003 There are a variety of different amp ratings for alternators and common sizes seem to be anywhere from 60 to 100 amps. Some of the performance catalogs advertise alternators as high as 140 amps. As someone not very well versed in electricity, I've often wondered, but never asked, what the pros and cons are to larger amp ratings. Over the weekend, I saw an article about a race truck built for Baja off road racing that had a 325 amp alternator. Hmmmmm.....now I've got to ask. Does a higher amp rating mean it's going to take more horsepower to run? Does it mean it's going to be significantly larger in size? I'm guessing large amp ratings mean the alternator will cost a whole lot more. Why would a off road race truck need such a high amp alternator? I'm guessing that serious racers would not get into the 'bigger is better' rat race unless there were good reasons. Thanks! John Quote Link to comment Share on other sites More sharing options...
snork Posted July 8, 2003 Share Posted July 8, 2003 im not good with electricity either, but i can answer one of your questions. they run such a big alternator for some of their much needed excessories ( off road lights, winch if they have one, communications, ect.).im guessing mostly lights is the reason for the big alternator. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 8, 2003 Share Posted July 8, 2003 Yes they run those big alternators for their offroad lighting. 325amps is a lot of lights! The biggest problem I've found with low output alternators is that they don't supply much current at idle speeds. This means when you stop at a street light for example, your headlights may dim. (anyone who has a Z has seen this!) You could spin the alternator faster with a smaller pulley, or go to one that makes more current overall. I believe the relationship between the horsepower to drive the alternator and its output is pretty linear. Regardless of your alternator output, the draw from your car will be the same. ie: if you need 40amps to run your car, you'll need 40 amps to run your car whether you are using a 45amp alternator, or a 130amp alternator. In each case, your car will get the 40amps, so a 130amp alternator will gain you nothing, except that it may produce more current at idle, which may be just where you actually need that boost... Quote Link to comment Share on other sites More sharing options...
spotfitz Posted July 8, 2003 Share Posted July 8, 2003 Think about what is going on when you pull up to a red light and it's raining and at night. You need alot more power to keep the car running along with the wipers, lights and still keeping the battery charged. I've had my tape player slow down before. Sounds pretty funny at the time, but it also got me worried. If you're drawing the ? amps for idle, what are you drawing with the other necessities? With a 60 amp alt you can easily max that out pretty quick. Thats not to mention all the poor connection in our Z's and how there routed. Not that it's ever a good thing to over-come the power loss through the connections with a high out-put alt. but I have found less problems with my z when I had the 100 amp alt. compared to the 60 that was in it. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 8, 2003 Share Posted July 8, 2003 The 45amp ones in the stock 240's are pretty lame too... Quote Link to comment Share on other sites More sharing options...
zcarnut Posted July 9, 2003 Share Posted July 9, 2003 Installing a higher output alternator is an excellent upgrade as the early Z cars had a minimal sized one. However a few remarks here: One issue with the larger amperage alternators is that the electrical output terminal on the alternator is usually larger so it won't connect to your stock harness without replacement of the corresponding connector. You should also consider increasing the size of the wire between the alternator and the battery. It should be rated for the increased alternator current. I have seen some vehicles with 120+ amp alternators that used a battery-to-starter sized wire between the battery and alternator. Some “high output” alternators just use a smaller diameter front pulley so that the alternator spins at a higher rpm (alternator output is a function of it’s speed). But this means that the alternator can reach speeds over 20,000 rpm(!). This puts additional centriphical stress on the armature windings and reduces the life of the alternator bearings and brushes. Needless to say, alternator balance becomes very important. Quote Link to comment Share on other sites More sharing options...
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