110 Amp alternator - will it cause problems?

[ragtoprex]

Thinking of swapping out my 1988 stock alternator on my vert for a rebuilt one (RX7) that can put out 110 amps - will it cause any problems or mess anything up with the cpu / engine management computer or wiring?

d.yerke@hotmail.com

[toplessFC3Sman]

A 110 Amp alternator should be fine, as long as you wire it properly.  Alternators are a bit more complicated than the single-wire affairs that they used to be in the 70's.  You really need to get a wiring diagram from the donor car to trace where each is connected to; generally they have a "sensing" 12V that needs to be connected to a switched power and a constant 12V from the battery, in addition to the thick, charging terminal.  There's a bit of info on RX7club.com in the 2nd gen section for wiring a 130A alternator from an FD into both the S4 & S5 FC's.   I've done this, and it's been going strong for 5-6 years now.

[ragtoprex]

Thanks for the info...this is supposed to be a rebuilt rx7 alternator - upgraded to 110 amps.  They didn't mention different wiring - but said it was specifically for a 1988 rx7.

[toplessFC3Sman]

In that case, you shouldn't have a problem with it.  If its just a re-would S4 alternator, it'll be plug & play, with a bit more capacity.  The charging wire is thick enough that any additional current draw won't be a problem.

[ragtoprex]

Thanks thats what I was hoping...............

[ITSWILL]

I know this is an old post but as I was reading this it got me thinking.  If you are going to run a higher rated alternator, you should run an additional charging wire to keep up with the extra amperage. Additionally you would need to up the main fuse to handle the extra current.

[~Groll69~]

That is actually good thinking.  The original charging wire isnt very big at all, so i could see how the extra amperage would affect it negativly.

[toplessFC3Sman]

The original charging wire isn't overly big, but it doesn't have to be, since it is all of 3 or 4 feet long, so the total resistance is not very large.  Even with a larger current output, the stock wire is fine (until you start doubling the current output anyway), especially since you're so rarely drawing the full capacity of the alternator.  The bigger problems are the connections, which can deteriorate due to oxidation etc.  As long as they're nice and clean, and you use a bit of di-electric grease, the stock wire will be more than adequite

[ITSWILL]

I calculated that for 110 amps, 14 Volts and 2 meters you would need an 10mm ^2 or 8 gauge wire.  With that said I think the stock wire is is about 8 gauge.  I would er on the side of caution and add another wire or use a larger gauge wire.

There is a good reason Mazda used 2 wires on my 20B alternator.

[~Groll69~]

You are better off using a larger guage wire rather then two seperate wires.  Electricity is going to travel the path of least resistance.  The more electricity on one wire the greater it will heat up cuaseing resistance and possibly burn out.  A second wire is good for a fail safe, but you are better off using the larger guage wire.