Alternative altermator

[Mark Holden]

Some months ago I mentioned that i was looking to adapt a 125A alternator
from the 95-97 Maximas to my SR20DE.

Well, it's done, and here's what I learned.

There are two alternators used on the 95-97 Maximas, a 110A unit and a 125A
unit, both I believe are Hitachi made.  I expect that everything I learned
about the 125A unit applies to the 110A unit also, but I can't say for sure.

First, a couple of links to some data sheets:

The alternator for the 91-94 SE-R/NS2k and 91-93 G20 -
http://www.vicic.com.tw/alternators/gva8010.htm

The alternator for the 95-97 Maxima and 96-97 I30 -
http://www.vicic.com.tw/alternators/gvhn11250101.htm

The differences are fairly slight:
 - 1mm difference in the radius between the center line of the pulley and
the pivot at the block
 - 2mm difference between the center line and where the adjuster bolt
attaches.
 - The pulley on the Maxima unit is 63mm in diameter and the SR20 unit is
70mm.
 - The connectors are different
 - The Maxima unit lacks a nice threaded hole to attach the ground wire
 - The post of the output on the Maxima unit is larger in diameter.
 - The pivot points at the front of the alternator is 13mm on the Maxima
unit rather than the 25mm of the SR20 unit.

What I did mechanically:
 - Swapped the pulley from the Sentra alternator to the Maxima unit.  It's
handy to have a small impact wrench for this because then you don't have to
clamp the pulley to remove the 24mm nut.  If you had to clamp it, you'd want
to pad it well to avoid damaging it.  My HF 18v unit that doesn't have
enough torque to break loose a lug nut was plenty for this.
 - The unit will slip right on, but because the pivot point at the front is
12mm thinner, there will be a gap.  What you want for this is a 12mm spacer
with an inside diameter of 10.5mm or greater.  I still need to find
something like this, I just put a nut in there as a temporary fix.  There is
a sleeve that came installed incorrectly on the alternator I bought, that is
on the other pivot point.  I had to tap it into place with a small hammer
(or whatever was handy, probably a wrench :) ).  Because I used the nut
instead of a spacer, I had to take off the bracket at the front of the block
that holds the front alternator pivot in double shear and then reattach it
after the bolt was through.
 - In order to get the adjustment bolt attached to the alternator I had to
loosen the adjustment bracket where it bolts to the block, get the adjuster
attached to the alternator and then re-tighten the bracket bolts.  This is
because of the slight difference in the diameters of the alternators, and is
only an issue at the far end of the adjustment range.
- there is a 0.3mm difference in the location of the pulley with the new
alternator, however, in practice, it doesn't seem to make any difference.

What I did electrically:
 - Because this unit puts out such a higher amperage (my specific alternator
bench tested at 158A peak output!), I added a 4ga wire that runs from the
alternator to the battery.  I left the original wires in place (one runs
straight to the battery, the other to the main fuse/relay panel by the
battery), but had to crimp new rings onto them to fit the larger post on the
alternator.  I also ran a 4ga 32" long pre-made negative cable to replace
the stock ground.  Because i will be relocating the battery and I have a
deep-cycle Optima bluetop, I just attached it to the extra terminal on the
battery for now.  The battery will move, and in it's place will go a
1-into-4 distribution block.  If the battery was staying and a normal sort,
I'd look at one of those battery terminals that integrates a distribution
block.
- Because the new alternator lacks the threaded hole for the ground, I took
loose one of the nuts on the alternator housing (probably right where the
regulator is) and attached it there.
- I pulled a spare Maxima alternator at the junkyard, and took the wiring
harness with it.  I cut off the last 6" and made a pigtail with Anderson
Powerpole connectors.  You could also splice directly into the Sentra wiring
harness, but I wanted to be able to swap back to a stock unit quickly (this
is a race car, so things like that happen).  Each alternator has an S and an
L terminal and there's a diagram right on the alternator showing which is
which.


That's it.  Works like a champ!

The specific alternator I used was a brand-new (not rebuilt) unit made by
NSA (ALT3205) bought through Rock Auto.  The build quality seems quite good
for a low cost unit.

-- 
Mark Holden
meh710 at gmail.com
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