electrical and ignition 35Amp To 95Amp Alternator Swap (Ebay Vendor)

[RAS-2002]

I'm considering an alternator upgrade for my non-tii '72 2002, from its stock 35-amp alternator to a 95-amp unit, and I found the following offer on ebay.   Has anyone had any experience with this ebay vendor?  Looks like this is a simple (read: idiot-proof) swap-out:

 

http://www.ebay.com/itm/BMW-Alternator-2002-1966-1976-95AMP-DROP-IN-HIGH-AMP-Generator-/350879089998?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3ABMW%7CModel%3A2002&hash=item51b206054e

 

Also, from numerous searches, it appears that there are many advantages in upgrading to a higher amperage alternator.  But now I'm curious: are there any downsides to the conversion ?

 

Thanks,

Bob

(Schatzi is still hibernating in the garage; she's waiting for her NY roads to be salt-free...)

[esty]

https://www.google.com/search?q=site%3Abmw2002faq.com+alternator+bnrparts&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

[jimk]

Search for BNR, there's lots of stuff.

Search for BNR, there's lots of stuff.

[John_in_VA]

Just 2 of the 22 results from using the search tool with "bnr" and "alternator:"

http://www.bmw2002faq.com/topic/67658-high-output-alternator-question/?hl=bnr+alternator#entry934260

http://www.bmw2002faq.com/topic/111910-85-amp-alternator-a-good-idea/?hl=bnr%20alternator

Edited January 17, 2014 by John_in_VA

[RAS-2002]

Once again, thanks. You guys rock.  It didn't occur to me to search specifically for 'BNR'.

So, like everything, it appears that there's pluses and minuses for buying from them.

Just gotta tally 'em all up and figger out if there's more pluses than minuses....

 

Much obliged.

-Bob

[hchueh]

It is a drop-in (the whole alt is ever so slightly thicker but otherwise identical) -- I supplied my original core and they rebuilt that to "like new" (I asked for an external voltage regulator version because I wanted to retain it). I found their customer service so far to be quite good. It definitely produces more amps; there are a few caveats:

 

1. If your problem is too few amps at idle (lots of stop and go traffic with high load), you may want to use a slightly smaller pulley.

2. If your wiring is suspect (high resistance due to internal fraying, corrosion, etc etc) then the benefit may be limited -- if you are having poor charging without serious load (A/C, custom stereo, etc), I'd recommend tackling the wiring *first*, then trying an upgraded alt, because the original *should* be fine in a stock car, assuming wiring and alt all in top notch condition.

3. It is still possible to overwhelm the BNR "85amp" alt if you have A/C, lights, stereo all going and you are at idle (realistically this alt is prob more like 55-65amps when warm) -- to the degree you need a killer alt, check out rushps.com; won't quite be drop-in but will be the best you can get.

 

Good luck

[JohnS]

I've purchased several items from BnR and have had no issues with any of the the parts (3 starters, 3 alternators) or with the vendor.  One thing I would recommend is that you keep the pully from your old alternator.  Most of the alternators that BnR sells have a new smaller pullys that might require you to use a different size fan belt in order to get it tight.  I just swap the original pully onto the new alternator so that my fan belt remains standard.

[HBChris]

I had great service as well for their Alt in my coupe but I needed to swap the pulley, it was a tiny bit thicker which caused it to interfere with the PS pump belt. Swapping pulley was easy.

[Kidasters]

I had the BNR unit.  Like you've read, at night, at idle with A/C running (and yes - you need A/C at night in Houston) - dimming lights.  So, I went to the guys at Rush and ordered a 119 amp alt.  Small pulley.  It was drop in.  If I wanted bigger - they could do it, but it wouldn't be drop in.   I'm happy with the 119.  Had to run some extra wiring so I wouldn't melt the stock harness, but that's OK.  Rush won't steer you wrong.

[Chris_B]

One thing to keep in mind is that you can't produce more power without consuming power from your motor. I have an 80 amp alternator from an E30 318 in my 02 (w/internal regulator) and it has been a bit tricky to keep the belt adjusted properly- tends to slip with the motor is cold. This is in part because it take more power to spin up the alt than the original 45A or whatever it was that came with the 02. Bottom line, you can't make and consume more power without contributing more power from somewhere else. Likely your fuel mileage will suffer to some extent- I have no idea how much, since my 02 is not a daily driver and I have too many other things going on to reliably track that.

[mikesmith]

The parasitic cost of running a more capable alternator is very low (the fresh bearings probably offset it), so the extra fuel cost you pay is going to be related to the load you place on it rather than just because it's rated higher.

 

Heat doesn't affect alternator capability (at least, not the heat that an alternator should be seeing in your car); as has been mentioned above mostly what matters for a daily driver is the current capacity at idle. A smaller pulley on the alternator is one way to raise the available current at idle (since it spins the alternator faster); if you swap back the original, larger pulley you're effectively derating your new alternator.

 

A comfortable rule of thumb is to assume that you should limit your at-idle current load to about 50% of the alternator rated current, i.e. for a 95A alternator don't count on running more than ~50A of stuff all the time. 

[rover1]

i think what mikesmith is saying is that your alternator might be rated at 95 amp but thats not really the what your electrical system is going to recieve

[hchueh]

I believe the rating on an alternator is the max output in amps. The output is related to how fast the alt is spinning. Typically max output will occur when it is really spinning with engine revs at least 2500-3000 (output will plateau at some point). At idle with rpm at 900-1000 the output is significantly lower.