I'm changing the alternator on my jdm b16 (sir2) and i purchased a denso replacement alternator. The new alternator has different mounting points than my old one.

Top: old one
Bottom: new denso


I can put the new one in but the belt is too big due to the different mounting points. I'm thinking I can just put a shorter belt on there to solve my problem but I want to know why my old alternator has different mounting point than my new one. Any ideas?

 

My guess is it's because there's a variation between a JDM B16A alternator and a USDM B16A alternator in relation to mounting points. In any case, yes you can just run a smaller belt OR if you can find someone (or maybe find one at the local junkyard) with a USDM B16A, see if you can verify that the bracket that it bolts to is the same length or has the same slot length.

I had a similar problem on my engine and I cut the slot on the bracket to go further back so I could put the proper amount of tension to the belt. Hope that gives you a little insight as to what you can do.

 

I wish I could just adapt the upper bracket to work but it is about a half inch away from it when I use the current belt. Changing the belt is the quick fix but I'm lazy and I don't feel like taking off the other belts to get the alternator belt off.