I want start off by noting this cap is the biggest and heaviest I’ve ever seen unlike most caps it does not feel like a toy in the hand . As far as function goes it works great on my application , I also have a 300amp alt and xsD6500 under the hood . Most people that don’t get desired results from a cap because the rest of their electrical system is stock or upgraded with cheap components. If you alternator can’t provide enough juice there is nothing a cap can do so keep that mind when considering installing a capacitor