I had high hopes for these devices, they were exactly what I needed. I am an experienced electronics engineer, I connected them exactly according to the instructions. works but failed a few minutes after hooking it up to my dyno. Blank display, no operation. So I replaced it with a second unit, which worked great on my dyno for a day, but once installed in the chassis it should be. failed like others. Blank display, no operation. My experience seems to be common among those who leave reviews. These cheap units are cheap for some reason, very poor quality, they are very unreliable. Save money by spending a little more and buying something that works. You will only throw away your money by buying them.