Comments by "volvo09" (@volvo09) on "THIS is the ULTIMATE scan tool for DIY mechanics on a budget" video.

  1. It's called a "relative compression test". It doesn't show psi. It monitors battery voltage vary rapidly during an extended period of cranking to sense low compression cylinders. (With new cars maybe the crank sensor speed too...) Bad compression in one cylinder will have higher voltage or a faster crank speed as the piston goes up. If every cylinder is equally bad, the result won't show anything. But if you have a burnt valve some other issue that reduces compression on one or two cylinders, you can see the bad cylinders on a percentage chart.
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  2. Yeah that's a good price for a bi directional tool.
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