Engine RPM 4+

Worked perfectly. I used this app to check and reset the operating speed of a lawnmower. I found the mower was over 300rpm down on the specified engine speed, which equated to 0.5hp lost. Adjusted running speed to specified value and now it mows like a boss! Cheaper, quicker and easier than buying a tachometer. Don't be put off by the +/-10% shown on the sample page; it relates to an operating mode where the app scans around an expected rpm within a given tolerance range to avoid possible errors due to secondary harmonics, thus providing the most accurate measurement. It is not an error band on the measured rpm. The app can be run in an 'auto' mode if the expected rpm is not known. I recommend this app if you need to measure an engine's speed under steady conditions.

I thought there were no reviews so jumped in. Unfortunately not the magic bullet I wanted but that's not the fault of the app. (wanted to check rpm from some in car race footage). Support was FANTASTIC and helped me find a way to get the answer I wanted as best as possible. It's not a replacement for a tacho or for measuring a rapidly changing RPM. But it is a very clever app and they seem to me to be very knowledgeable on the subject matter. Be realistic and fair and check it is suitable for what you expect to use it on.

Even works in a Renault Clio sport whilst zooming down a Swiss motorway with the radio on, more importantly to me, it enabled me to set up the engine running correctly on my Royal Enfield single cylinder Bullet motorcycle!
Sometimes need to use one of the manual modes, but this does work for me.