Thanks for taking the time to draw that up.!
The way my sensor works is that at low engine RPM it outputs a sine wave at low voltage (say +/-4v peaks) but at high RPM those peaks are close to +/-50v. Although the voltage divider will reduce the 50v to 4.55v will it not reduce the 4v to something like 0.35v?
Also this isn't s square wave output to the Arduino?