Compression Tester
 

What are the differences between piston and rotary compression testers? I have a buddy who has a piston compression tester and this is something I wouldn't use frequently so why spend the money on one for use maybe twice.

Tks.

A piston engine compression tester only shows the peak compression for one chamber. To measure rotary compression, you either need to use a rotary tester, which records all three pulses, or remove the valve thing from a piston engine tester so you can at least watch the needle and estimate all three pulses.

Great thanks.