im buying a new car and i need to know what is the optimum compression it should be holding.

thanks people

 

Optimum.........125 psi on all 6 faces.

Acceptable.......85-90 psi x3 x2.

John ny

 

x6? do i not just pull out the spark plugs and do each one? giving me 2 compression readings?

 

Rear rotor housing leading plug goes puff pufff pufff....puff pufff pufff...puff pufff pufff. 3 even puffs

front rotor housing goes puff pufff pufff...puff pufff pufff...puff pufff pufff same thing 3 even puffs

no weird audible significant gaps and pauses. 3+3 = faqs, i mean 6

Take the check valve out of your comp reader too, or just hold the pressure release. Do not forget to have the accellerator floored or you will have inacurate lower readings (ask me how i flipped out for no reason not knowing that at first)

gl. Post pics of the car.

john ny

 

yeh i got a compression tester, and a guy who owns its said, put it in one of the spark plugs, remove the coil wire so theres no spark, then turn it over. thats all i need to do to each plug, which is 2.

please tell me your method again but slightlllllly more detailed.. i am quite mechanically minded, just never done a comp test before

 

Compression test using a piston engine tester:
1. note battery strength. A weak battery will yield low compression results.
2. Remove both lower plugs and wires.
3. remove EGI fuse from engine fusebox.
4. have a friend floor the accelerator pedal, opening the throttle for more airflow
5. insert your tester into the leading hole
6. hold the valve on the side of the tester open
7. have your friend crank the car over for 5+ seconds.
8. observe the needle bounces. You should see 3 in succession without skips, even bounces, in roughly the 30-35psi range.
9. let out on the valve now, and let the tester reach an overall compression value for all 3 faces(highest of 3 will be displayed). 115+ is like new, 100-115 is healthy, 90-100 is getting weak(1 year or less in most cases) below 90 could blow at any moment.
10. repeat for opposite rotor. Note difference in overall compression between rotors, which should be no more than 20psi max.

im going to do this method, are the compressions in part 9 acurate?