Compression test

[jacobsen]

I've done a compression test on my 1.8 and I want to check the procedure to make sure my readings are correct. When doing my test I am removing all the spark plugs, unplugging the coil packs and injectors, removing the throttle body from the intake manifold, oil cap off and dipstick removed. Is this the correct procedure? I cranked until the pressure tops out. And could a bad turbo cause low compression readings? Could a thermostat that is stuck open cause low compression from motor not heating up?

Sent from my SM-G920V using Tapatalk

[diagnosticator]

Your procedure is OK, but the throttle body doesn't need to be removed, just hold the throttle pedal to floor while cranking the starter. The oil fill cap and dipstick are left in place as well, nothing to be gained by testing compression with those items removed.

A bad turbo won't effect static compression, but the boost pressure developed effects the dynamic compression when the boost pressure is added to the atmospheric air pressure in the cylinders when the valves are closed and the compression stroke begins.

Engine coolant temperature does not effect compression pressure significantly.

[tHatOne guY]

In case you didn't have these, right out the Bentley but converted to Psi instead of Bar.

Should see no more than 43.5 psi difference between cylinders.

New engine will read between 130.5 to 203 psi.

And engine wear limit is 101.5, oh and 86 degrees F oil temp.

[jacobsen]

In case you didn't have these, right out the Bentley but converted to Psi instead of Bar.

Should see no more than 43.5 psi difference between cylinders.

New engine will read between 130.5 to 203 psi.

And engine wear limit is 101.5, oh and 86 degrees F oil temp.

New is between 130 and 200? That seems like a lot of variaton?

Sent from my SM-G920V using Tapatalk

[diagnosticator]

New is between 130 and 200? That seems like a lot of variaton?

Sent from my SM-G920V using Tapatalk

No cylinder's compression test should be lower than 44 psig below the highest compression cylinder.

New engines are not broken-in yet, meaning the piston rings have not seated fully, among other things, and that results in lower compression compared to an engine with 10K miles on it since new.