So I did a compression test today and I guess I kind of did it wrong but I want to see what your impression is of the results.

Engine was cold.
Elevation 200 feet.
Throttle body was not open (I didnt hold the gas floored)
Numbers 130-135 all cylinders.

1. Is this Good/Bad?
2. Does compression go up or down once engine is warm?
3. What does Wide Open Throttle do? Higher or lower compression?

Thanks for your help.

 

Depending on your altitude, these are not bad numbers. Generally I have seen on my own 86 that cold versus hot, cold numbers will be about 3-5 psi less. Wide open throttle is the norm but don't remember checking to see what difference there is between closed throttle or wide open.

 

Anyone else know what wide open throttle does?

 

You need the engine warm with the throttle wide open. Same # revs per cylinder.

The test you did with the engine cold and the throttle closed is not valid.


TonyG

 

Allows air to enter the intake system without obstruction from the throttle body plate.

 

... because the engine compresses air.

The more air it can compress, the higher the compression reading. Thus no obstruction in the airway, the more air the engine can draw in, the more it can compress, the higher the compression reading.


TonyG