compression test, is this good?

[duty780]

I just got a compression test done on my sr20det. The intercooler piping was still on, even on the throttle body, and all the spark pugs were taken out. I got 130 dead even on all the pistons. If i recall, they are suppossed to be 155. Did i get 130 all across because all the spark plugs were out instead of one at a time, and because the intercooler piping was still on even with the gas all the way in? Thank you guys.

[assassin7420]

was the engine warmed up with a fully charged battery?

[Rucca]

your readings will not differ (at least not noticeably) with piping on and off. plugs in other cylinders have no effect on the current cylinders compression either.

the only way your results would be low would be if your engine was cold or the throttle plate was not opened fully.

[duty780]

the engine was warmed, but the engine cranked a bit weak. am guessing since the battery is in the trunk.

[Rucca]

battery in the trunk won't cause a weak cranking, but a low battery will. you need to have a battery charger hooked up while running a compression test. each revolution of the engine draws power from the battery and results in a weaker subsequent crank. without a battery charger hooked up you will get a low reading

[ZiG]

If i recall, they are suppossed to be 155.

I'm pretty sure you recall wrong. 155 is the dead MINIMUM they should be. 130 means it's rebuild time.

[duty780]

I'm pretty sure you recall wrong. 155 is the dead MINIMUM they should be. 130 means it's rebuild time.

this is an sr20det not a ka24de.

Okay fellas, so my reading should increased if i cranked faster?

[schanne]

how many times should you let the motor turn for your reading though?I want to say I did mine @ 4 turns and got 156

[s13_maJiK]

I'm pretty sure you recall wrong. 155 is the dead MINIMUM they should be. 130 means it's rebuild time.

Close but the FSM says STANDARD is 155 and the MINIMUM is 128, and the limit difference between each cylinder is 14psi

Yea make sure the car is at running temp, and the battery is charged, because if the battery isn't fully charged you won't have as much cranking power so your compression will be lower, also by having the car at operating temp the rings and pistons will be fully expanded and form a better seal than when there cold, and one more thing if you still get lower reading after you do this its time for the wet compression test. A wet compression test is adding about 2 squirts of oil into the cylinder. If your readings are much higher then you might want to start looking at some rings. But it sounds like your in specs so its your call to what you want to do.

[AZ89two4Tsx]

wrong topic. oops. But thanks for the info anyways.

Modified by AZ89two4Tsx at 6:53 PM 4/9/2008
Modified by AZ89two4Tsx at 6:54 PM 4/9/2008

[Rucca]

First off, I don't know what the standard should be but if the previous post is true and 155 is the standard (i.e. perfect compression) then 143 on all cylinders is excellent. You should have no problem running a 200hp setup. I personally would perform a leakdown test as well, but as long as your car isn't consuming any fluids you can be pretty sure that your engine is in good shape.

On a side note - near as important as getting compression close to the standard is having equal compression on all cylinders. I.E. I would rather have an engine in this case with 135 on all cylinders than 155 140 158 139.

[s13_maJiK]

true that i'd do a leakdown test as well, and a running compression test