compresion test

[4g63gst20]

hi again guys, today i just ran a compression test a few minutes , and this are the readings , starting from passenger side to driver side, if that helps, my engine is a 420a, 120-110-110-150, so my question is are this numbers to low? i read a post a couple weeks ago about pouring oil in the cylinders, let me know if doing that would help a little, i'd try that later, thanks

[kjewer1]

Those numbers are low. Is the battery charged? Throttle open? It might suck if those numbers are real.

[Gsx_hooptie]

The compression should be 170-225psi, with the service limit at 100 psi (info specific to 420a). Those numbers do suck. More info can be found at http://www.dsmgrrrl.com/FAQs/compression.htm

A little oil in cylinders with low compression (note: not "pouring" ) will tell you if the low compression is because of bad rings. The above site explains how to do a wet test, if you want to try that. If this isn't the case, you could then do a true leak down test to figure out where the compression problem is.

I doubt the problem is the rings when compression is bad throughout. My guess is mechanical, but that's Kevin teritory. First, make sure your readings are right. See if you followed the procedure on the page I listed, including the things Kevin mentioned. Hopefully that's where the error is

[4g63gst20]

thanks for the link, i'll make sure that the battery is fully charged, i'll gladly take it for a hard drive right now, that's what it says in the page, lol.

[4g63gst20]

i just came did another compresion test, and here are the new readings,160-150-145-150 probably the battery,

[kjewer1]

A quick note about the "wet test"...

The turbo cars have dished pistons. Not sure if the NTs do, maybe not, since compression is higher. At any rate, using on a dished piston motor is useless. The oil will just sit in the dish, and get no where near the rings. The compression test results will still go up though, because filling the dish with oil makes it smaller Increases static compression ratio.

Good to see the humbers change quite a bit. Unlikely to be a real problem, maybe just battery like you said. If this is cold, a warm motor helps a bit too.

[MoozillaGSX]

i looked around but i didnt get ver far, i was woundering if some one could post what a compresion test would look liek on a car thats running good. and then maby on one thats running bad if posible. or if theirs a thread or link or osmehting i didnt see that some one could link me to.

i want to do a compression check soon but it would be nice to have somthing to compare it to when i do it. thanks.

[l_eclipse_l]

Originally Posted by MoozillaGSX

i looked around but i didnt get ver far, i was woundering if some one could post what a compresion test would look liek on a car thats running good. and then maby on one thats running bad if posible. or if theirs a thread or link or osmehting i didnt see that some one could link me to.

i want to do a compression check soon but it would be nice to have somthing to compare it to when i do it. thanks.

I'm pretty sure 190 across the board, give or take 5 psi, is ideal for our cars.

[MoozillaGSX]

kool. also if say 190 is ideal......should they all be at the same PSI ??? what if its like this. 190-185-170-180 ? is that bad ?? or should it be more like 190-185-187-189 "???