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i did a compression test and got 120 all the way accross its a d16y7 with a z6 head has vitara piston head is stock with a autozone head gasket is this good to boost or not really and yes i did it on wot
 

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yeah i guess thats low enough for boost? if it was me i would be looking for closer to 180 psi accross the bord. then just run less boost from your turbo and make the same power.. its funny how turbo guys always dumb down a motor to boost it in low boost/power applacations(under 14psi or under 250whp) when if they build an efficient motor they woudnt need so much boost to make the same numbers.

like lets say same turbo, same motor, just different comps.
8:1comp @ 10 psi lets say 200whp
10:1comp @ 7 psi lets say 200whp and faster spool times and when not in boost the car will drive alot better

a 9.5:1 motor i would have no problem calling a low comp motor. hell some mazdas have 14:1 from factory. and kia's with 11.5:1 in there every day cars.

on my na build i wrapped the gage past 300 psi when i did a hot compression test lol, cold she was 275 avarge with 5 psi difference
 

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ok well now i put oil in and did the test and got 210 does this make sense
you turned the motor with the started with no oil in it? and ill bet you put the pistons in dry so the oil helped seal them up and was the car hot this time and not last time?
 

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yeah it was hot both times but one of the two time it didnt have oil. so every time you do a comp test you must have oil in piston right
 

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yeah it was hot both times but one of the two time it didnt have oil. so every time you do a comp test you must have oil in piston right
ohh i thought you ment you didnt have oil in the block. like no oil in the whole motor. no you dont put oil in the spark plug hole every time you do a comp check. thats cheating because the oil takes up space with rases the comp and it will seal bad rings. so its a false reading.

download an oem service manual for your engine and read how to do a comp test, is going to be your best bet to get it right
there are so many little things you learn when reading that and how to do all the tests and what to look for and what to check its really worth it
 

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so since i put oil in the spark plug whole that means i have bad rings right. reason why i ask is with no oil i have 120 with oil i have 180
 

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so since i put oil in the spark plug whole that means i have bad rings right. reason why i ask is with no oil i have 120 with oil i have 180
when you put oil on your pistons and then the pistons are at TDC the oil is filling the combustion chamber making less room for air so the compression is up. if you put an ounce of oil ill bet you will get like 400 psi. and if this is a new build ill bet the rings didnt seat yet, so dont worry about that. just break the motor in and see where you are
 

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Your compression sounds about right. My vitara build had 115 all the way across the board. If the compression wasn't consistent from one slug to the next, then I'd start to worry.

Also, adding oil can change the numbers but it really depends on how much you put in there. If you're only adding a cap full and they're going up that much, it could be a ring issue BUT you've got to remember that you want to do the test hot and on a motor that's already been broken in, I.e. your piston rings have already seated against the block, otherwise you're just getting false readings.
 
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