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Discussion Starter #1 (Edited)
Hi,

I own Suzuki SX4 Sedan (2012 - J20B engine), automatic transmission.
I'm interested how much it needs to be compressed for a new car just bought?

I am confused because some people say 180 ish and some people say 160 ish
and it also depends on the sea altitude when compression is measured.

Supposedly not the same to measure on 3.500 meters sea altitud or 300 metars sea altitud. If so, what is the difference in ish?
 

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so..at what altitude are you? and where ?
at 3500m (11500ft) , air pressure is 9.6 psi....instead of 14.7 (absolute) at sea level.
 

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Discussion Starter #3
so..at what altitude are you? and where ?
at 3500m (11500ft) , air pressure is 9.6 psi....instead of 14.7 (absolute) at sea level.

I'm at a altitude of 400 meters. My car has 82.000 mile and its compression is 160 psi.

That's why I'm interested in what compression has a new car just bought.
 

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I'm at a altitude of 400 meters. My car has 82.000 mile and its compression is 160 psi.

That's why I'm interested in what compression has a new car just bought.
is that cold? hot? and fully charged battery and WOT? sounds reasonable if thats cold with that many miles
 

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Yes.
Take all 4 spark plugs out, test compression on all, if they are the same within little margin, all is OK.
Now if we have to go by the numbers…at 400 meters, absolute “normal” atmospheric pressure (actual value varies a little) is 14 psi. Compression ratio is 10.2. Isothermic compression without losses would bring this to 143 psi absolute, 129 gauge. But rapid compression approaches adiabatic, meaning an increase in temperature, hence pressure. The engine condition, temperature and cranking speed and atmospheric air temperature do have an effect on this and this is why those variations may bring different results, like something similar on all cylinders probably between 160 and 180 gauge….but predicting an exact value is futile.
As long as all cylinders all have a value close to each other in the above range, like the 160 you mention, it is OK….
 

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.. and does anyone know the answer?
the figures are ok, its the difference between them thats more of an issue, you just say "160 psi" but don't list each cylinder.

15 psi or more difference between cyls requires further investigation

As long as battery is fully charged overnight before hand, and wide open throttle with all the other plugs removed then figures are ok. Do a cold test, dry and wet (teaspoon of new clean engine oil down the cyl just before the test is a "wet" test) and note readings.

Hot tests are not all that good, and quite often inaccurate.
 

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This thread has run it's course.

If a tangible problem actually exists, provide all of the amplifying data (with symptoms and issues noted) in a new thread. :)
 
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