This is noobish but users on here keep refering to compression so what exactly is compression?, what does it do/is it? how/where do you check compression, and how much compression do our car suppose to have? any help would be appreciated.

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compression

n 1: an increase in the density of something 2: the process or result of becoming smaller or pressed together: "the contraction of a gas on cooling" 3: encoding information while reducing the bandwidth or bits required 4: applying pressure


definition courtesy of dictionary.com (yes my spelling is bad)

for an engine, when the gas and air are drawn into a cylinder, the intake valve(s) close and the piston starts to go up, since (in theory) there is a complete seal, the gas and air have nowhere to go so they are compressed into the tiny area (compression chamber) where hwen the piston reaches a point just after TDC they are ignited...


ok... measured in (i'm assuming PSI) from the factory your engine should be in the range of 180-220... slight varience in the reading is ok, but anything over 10-15 i'd look into...

for the test there is a writeup on the main page... but i'll try to describe how it works (even though i've never done one, i'm afraid to see what numbers i'm getting) you remove your spark plugs (if you want, the wires also so they are not in your way), disconnect the ignition and disconnect the fuel pump/injector relay(s) and start cranking.... engine should be warm to begin with so everything had a chance to expand... keep cranking until the needle stays steady at a certain point, that is your compression... oh yeah, you also need to put the compression tester in the spark plug well, thread it in.... don't get the rubber ended ones, the aren't as good.

hope that helps a bit.

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-Ryan

basicaly it's a ratio of how much the air is compressed preferably before ignition

*Skrilla
"Honest officer, I thought you were trying to race me"
Talon: 1st 2.4L
'97 Prelude
'04 350Z

Originally posted by etx
Good luck man! Project 'STFU Brian your talon is dead meat' should be on it's feet soon!

so if it is higher then what it should be or lower then it should is there something majorly wrong?

nothing wrong with being higher... as long as they are all basically the same, or near each other.... higher compression will result in more power...

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-Ryan

As gas is compressed, it becomes hotter and more unstable. Considering there is fuel mixed in with the air, if you compress it too much and it gets too hot, you get ping, predetination, generally psychotic behavior.

Turbos force more air into the same space, effectively increasing the compression (not the compression ratio I wouldn't think) and that is why you need to add more fuel when you turbo, so you don't lean that shit out too much and get predet.

yeah, as DR1665 said, detonation is bad!!! if you are getting it, go to a higher octane gasoline

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-Ryan