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Location:
Elwood, Melb
Registered:
August 2003
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Something I should already know.
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Mon, 13 September 2004 12:52
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I was just wondering when a compression test is performed, do the mechanics know if its right or do I have to know the compression rates. I wanted to know because Im buying a new car and want it compression tested as well as being told by others.
I also wanted to know the importance of one?
Slap me if you like. 
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Location:
Brisbane
Registered:
May 2002
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Re: Something I should already know.
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Mon, 13 September 2004 13:01
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Healthy compression figures vary between engines, so yeah you've kinda gotta know beforehand.
Having said that, the variation between cylinders is the more important factor. In most cases you don't want the readings to vary much more than 5psi or so.
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Location:
Baulko Hillo
Registered:
April 2004
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Re: Something I should already know.
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Mon, 13 September 2004 13:03
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*SLAP*
A compression test is important to see if your cylinders still have good compression and to see if there may be any leaks, whether it be worn rings or otherwise.
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Location:
Elwood, Melb
Registered:
August 2003
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Re: Something I should already know.
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Mon, 13 September 2004 13:04
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Cheers Norb,
Once I saw your name beside the Tech section I knew all my problems would be solved. So how do I get more chicks  JK
You don't happen to know the compression figures for a RB20DET?
I might go for a quick wander.
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Location:
Brisbane
Registered:
May 2002
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Re: Something I should already know.
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Mon, 13 September 2004 13:08
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| SillyCar88 wrote on Mon, 13 September 2004 23:04 |
So how do I get more chicks JK
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If I knew that do you think I would be posting this crap in the tech section right now? 
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You don't happen to know the compression figures for a RB20DET?
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Nissan crap mumble mumble curse spit. Sorry, no. 
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Location:
Elwood, Melb
Registered:
August 2003
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Re: Something I should already know.
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Mon, 13 September 2004 13:12
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=8.5.1
C'mon Norb don't be like that, I know where your heart lays.
NISSAN JK
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Location:
Brisbane
Registered:
November 2002
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Re: Something I should already know.
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Mon, 13 September 2004 13:16
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Yep, school girls and datsuns for Norbie all the way
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Location:
South Australia
Registered:
July 2002
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Re: Something I should already know.
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Mon, 13 September 2004 13:20
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8.5:1 doesn't really tell you much though...at a guess you would get readings of about 135-140psi per cylinder?
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Something I should already know.
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Mon, 13 September 2004 13:23
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as well as static compression, it depends on the valve overlap.
frinstance, stock cam and compression might be 180psi,
with low overlap and high comp you could have 220psi,
with high compression and large overlap you might have 140psi.
here's an idea  go and look at the manual for the car, or ask a dealer.
as Norbie said, variation = bad.
you could also do a 'leakdown test' (points to google)
Cya, Stewart
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Location:
Elwood, Melb
Registered:
August 2003
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Re: Something I should already know.
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Mon, 13 September 2004 13:30
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Cheers thanks,
I think it's 140psi
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Location:
Tasmania
Registered:
May 2002
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Re: Something I should already know.
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Mon, 13 September 2004 13:30
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I find alot of average cars on the street have right on 150psi.
My 2T-G also has 150psi, but for different reasons.
If you get 150, 145, 80, 145, don't buy the car.
146, 150, 150, 148 is ok, normal.
100, 120, 125, 120 means the engine is worn, may blow smoke, don't buy.
165, 164, 165, 164 means its a newish motor, very good.
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Location:
Elwood, Melb
Registered:
August 2003
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Re: Something I should already know.
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Mon, 13 September 2004 13:49
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Ahhhhh OK like Norbie said, you don't want them to vary much.
Once again thank you all
*Gets down on knees*  JK
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Location:
Newcastle
Registered:
June 2002
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Re: Something I should already know.
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Sat, 18 September 2004 23:46
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ew!
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