Re: COMPRESSION TEST -Reply -Reply

From: Robert Lee Cobb Jr. (S0042745@cedarnet.cedarville.edu)
Date: Wed Feb 19 1997 - 20:05:38 EST


> How the He** does someone get 160 psi from 9.1:1 compresion?

I don't know WHY I got it, but I know the guage is fine and I got 160
on 2 different cylinders. NOTHING was below 145. I used the formula
the guy posted about the 29.921 inches mercury = 14.696 psi, and
calculated what it would be at 30 inches mercury (what it hovers
around usually here in the Buckeye state where I live). . and I came
up with a CR of 10.18 using 150 psi average of the cylinders. Let me
ask you guys this. . .has anybody else DONE a compression check on
their motor? If you have and you got less than 130, let me ask you
this: How many times did you turn the motor over when you checked
it? I got 150 average by cranking the motor over about 4 complete
firing series (about 6 seconds worth of cranking). If you only crank
the motor over once, you loose some of your compression in the
guage's rubber hose (the volume of the cylinder is theoretically
increased by the volume of the rubber hose which it now has to fill
up, too). What you have to do is keep on cranking the motor until
you get the maximum amount of pressure in the thing that it will
take. Do this: Have a buddy hold the pressure guage and you get in
the truck and hit the starter (Oh yeah, remove the coil wire first).
Now, explain to your buddy to not tell you to QUIT cranking it over
until the needle won't go any higher. I imagine you guys would get
around the same numbers as me. Otherwise, I'm running a heck of a
lot more compression than I should be. I have no problem with
pinging, either, on 87 octane. Anyway, let's here some numbers. . .

- Rob Cobb 93 V8 LE 2wd

>>> <DesignTech@worldnet.att.net> 2/19/97, 11:20am >>>
yes, some air squeezes by and that is why you can't get the maximum
psi...
right?

how the hell does someone get 160 psi from 9.1:1 CR?

----------
> From: Kukukooter@aol.com
> To: dakota@ait.fredonia.edu
> Subject: Re: COMPRESSION TEST -Reply
> Date: Wednesday, February 19, 1997 12:12 AM
>
> I believe you are measuring the cylinders pressure held by the
rings
using
> the gauge, which is different than knowing your compresson ratio...
> Kuk

 



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