r-james@tamu.edu wrote:
> ...and Bob Allen replied:
>
> >Yep, motor should be warm, throttle open, jam something under the
> >dampner pistons to admit lots of air. It's good to see even pressures
> >across the board but those numbers aren't much more than 7 to 1
> >compression.
>
> (First I think Bob has misplaced his calculator)
Well then you can just lick the hair off the balls of my syphlitic dog.
Opps! P-C Alarm! \h\h\h\h\h\h\h\h\h\h\h\h\h\h\h Shoot. Too late.
> The question is what pressure should be seen for a given
> compression ratio?
Ain't that easy. IMHO these are the facts:
1.) 140s is close to what the silly TR6 is and it has 7.5:1 compression.
2.) It fits with the known compression values off other engines that are higher.
3.) If is pretty close to the little chart printed on the face of my compression
guage.
> <snip the mathmatical dweebisms>
>
> How have I gotten so close to the "right" answer
> without even propping open the throttle?
Because that is what you were looking for.
I tried, once, to use a claculator to take a compression test but the huffin'
and puffin' kept foggin up the display and I couldn't read the numbers. Finally
I started to notice what appeard to be surface rust so I dipped it in Naval
Jelly (I'm blessed with a "Big In-ee") but then the case got all soft. That did
make it easier to jam into the spark plug hole but didn't improve the accuracy
one BCH.
Okay, okay, to be serious, IMHO, blowin' in the 140s is around 7:1 and into the
200s is crossing over 10:1. Maybe your calculator can interpolate values in
between. It's more important to be even than to be high but "high enough" should
be in the 160s.
Something else to figure into your calculator is that compression pressure often
drops from front to back. Why? Cooling differences? Heating the guage? Oil
pressure? Naw. You run the test from front to back and the battery gets tired
towards the end. Engine ain't cranked as fast and pressures go down. Go find the
emprical equation for that one.
--
Bob Allen, Kansas City, '69CGT, '75TR6, '61Elva(?)
"There is a difference, sometimes, between what is legal and what ought to be
done" -- Bill Clinton, March 7, 1997
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