Well there is a direct relationship between the two. As (I believe it was
Ron, a little hard to tell in this message) says, the heat gained by
compression does add a factor which may be difficult to determine. If you
had a perfect seal and turned the engine slow enough so as not to gain heat
by the compression you would see a compression pressure of CR x ATMospheric
pressure.
However, it still is explained mathematically. Search for a reference on
Charles Law which states:
P1 x V1 P2 x V2
_______ = ________
T1 T2
So if you know the compression Ratio and the temperature of the compressed
air you can figure out what the compression pressure will is. Likewise if
you can acurately measure the pressure you can figure out the theoretical
temperature. If you come up with a temperature above 495 degrees you will
have a Diesel motor running on Gasoline.
I'm guessing that the 17 frogeye used in the example includes sea level
presuure of 14.7 PSI plus a generic fudge factor (or maybe it's a real
constant for 11.5:1, I don't know) to account for the increase in
temperature.
All in all, I think it's pretty amazing that an ICE even runs at all.
<dnw>
1972 Midget
1998 Safari
1999 9-3
1964 (Me)
----- Original Message -----
From <John.Deikis at med.va.gov>
To: <spridgets@autox.team.net>
Sent: Friday, November 02, 2001 1:56 PM
Subject: Re: How Much Compression
> Unless I'm missing something here, aren't you confusing "compression
ratio"
> (a mathematical relationship of two volumes) with "compression pressure"?
>
> John Deikis
>
>
> >>Date: Thu, 1 Nov 2001 15:51:12 -0800 (PST)
> >>From: Ron Soave <soavero@yahoo.com>
> >>Subject: Re: How Much Compression Is Too Much?
>
> - --- frogeye <frogeye@swcp.com> wrote:
> > 11.5 x 17(or whatever atmospheric pressure is at
> > your locale) =195.5 It does
> > not compute. Check your gauge.
>
> >>Check the gauge, but again, CR x atmospheric pressure
> IS NOT WHAT YOU WILL SEE. Because the air is
> compressed in a constant volume, it heats up, tries to
> expand (but it can't), so the pressure in the cylinder
> increases, and the pressure read is much higher than
> CR x ATM. If heat were not lost through the metal in
> the engine, it would be way higher still.
>
> =====
> Ron Soave
|