NYT article - GM cylinder dropping

[Lester Meeks]

I read that they are leaving both valves closed.  They are controlled well
enough to ensure a full compression happens and stays in the cyclinder and
that the ecu refreshes the cyclinders pressure periodically to compensate
for leak down.  I honestly can't remember where I read this info but that is
my 2 cents.

Les
96 K1500
----- Original Message -----
From: "Eric Deslauriers" <Eric.Deslauriers at oracle.com>
To: <gmecm at diy-efi.org>
Sent: Wednesday, May 30, 2001 3:20 PM
Subject: Re: NYT article - GM cylinder dropping


> I had a 73 Scout II with a 345 where the intake lifter on cylinder 3 wore
> through causing the intake valve to never open. It was amazing how much
oil was
> sucked past the rings when the intake valve didn't open. Seems the rings
prefer
> to keep pressure in rather than vacuum. :)
>
> I don't believe the 2 valves closed effect is what they are proposing due
to
> this effect unless they can time the valve close so that the piston was on
the
> upstroke. I can't see that type of precision with an oil pressure
regulated
> system, and it would certainly be negated based on cylinder pressure bleed
over
> time even if they could do it.
>
> My (poor) $0.02 worth.
>
> Eric D
> 88 K30 Blazer
>
> "Marteney, Steven J." wrote:
>
> > Which would imply it should be just as easy to turn the engine with or
> > without the spark plugs.  As the gas is compressed, the leak down
negates
> > the compression.  No dice.  It doesn't happen that way, at least not
when I
> > build my engine and was turning it on the stand.
> >
> > This will be my last post on this, but in closing.  It takes energy to
> > compress a gas.  Conservation of energy says all that energy will be
> > returned, but it doesn't say in what form.  So to say the MOST efficient
way
> > is to leave both the valves closed doesn't seem right.  There is more
> > pressure at the top of the piston in that case, which means more force
on
> > the oil between the bearing and the rod, which means more "friction."
Now I
> > will admit all this may equate to a neglible difference between the two
> > ways.  Some day I hope to understand it all.
> >
> > Back to GMECM topics!
> > Steve
> >
> > BTW - Thanks for the info.  I really don't want to come off as a total
jerk.
> >
> > -----Original Message-----
> > From: Ron Schroeder [mailto:rjs at bnl.gov]
> > Sent: Wednesday, May 30, 2001 3:23 PM
> > To: gmecm at diy-efi.org
> > Subject: RE: NYT article - GM cylinder dropping
> >
> > At 01:15 PM 5/30/01 -0400, you wrote:
> > >How come it's easier to crank an engine with all the spark plugs out
(same
> > >as valves open) than it is with all the plugs in?
> >
> > At low rpm, the leakdown negates a lot of the energy that could be
returned
> > from the compressed gases in the cylinder.
> >
> > Ron Schroeder
> > WD8CDH
> > E. E. S.
> > wd8cdh at bnl.gov
> > rjs at bnl.gov
> > ron at 112motors.com
> > 631 344-4561 Day
> > 631 286-5677 Nite
>
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