[Diy_efi] Using EGR as poor man's CR control ?

[Gerald Gnitter]

I suppose you have taken the density of the gas into
consideration in your forumula?  
Basic physics tells me that higher temperature = lower
density.  
What is your rationale?

I appreciate your vantage point.

GG

--- Greg Hermann <bearbvd at mindspring.com> wrote:
> At 10:02 AM 12/16/02, Gerald Gnitter wrote:
> >It's simply a matter of dilution of the intake
> charge
> >thereby reducing the amount of cylinder pressure
> upon
> >ignition.  Certainly spent exhaust gasses re-cycled
> >into the combustion chamber will be slightly more
> >compressible than will the same volume with only
> fuel
> >vapor and air, but the delta would be literally
> >un-measureable.
> 
> April fools' day again ??
> 
> The hotter the gas, the more work it takes to
> compress it by a given
> mechanical ratio.
> 
> The higher the molecular weight of a gas, the less
> its temperature will
> rise when it is compressed.
> 
> MW of air (average) is 29, of water vapor 18, of CO
> 28, of CO2 44 . Draw
> your own conclusions !!
> 
> Greg
> 
>   So, mechanical compression ratio is
> >un-altered.
> >Another factor that EGR plays is as an agent that
> will
> >slow combustion.  This, in a sense, will benefit
> the
> >engine by having the same effect as a higher octane
> >fuel.
> >
> >For un-believers, disconnect your knock sensors and
> >drive the car.  It will rattle.  Now, disconnect
> the
> >EGR vacuum control source.  It will rattle
> EXTREMELY
> >bad.
> >
> >GG
> >
> >--- Mike <erazmus at iinet.net.au> wrote:
> >> Hi chaps,
> >>
> >> This issue re EGR recently, ie in last few mins,
> >>
> >> Any synopsis on considering using EGR as
> equivalent
> >> to
> >> compression ration control - I guess I mean 'well
> >> cooled'
> >> EGR through to not so well cooled and controlling
> >> the volume,
> >>
> >> The 'bar' of acceptable engine complexities seems
> to
> >> be rising,
> >> after all we know have VVL, variable length
> runners
> >> in current
> >> BMWs and VVT in many cars, led it seems mostly by
> >> the japanese
> >> in volume production...
> >>
> >> I read somewhere a technique for CR control was
> >> through moving
> >> the valves but it seems to me any sort of
> >> geometrical chamber
> >> issue re CR is frought with difficulties, so
> could
> >> some other
> >> issue such as EGR be in some way equivalent - ie
> >> Control
> >> volume *and* temperature for effective CR control
> ?
> >>
> >>
> >> Rgds
> >>
> >> mike
> >>
> >>
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