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

[Gerald Gnitter]

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.  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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