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

[Greg Hermann]

At 12:12 PM 12/16/02, Gerald Gnitter wrote:
>I suppose you have taken the density of the gas into
>consideration in your forumula?

No. was comparing work required to compress equal masses or mass flows of
gas, not equal volumes.

Greg

>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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