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

[Greg Hermann]

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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