Clay wrote:
--SNIP---
>if you want to talk temperature, they heat things up. What the EGR does,
>and does fairly well, is introduce residual gasses into the combustion
>process. What this effectively does is slow down the combustion process a
>bit,
--SNIP---
Exactly, carbon dioxide is not a combustible, as you know. Only a certain
amount of air and fuel can enter the cylinder before the intake valve
closes. Something like less than 10% of that is the recirculated
exhaust. That reduces the amount of new mixture which reduces the total
heat produced by the combustion.
The gas itself does not cool, as you say, but the affect of the gas in the
combustion process lowers the temperature of the burning atomized fuel.
>and this helps to prevent preignition becuase it is harder for the
>combustion process to start.
That is true. That is a side affect of the EGR operation. The sole
purpose of the EGR is to reduce the about of NOx that is produced.
>Combustion with the EGR is more complete
>though becuase of the raised temperatures in the combustion chamber, the
>particles have more potential energy to combust, and do so more readily.
In the time it takes for the EGR gas to get through the intake and to the
combustion chamber it has cooled dramatically. Yes it does warm the
mixture up, but not by much. Yes it helps atomize he fuel in the intake
runners on carbureted engines. Most of the heat produced comes from the
compression of the intake charge on the compression stroke, not by the EGR,
which is minimal, but yes it does a little. Feel free to shoot me an
email, I'd love to talk about this.
Mike
__________________________
mschwall@flash.net
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