RE: EGR cools exhaust

From: Bernd D. Ratsch (bernd@dodgetrucks.org)
Date: Sat Jan 05 2008 - 11:16:12 EST


By introducing a small amount of exhaust gases back into the intake, you
essentially cool the combustion chamber by diluting the incoming A/F
mixture. There's plenty of other sites out there that explain how they work.
Believe what you may, but it does work and doesn't cause any reduction in
overall engine HP/TQ (unless they're not working properly).

The "old school" valve did have a lot of issue though - that's been fixed
since the introduction of Linear Pulse-Width modulated EGR systems.

On the intercooler, you're cooling the air charge which can be accomplished
in many different ways...not the same as an EGR system though.

- Bernd

-----Original Message-----
From: Azie L. Magnusson [mailto:maggie11@mchsi.com]
Sent: Saturday, January 05, 2008 10:00 AM
To: dakota-truck@dakota-truck.net
Subject: DML: EGR cools exhaust

Ray B. writes: >>Believe it or not, this time Bernd is correct. :-) Quote

from
www.about.com :
"The EGR valve helps your car more efficiently and completely burn fuel by
recirculating a portion of your exhaust and running it through the
combustion process again. This results in a cooler, more complete burn of
the fuel which decreases you car's noxious emissions by prohibiting the
formation of some harmful gases." There's more info there if you're
interested. <<

Oh!! Just because there is posted on the I 'net some
statement that says in effect that the EGR does cool the
exhaust, then that makes it a fact!!! Not hardly!!
Explain the process to a layman here, please.. I
understand how an intercooler on a turboed engine
cools the air prior to it entering the throttlebody or
carb or whatever, but the return plumbing from the
exhaust to the throttlebody/carb/intake doesn't go
thru any such device. It is plumbed directly into the
throttlebody/carb/intake from the exhaust.. Where
does it get "Cooled"???? There is nothing I see
that seperates the burnable exhaust from the spent
exhaust either, so in effect you are merely leaning
out the mixture in the combustion chamber which has
always meant Hotter combustion temps and is
subject to burning holes in pistons.. Now if you could
someway convince me that only the burnable gasses
were rerouted back to the intake, then that might
cool the combustion chamber because it would be
making the mixture(air/fuel ratio) richer, and the richer
the mixture, the cooler & therefore less likely to burn
pistons etc... I'm open to any and all tutoring here,
but you've got your work cut out for you if you intend
to convince me..

"One of the hardest things in life to learn is
which bridge to cross and which bridge to burn"

Azie



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