EGR?

[Gary Derian]

Exhaust is an inert gas as far as an engine is concerned.  EGR is used to
reduce peak combustion chamber temps which limits the formation of NOx.  In
the bad old days (1970's), EGR was added and ignition timing was retarded.
This combo made for badly running engines.  Of course back then, it was easy
to plug the vacuum line to the EGR, remove any impediments to vacuum
advance, and remove a spring from the mechanical advance.  Instant power,
smoothness and economy.

If the ignition timing is advanced when EGR is added, most if not all the
economy loss can be recovered.  Additionally, the engine now cruises at
lower vacuum which improves economy more.  Of course, without EGR, that same
engine could pull a taller gear which also reduces engine vacuum and
improves economy.

I would not use EGR in a hot rod unless you are using a fuel injected engine
which already has a good EGR setup.  In that case, removing the EGR and
recalibrating everything is a lot of work for little benefit (opinion here,
no data).  Although I did have an Eagle Talon with the turbo engine.  I
plugged the EGR valve and improved the economy from 23 to 25 mpg.  I tried
it in my wife's Volvo and only managed to set the check engine light.

Gary Derian <gderian at oh.verio.com>

Dave Sagers wrote:
> What is the purpose of an EGR and why is it used.  I'm trying to decide if
I
> should connect the EGR for my street hot rod.
>