Funny thing though - most of the newer engine designs do NOT have an EGR
anymore or it's a Linear PW Modulated EGR Valve which operates on
load/tp/vss/trans. Those don't even come close to the archaic EGR systems
of the 80's (and 90's). The reduced fuel economy and performance of the
70's and 80's vehicles is NOT due to the EGR system either - look at the
electronic carburetors, lean burn systems, and restrictive intake/exhaust
systems that caused so many issues as well. You can't narrow it down to
just one specific system.
Comparing Nascar and NHRA engines to factory emissions engines is like
comparing apples to tomatoes....sure they're the same type, but they're
entirely different applications and neither one can be swapped for their
intended purpose or use. How many times are NHRA engine torn down and how
many Nascar engines make it 100K miles or more? They don't use EGR or any
other type of major emissions system at all.
Now why do the engines run better when cold than hot? Simple - air
temperature, sensor input/output, and PCM calibrations. Take your IAT and
move it to the intake stream (from the hot intake manifold) and watch the
fuel and timing curve change (up to 4 degrees advanced timing and up to +5
on the fuel adaptives). Linear EGR system also work when the engine is
warming up. Open Loop operation is no more than 1-3 minutes from initial
start (year/model depending - sometimes sooner than that) which rules out
the cold/open-loop theory on the EGR anyway.
...and I have 2 Ferrets that agree with me. ;)
- Bernd
-----Original Message-----
From: rll [mailto:charger69rt@cox.net]
Sent: Tuesday, January 08, 2008 2:06 AM
To: dakota-truck@dakota-truck.net
Subject: DML: RE: EGR systems
>> How do hot exhaust gasses being rerouted back into the
>> combustion chamber "cool" the CC?? They have to be
>> hotter than the ambient air coming in thru the throttle body!!!
>
>
> I thought this was rather common knowledge. The air/fuel charge isn't
> "cooled", rather the *temperature of combustion* is reduced. The term
> "cooled" can be misleading as it is a relative term. We're talking
> something like 1500ish*F "cooled" down to something like maybe
> 1300-1400*F. Too "cool" results in incomplete combustion and HC
> emissions, while too "hot" results in high NOX. Does anyone know the
> exact Goldilocks range? I'm just going off my EGT gauge which is used
> simply to keep me from roasting a valve or piston.
>
>
Burnt or inert exhaust gases can be used for a couple of things.
The russians used it to fill the void spaces of aircraft fuel tanks to
give the benefits of a self sealing tank without the loss of volume
or extra weight.
The EGR uses the spent gases to spoil the quality of the mixture so it
burns at a lower temperature reducing the efficiency of the engine.
The reduced fuel economy and performance of the 1974 pigboats are
testament to the success of the EGR.
All this was done to reduce NOx...because it didn't look good...icky
brown cloud.
If there is some other horrible aspect of NOx i am waiting to be informed.
As mentioned, crap fed back into the mixture will affect combustion temps.
The implication that that the EGR is needed to control combustion temps
is inane. TOO HOT does not happen at correct mixture, it is usually a too
lean mixture. Running wide open throttle with a 12:1 mixture will be a lower
EGT number than at 16:1.
Under WOT if you go lean you burn down.
Some insight into EGTs in carting
http://www.foxvalleykart.com/egt.html
EGTs in aircraft..please excuse the massive link
http://209.85.173.104/search?q=cache:dBwmXGRFQfMJ:www.mangaero.org/leaning/
exhaust%2520gas%2520temperature%2520and%2520fuel%2520management.pdf
+exhaust+gas+temperature&hl=en&ct=clnk&cd=3&gl=us&client=firefox-a
I contend the EGR was a solution to a problem that never needed to be
solved.
The hi-po engines of the sixties didn't need it to keep from burning
down engines.
NASCAR or NHRA don't seem to use EGRs because guess what, they are not a
good
thing, they have one use, that is to reduce the efficiency of an
internal combustion engine
They were bogus in 1973, they were bogus in 1992 and they are a bogus
POS today.
To defend them is an insult to your own and my intelligence.
My 92 Dak gets about 1-2 mpg better when the EGR is blocked. Did you
ever notice
how your truck seems to run better before it is completely warmed up? I
know part
is the open loop before normal temps are reached, but the other is the
EGR is not on line yet.
my dakota will not pass the NOx standard with the EGR blocked, though
the HC and CO are almost zero.
And once again...what does NOx do...generates a brown cloud and makes
plants grow.
EGR, a politically correct solution to a problem that never existed.
Sorry, said it again.
Azie..thanks again for originally saying something about EGRs.
I remember reading and article in Machine Design in 1972 about the up coming
plan to use exhaust gas recirculation for smog control on the up coming
1973 model years. They explained how returning exhaust gas back to the
intake
would lower oxides of nitrogen.
I said at the time "what a stupid idea"...i was 25 at the time.
I say now in 2008..."what a stupid idea"...i'll be 61 on the 15th.
One difference, i have 4 ferrets that agree with me.
now lets go after CO2
rob/ferts/phx
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