I understand the theory of the ERG valve. It's to recycle some unburned
hydrocarbons back in to the engine cylinders. In practice, it covers the
intake manifold with an oily goo, clogs the fuel injectors and spark
plugs, and builds up deposits on the valves, decreasing the car's MPGs.
My link from the exhaust to the ERG value broke and while I was waiting
for Ford to get replacement parts, my MPG increased by 4 MPGs.
What's the point of keeping this failed idea?
The EGR valve is used to reduce combustion chamber temperatures. High
combustion chamber temps can produce oxides of nitrogen..... this is the
component of smag that reacts with sunlight and turns into a brown haze -
and it's not good for your lungs. While the thought that increasing fuel
consumption may be bad for the environment may seem reasonable, it is our
tailpipe emissions that are the concern.
I need to add that the EGR flow is also used to eliminate engine "ping"
during acceleration. This allows timing to remain advanced (producing better
power) while reducing the chance of damaging preignition.
It's not that the idea is either a bad one or a failed one.... it is that
increased fuel consumption is a byproduct of reducing emissions.
Thanks for the input. The ERG valve was created before fuel injection.
Carb days. With modern day fuel injection systems, wouldn't it be better
to have a clean intake system and let the fuel injection chip control
the chamber temperature? I'm not looking to be a smart ass, but I don't
see how burning more gas is better? Also, how can reducing the
efficiency of a chamber is better?
Much of the US tax policy on autos, is based on MPG. If maximizing MPGs
is producing more oxides of nitrogen, is this bad US policy?
Basically, it just the way the chemistry works. Spent exhaust gasses are
used to dilute the intake charge while anything they can do with the
injectors can only make the mixture rich or lean (adding the inert exhaiust
gasses results in no change to the air fuel ratio). Your extra mileage was
experienced because less "pedal" was required for the same results... but
the expense was the higher combustion temps that cause a major component of
On older vehicles, EGR timing and function was neanderthal by todays
standards and was the cause of rough idle, poor throttle response and any
other number of driveability concerns. EGR systems are not a perfect
cure.... with current technology, it is the only viable cure we have. The
engineers could limit timing advance to reduce chamber temps but the
power/mileage hit would be greater than what we see using EGR. Fattening up
the mixture would also be counter-productive and increase HCs as well as
costing even more gas than the EGR.
Not a cure nor a panacea, the EGR system is simply the lesser of all the
Again, just looking for information, if you dilute the amount of
air/fuel going in to the chamber, you would need more RPMs to get the
same HP than a chamber without dilution.
Do you have a source that I could review that showed lowered combustion
temps create less pollution?.
I used to build racing motorcycle engines, and found that the better
gasses flowed in the intake and exhaust systems, the better the power
and efficiency of the engine was.
My 2 cents:
I was told once to think of the EGR function in a modern vehicle as a way to
reduce engine displacement while cruising, when power is not needed. Since
exhaust is essentially inert, it takes up space in the cylinder without
changing the air/fuel ratio...
I can't argue this point much one way or the other but in my car (which has
a problem clogging the EGR lines every once in a while) I don't see much
fuel economy difference either way. Maybe it pings a little easier when
You doubt my veracity and then you want me to do your friggin' homework....
Googling "EGR valve" yields about 149,000 hits. The three I am including are
pretty good about explaining it. It has nothing to do with combustion
efficiency and nothing to do with power produced... it has everything to do
with the air that we breathe. If you don't feel that the device fulfills
it's design intensions or if you feel that the brown shit hanging in Los
Angeles Basin has nothing to do with cars, why on earth would manufacturers
be installing these devices on cars and why on earth would the EPA be
demanding reduced emissions?
As Paul points out... why would we want to produce more horsepower than we
require for the task at hand?
Go to smog testing station.
Stick sensor up tailpipe.
Disconnect EGR (not ERG) valve.
Reconnect EGR valve.
Oxygen bonds with Nitrogen under high temps (around 2000 F) to make NOx.
Keep the overall combustion temp below that, much less NOx produced.
How, by adjusting the amount of gas mixing with the available air?
There is an "ideal" (stochiometric) mixture where all the gas and air are burned.
Too much = unburned gas out the tailpipe, catalytic converter meltdown.
Too little = lean misfires (gas out the tailpipe), and high temps (NOx).
The "tree huggers" loved the old VWs too, due to their great gas mileage,
which they assumed meant it was a very efficient engine. Unfortunately,
they didn't notice that they were spewing 100+ times more crap into the
air than today's cars.
I'm still waiting for someone to explain why we need to waste billions
of gallons of gas to pretend that the ERG value saves the earth. After
all, using gas causes global warming.
I forgot, It's just politics. And greed
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