This is an in-depth video about the EGR or Exhaust
Gas Recirculation system. We will cover the history and evolution of these devices, their operating
principle, their differences in petrol/gasoline and diesel engines, their benefits, their drawbacks,
real world problems and much more By the end of this video you'll have a firm grasp of this
very important but also often very misunderstood engine component and you'll be able to make
an educated decision yourself about whether it should be deleted from your engine or not. So,
instead of feeding you subjective, overgeneralized opinions and telling you what to do, today
I'd like to empower you with knowledge so that you can make the decision yourself and I would
appreciate it, that after watching the video you tell me what kind of conclusion you have
reached. So, let's get started and let's start with the history. Why were EGR devices invented
and placed on engines in the first place? As you probably know the reason is emissions. But it's
very important to understand specifically what kind of emissions are EGR devices concerned with,
and they are concerned with NOx or nitrogen oxide emissions Now, nitrogen oxides form whenever we
have sufficient heat in the presence of nitrogen and oxygen. as you know, Earth's atmosphere, in which
we live and the air which we breathe is composed largely of nitrogen and oxygen which means
that all we really need is heat. So what do you think is one of the largest sources of nitrogen oxide
emissions? Well, believe it or not, it's lightning storms The temperature of a single lightning bolt is around 28,000 degrees Celsius or around 50,000 deg Fahrenheit That is an insane amount of
heat and it creates a lot of nitrogen oxides But the catch is that lightning storms occur high
up in the sky, somewhere around 4 to 5 km above Earth's surface and most lightning bolts,
they don't really strike the ground. Instead, they are between two clouds or within a single
cloud. And, as we know, lightning storms they never occur continuously in the same place, and they're temporary. They occur at different places at different times Unfortunately, in contrast to
this traffic occurs continuously in urban areas where most humans live and traffic also occurs
on the surface level where humans also live So traffic, which has combustion engines mostly, which
create a lot of heat whenever they are operational is actually the main source of nitrogen oxide
emissions within the localized area where humans live Which means that it impacts negatively human
health unlike thunderstorms and lightning storms which occur high up in the sky. Now, nitrogen
oxides are bad for the environment because they react with other elements and form smog and acid
rains. But unfortunately their impact isn't limited to the environment because nitrogen oxides are
composed, mostly, of nitric oxide, NO, and nitrogen dioxide, NO2. Of these two the dioxides are the ones
which are bad for human health because they lead to all sorts of respiratory health issues and
diseases, such as asthma, lung disease and so on and so forth The problem is that the more heat
and the more pressure we have the higher the ratio of dioxides within the nitrogen oxide emissions
that we create. And interestingly enough this means that one of the first major widespread sources
of increased nitrogen dioxide emissions from vehicles were actually early catalytic
converters, two-way catalytic converters A device primarily designed to reduce emissions increased
nitrogen dioxide emissions. This occurred because back in the 70s when they were introduced most
vehicles ran carburetors and carburetors are simply not as accurate as electronic fuel
injection, and in general they tend to run richer or with more excess fuel in the combustion
chamber. And this means that, because we have more excess fuel, more unburned fuel or unburned
hydrocarbons are reaching the catalytic converter and that's exactly what a catalytic converter
is designed to do. It is designed to do two things A two-way catalytic converter does two things.
And that is to burn unburned hydrocarbons and to convert harmful carbon monoxide into less
harmful carbon dioxide. Because we have more unburned fuel reaching the converter it leads to a
higher chemical reaction rate and increased heat Some would even glow red hot that's how
hot they became. And this increased heat meant that the catalytic converter itself became a source of
increased nitrogen dioxide emissions Fortunately, manufacturers quickly resolved this and we moved
on to three-way catalytic converters This fact that more pressure and more heat leads to more
dioxide emissions tells us that the fundamental issue here is the technological advancement of
engines themselves, because for the past 100 years of internal combustion engine development that's pretty much what we've been doing. Increasing heat and pressure Let's observe diesel engines
as a good example. Early naturally aspirated diesel engines had 95% nitric oxides and only 5%
nitrogen dioxides in their emissions But in our pursuit of more performance and more efficiency we
increase their compression ratios and then added turbocharging which is heat and pressure. And so we
not only increased the overall amount of nitrogen oxide emissions but we also increased the ratio
of nitrogen dioxides. So more modern Diesel engines have somewhere between 15 to 70% dioxides within
their nitrogen oxide emissions. In other words our our constant desire for more performance and more
efficiency has led to more heat and more pressure But at the same time, we want to be healthy and
live in a non-toxic environment so we're also trying to reduce emissions from engines
while we're also increasing their heat and pressure And the problem is that this increase
in power and efficiency is diametrically opposed to a reduction in emissions, it's like asking an
athlete to achieve ever greater results while at the same time continuously reducing their
training time. Achieving such a feat requires great creativity and the EGR or exhaust gas
recirculation system is one such feat of creativity because, on paper at least, it aims to
reduce emissions without sacrificing performance and efficiency So, as the name implies Exhaust Gas
Recirculation means that we take exhaust gas which comes out of the combustion chamber past the exhaust
valves and exhaust manifold. We take some of that and we bring it back into the combustion
chamber. The question is why would we take that which naturally comes out - back in. EGR
deletion proponents, they love to say that EGR is like eating your own excrement, and although it
sounds disgusting technically it is. But the thing here is that nature is far more advanced than
anything man-made and things actually have use for human excrement. It's biodegradable and
there's bugs and bacteria that degrade it and it can even help plants grow, well at least the
kind of excrement that isn't based on a diet of Taco Bell and Twinkies can help plants grow.
But anyway, when it comes to the excrement of engines, once it gets past the turbocharger,
nothing really has any use for it. It's harmful to life so we take some of it and we put it back
in and this means that we are simply reducing the amount of emissions that reaches the atmosphere.
But this is not the main goal of the EGR system to just reduce the volume of exhaust gas coming
out. The main goal is to reduce heat inside the combustion chamber, and by reducing heat we reduce
the amount of nitrogen oxides produced We reduce heat because exhaust gas doesn't really contain
much oxygen in it, very very little, and this means that exhaust gas doesn't have what it takes to
burn again. That makes it an inert gas. Which means that it acts as a buffer. We take the exhaust gas,
and it fills some of the internal displacement, internal volume of the engine which means that
once we do that there is less space for oxygen to occupy inside the engine. Because there's
less oxygen we have to add less fuel to maintain an optimal air fuel ratio. Less fuel, less oxygen - a
smaller weaker combustion - less heat Therefore, less nitrogen oxides. Also, reducing the amount of
oxygen means that the nitrogen doesn't have enough material to react with, to form nitrogen
oxides. An alternative way of looking at EGR is to call it a temporary displacement reduction
device that relies on gases. Because if we fill some of the displacement of the engine with an
inert gas the engine effectively becomes a smaller engine and a smaller engine creates less emissions
and also it requires less fuel and yes it makes less power But the important thing to understand
here is that the EGR system works in conjunction with engine load. It is not active all the time.
Early systems were vacuum-actuated. When throttle openings are small engine vacuum is high. One side
of the little EGR valve was exposed to this vacuum while the other side is exposed to exhaust gases
which means that we have low pressure on one side and high pressure on the other side. This pressure
difference causes the valve to get opened and allow exhaust gases to run past it and go back
into the combustion chamber via the intake tract More modern systems are more advanced and they
are controlled by the engine control unit or ECU, which controls the exact position of the EGR
valve or flap or whatever based on, for example throttle position, coolant temperature and any
other desired parameters. Also more modern more advanced, more complex systems have an exhaust
cooling section which runs coolant through this section to greatly reduce the temperature
of the exhaust gases coming back into the combustion chamber which helps to to reduce
combustion temperatures even further All of this tells us that the system cannot impact peak
power output because the moment when you floor it You don't even have to floor it, anything usually
above 70, 75% throttle fully closes the EGR valve because it is assumed that at high throttle
openings you are demanding high performance and high power output from the engine. So, no
exhaust gas is allowed into the cylinder and all of the cylinder volume gets filled with oxygen and
fuel for maximum combustion pressure acting on the piston generating maximum torque and maximum
power output. Therefore, the EGR system does not impact peak power output. It only reduces power
at small throttle openings, otherwise known as cruising conditions. But this is a scenario when
you're not demanding performance from the engine anyway so reducing power here is inconsequential.
EGR systems also improve efficiency with petrol engines because they reduce pumping losses. Pumping
losses are highest at low throttle openings because this is when the engine is trying to
breathe through a small orifice. iImagine trying to breathe through a straw. It's pretty hard and the
engine wastes energy overcoming this breathing obstruction Now, the EGR is as we said a temporary
displacement reduction device. Which means that to achieve an equivalent amount of oxygen
and fuel inside a cylinder we have to open the throttle more. In other words, we're opening the
throttle more for the same performance and higher throttle openings mean reduced pumping losses and
thus improved efficiency. Unfortunately things are not so great with diesels and EGRs where we have
a sort of a catch 22 and that's because a diesel engine naturally does not need a throttle valve
because in a diesel when we operate the throttle pedal with our foot we are actually directly
controlling the amount of fuel being injected into the engine. In other words we are allowing all
the air that can get into the engine to get into the engine at all times. In a petrol engine when
we operate the throttle pedal we are directly controlling the amount of air coming the into the
engine. We are allowing more or less air into the engine, the ECU measures this and then injects
a corresponding amount of fuel to maintain an optimal air - fuel ratio for the desired conditions.
And this means that in a diesel, because we don't have a throttle plate, we have
atmospheric pressure inside the intake manifold at all times If we have atmospheric pressure
at all times it means that we don't have engine vacuum needed to open the EGR valve, because we
need a pressure difference to open the valve So what we do in a diesel is that we introduce a
sort of butterfly valve similar to the throttle of a gasoline engine in order to operate the EGR
valve which means that we are introducing pumping losses to the diesel, which it naturally didn't
have, so that we can reduce emissions Which means that we are reducing them at the expense of engine efficiency. On top of this a diesel engine needs more heat and more pressure to achieve the most
complete and most optimal combustion compared to a petrol engine, which means that naturally
diesel engine produces more nitrogen oxide emissions. When we add an EGR system to a diesel
engine we reduce the heat inside the engine which means that we achieve less than optimal combustion.
When combustion quality is reduced in a diesel the exhaust stream of the diesel is going to contain
more soot and then the EGR is going to recirculate that soot back into the engine through the intake
manifold which can increase carbon deposits in the engine, and this then can lead to reduced
performance and even hypothetically increased engine wear. Which means that overall in a diesel
the reduction in emissions seems to come with a pretty high price. Well yes, and no. Because what I
just said about diesels and EGRs is only partially true So issue number one: Adding an EGR to a
diesel engine reduces efficiency because it forces us to introduce a butterfly valve in the intake
manifold so that we could create a vacuum so that we could create a pressure difference to
open the EGR valve. This is only true for older diesel engines, let's say late 90s, early 2000s.
After that, usually most diesel engines with an EGR have an electronically controlled EGR, controlled
by the ECU so we don't need to create a vacuum in the intake manifold which means that we do not
need to have a butterfly valve on a diesel engine. However pretty much
all diesel engines nowadays do have a butterfly valve in the intake manifold. However
it is open the entire time which means that it doesn't create any sort of significant pumping
losses as the engine is running and it only does some action, closes when you shut down the engine so that it makes the engine shut down smoother and quicker basically Issue number two: the EGR
system causes carbon deposits inside the engine because it recirculates the soot present in the
the exhaust stream of diesel engines Again, only partially true, because there is a fundamental
underlying issue behind carbon deposits in all engines and it's not the EGR. It's something
called the PCV and PCV stands for positive crankcase ventilation. It is a system that relieves
the crankcase of excess pressure. Why do we have excess pressure in the crankcase? Well that's
because piston rings cannot create a perfect seal They do an amazing job for most of the
life cycle of the engine but as the engine ages they are less and less capable of creating a good
seal so combustion gases escape past the piston rings and they are pressurized and they get into
the crank case. So as the engine is running the crank case pressure builds more and more and if we
didn't relieve the crankcase off this pressure we would have oil seals blowing up or your oil
dipstick being sent flying out of the engine So what we do is that we relieve the crankcase of this excess pressure and most engines do this by relying either on vacuum present in
the intake manold or vacuum present in front of the turbocharger to help these gases escape back into the engine. Now the problem with this is that the crank case is, as you know, full of oil
which is slushing around and there's oil vapors and oil mist. So these gases, they carry oil. Sticky
oil Vapors back into the engine. Now most engines they do have some sort of oil and water separator
which is meant to get some of these oil vapors back into the crankcase, get actual oil back into
the crankcase, and let the pressure escape but none of them are, of course, perfectly efficient. So
inevitably some oil vapors get inside the engine and they are sticky. This means that the soot that
comes back into the engine has something to stick to In fact, if we didn't have the PCV system
then the soot wouldn't really stick to anything because the soot in the exhaust stream itself is pretty dry. The soot isn't good at sticking to anything and it would probably just
go through the engine without being layered and deposited onto everything in such an amount if the
PCV system wasn't there to give you oil vapors as a good sticking surface. And in fact if you look
at the pictures of clogged diesel parts, you can see that in most cases these deposits are kind
of, they seem oily, they seem kind of shiny they seem wet. And this tells you that it's not the soot
alone because it's a mixture of soot and oil and this is just great at sticking to stuff so now
you must be wondering, "Okay, can I delete the PCV system?" Well, no you can't, but what you can do
to help alleviate and potentially reduce these problems and extend the inter intervals between
required cleanings of engine internals where the deposits are, is to install an oil catch can. This is a system, a little can, which is relatively inexpensive, relatively easy to install and you
install it somewhere in the PCV system between the crank case and the intake manifold or turbo
entry and this has a baffle, internal baffle system It catches some of the oil. The downside
is that you have to keep an eye on the level of the deposits in the oil catch can and you have to
empty it from time to time and this has to be done properly not poured into the sewage drain in front
of your house, because this is a toxic residue So you have to keep an eye on it, you have to empty
it often. And different catch cans are efficient to different degrees but none of them are capable
of perfectly 100% eliminating oil vapors from the inside of your engine. There will still be some. You
are just trying to reduce the problem. However an oil catch cannot hurt anything, so you know, not
a bad idea. So the EGR system in diesel engines it is certainly not an ideal solution but it's not
that bad. It does not impact engine efficiency in a noticeable way and it is not the primary culprit
behind the carbon deposit inside the engine So we have to ask ourselves where does all the hate for the EGR and all this push for deleting it come from? So many people saying it,
that you got to delete it. "It's the first mod you got to do" and so on and so forth. To understand
this phenomenon, why this device is so despised there are actually four main culprits. And it's
governments, it's manufacturers, it's the users and it's the tuning shops, EGR deletion service
shops and EGR delete kit manufacturers So yes, I'm basically basically blaming all the stakeholders,
but bear with me it's going to make sense When the EGR, when nitrous oxide... um nitrogen
oxides emissions were first observed and their negative effects measured
with scientific research, governments mandated to manufacturers to reduce nitrogen oxide
emissions, and they mandated this through laws and legislation which contains basically nothing
more than telling manufacturers this is how much nitrogen oxide emissions your new vehicle can have
and that's it. It's basically just a number and it doesn't include anything about the reliability of
the system, the ease of servicing of the system the redundancy, the whatever. Just a number.
Faced with such legislation the manufacturers of course scrambled to create a quick solution and
of course manufacturers being manufacturers they chose the cheapest solution which also included
zero user effort needed for it to function So manufacturers decided to go with EGR and
they scrambled, they made the first generation of these systems, they were kind of botched up
and the result is that they were garbage Most of these early EGR systems, they failed pretty
frequently, they clogged up far too soon and they created very much increased servicing costs
and increased downtime for owners of these diesel vehicles and it is objectively hard to blame these
people for wanting to delete these systems because they simply were pretty bad and most of the bad
rep of EGR systems comes from this early period Since then, these systems have come a long way and
they are much better and they usually don't really cause any issues for the first owner and during
the warranty period. Most of the issues appear as the vehicle ages and they appear for owner 2, 3, 4,
whatever, because the higher the mileage the greater the amount of oil vapors. Because the
poorer the ring seal the greater the amount of oil vapors the more everything gets clogged. And not
just get clogged, it gets clogged more often and here this brings us to the users. A lot of people
buying a used car will choose a high mileage car because a higher mileage car is cheaper and this
then allows them to get into a more upmarket more luxurious, better-looking model if
they go for a higher mileage. Which means that a a certain number of people choose a vehicle that
they can afford to buy but not that they can afford to
maintain. Often diesel seems like a good choice because of all the fuel savings but unfortunately
choosing these vehicles. Complex turbo diesels with high mileages so that you can get into a fancy
car results in all the fuel savings being either offset or far outweighed by the increased
servicing costs. And then faced with these increased servicing costs users choose to somehow
try and cut their losses and logic tells them because, of course, not everybody knows everything
about engines and cars, so logic tells them that if they delete that which causes these
increased servicing cost, if it isn't there then it can't be serviced and more money
stays in the pocket. And this is often further made worse by the fact that to cut losses and to,
you know, safe finances people choose the cheapest fuel and cheapest engine oil to maintain cars and
this further accelerates carbon deposits and so they say "let's just delete it" so I can keep more
money and there's often zero concern for the air that we all breathe and this then leads us to the situation that it leads us to with many people deleting these systems Again governments and manufacturers
they take a chunk of the blame here because pretty much all the problems that appeared with
EGRs can be solved with a simple manual cleaning You remove it, the EGR, you clean it, you put it
back in. You don't even need to replace anything important There isn't much cost in this. You put it
back in and everything is restored. Performance, NOx emissions, everything works properly. However
some manufacturers locate their EGR in such a place in the engine bay that getting to it
requires taking apart half of the engine bay and this then leads to very high servicing costs.
Although there is no parts being replaced Again, here's the blame because the legislation should
have said this device must be made easy to service because if it were accessible then its
servicing cost would be reduced and owners would not be prompted to delete it as much. And the final
piece of the puzzle is the tuning shops that delete EGRs and manufacturers of EGR delete
kits, and these can in some cases be the same business They're a major culprit as
well because they realistically know in what kind of position the owners are and so they tell them
what they want to hear. "Welcome to a video on why EGR valves are the devil EGR valves were invented
for one or two purposes, um one of which and pretty much the only one I know is emissions which you
shouldn't care about." They offer overgeneralized statements and they promise that they will increase
the power output, that they will reduce servicing costs, that they will increase engine life simply
by deleting the EGR system. In reality this is is not true. The sole removal. just the deletion of the EGR system can not increase power. The power increase comes
from the subsequent necessary reprogramming and re-calibration of the engine. The only place where
the EGR system, the only kind of vehicle where the EGR system can just be deleted by getting a
block off plate, blocking it off and doing nothing else, is in very old engines where
this system is purely mechanical. But these cars nowadays, I don't know, there's not many of them.
Most people that delete EGRs, they have more modern vehicles and when you remove an EGR from these
engines you cannot simply just remove it because the engine is designed, the programming of the ECU
of the engine is designed to work in conjunction with the EGR. When you remove the EGR you have to
lie to the system that the EGR is still there and then you have to reprogram the fueling, the fuel
timing and the fuel quantities because things are now different. There is now a different amount
of oxygen in the chamber and not just that, most EGR deletion shops, what
they do when they do the reprogramming, it's very easy they can mess about with fuel
timing, fuel quantity, boost levels to increase peak power a bit and then they can present this
increase of peak power and say "ah this happened because I removed the EGR". Removing the EGR will not
increase peak power. What may restore your power is simply because when when the EGR is removed the
stuff is cleaned, so it was not working properly in the first place. If you remove a properly
working EGR from an engine you will not increase power. This is achieved by the subsequent
reprogramming, recalibration of the system which must be done because you have removed the EGR.
And finally there's also the claim that the EGR system reduces engine life because it increases
engine wear, because it introduces soot and soot is and an abrasive so it leads to increased wear
between all of these sliding and rotating surfaces inside the engine. To me this really doesn't
make sense because the largest soot particles have a diameter of 10 microns. The smallest engine
clearances are almost never smaller than 30 microns and most oil filters don't really filter
out anything smaller than 30 microns, because it can't hurt the engine, because it's smaller than
the clearance, and so it just passes through But even if you don't believe my micron talk, it is clearly evident that the introduction of EGR has not contributed to some massive average
reduction in engine life because, good properly designed and properly maintained diesel engines
they still do hundreds of thousands of miles easily and nowadays most engines aren't scrapped
because they wore out they're simply scrapped because it is financially, doesn't make sense to keep
maintaining them or they're designed not to be rebuilt So it's a pretty complex topic. There
you have it, the the key facts about it and now I'd really like to hear your opinion. Your
conclusion when it comes to all of this As always thanks all for watching I'll be seeing
you soon with more fun and useful stuff on the D4A channel
