E . G. R Valve Explained.

[corkycat]

i thaught i would provide a thread clearly explaining what an egr is/ what it does/ how to improve it/ and how to maintain it.....

ive been tuning derv cars/vans and trucks for years now (mechanicaly)
and also petrol turbo,s i curently own and drive on of the hardest vw/audi engined cars to tune (apart from a remap)

lots of people have different views on the egr but heres the facts...

the egr valve was designed as a waste gas diveter on earier td engines to recirc the hot spent gasses from the plenum of the turbo via the wastegate the system proved a sucsess accidently and as greater emition controls have come into place these egr (exhaust gas recirculation) valves have become law within the car industries and it is now against the law to vent spent turbo gasses into the atmosphere... from the factory

the egr valve whilst conforming to eu regulations (a good thing) also cloggs up with oil emited from the turbo seals when the turbo gets hot and leaks oil (normal) thus resulting in loss of power and some cars smoke!

the egr on a derv works in exactly the same principal as a diverter valve on a petrol turbo (dump valve) FACT

the egr ITSELF is purelly mechanical in operation

the egr requires a ecu driven vacum system to function TO EU REGS!!

the egr can be modified to work more efficiently!!

when the egr is modified you will see near no turbo lag from set off (slow to pull out of junctions and slight hesitancy when accelerating is a result of most turbo lag) you will see more mpg more power smoother starting quieter running...!!!!

the egr works as follows.. when vacum is possitive (car running) the egr is shut completelly when you drive the vacum system fluctuates releasing boost at variable levels through out the rev range sometimes only opening the valve by 1mm thus resulting in loss of boost untill the turbo spools again (you wouldnt even be able to feel the system doing this)

the sooting up of the egr is normal and you should be removing your egr every 20k to clean it and reinstall... egr vaves fail when the cleaning process is not done so the vacum creates resistance against the diaphram within the egr itself thus breaking the seal in the diaphram..

egr valves are not all the same- some you can bypass some you cant some cars run better bypassed some dont some cars you can buy an upgrade for some you cant..

blocking off the egr vacum pipe (rubber pipe going to the egr) does the car no good and although you will not show a management light (if you do you have a prob elswhere showed up by blocking this pipe off!!) all you are doing here is asking the turbo to work harder as there is no resistance on the diaphram resulting in boost leak..

removing the egr completelly is an option but you wont see gains in all aplications although in some engines you will see clean burn

there are the basics i will edit as and when i dont wish for people to use this thread as a slagging or arguing thread its here to purelly give the FACTUAL information on the egr
i will be posting another thread soon showing the mods you can do to make your egr work more eficiently but i am currently waiting on my car returning from a gearbox rebuild so please bear with me.. any questions please ask...
ps please bear with my spelling as i work with spanners and not a dictionary!!

[Col]

A few questions ?

A Diesel does not have a throttle and therefore does not need to 'dump' its boost to atmosphere. So how can a petrol diverter valve be compared to a diesel egr valve?

My understanding is that the egr valve is simply a device where by exhaust gases are partially mixed back into the inlet tract to be re-burnt. I do not see or understand how there can be any postives on havingone fitted to a car other than in the reduced emissions of NOX ?

I don't understand how an EGR can add to performance or drivability at all, surely it would be the opposite by introducing air with less oxygen back into the combustion process reduces performace and power?

I am more than interested to learn to the contrary ?

[corkycat]

an egr valve is exactly the same as a petrol diverter valve they both have a diaphram that lifts the same pistin inside to return gasses into the inlet manifold or in some cars into the exhaust manifold.
turbos work in exactly the same way petrol or derv the reason the egr on a derv is made of metal and not plastic like petrol cars and also not tracked into the rubber piping is the gasses are a lot hotter..

if you plug a laptop into your car and do live tracking on the egr you will see that when you press the throttle the egr is shut thus everything holding boost in all pipes ect ect... when you take your foot back of or when changing gear you will see the valve open and release the boost (exhaust gasses) from the boost pipes and recirc it into the inlet.

try this on a petrol turbo car also and you will see exactly the same peramiters.. hence why its called an exhaust gas recirculation valve.

you can fool the system into thinking there is a partial leak while still holding settings in the boost pressure sensors thus the turbo clamping for longer and holding more boost.

if you are still unsure remove your air filter lid and the filter, get somebody to sit in your car while you are under the bonnet and get them to rev the car hard and let off... you will hear the egr,s operation wich sounds the same as an atmospheric dump valve on a petrol turbo car!

some people fit aftermarket dumpvalves to dervs and this tracks into the piping to the egr.. (i do not recomend fitting of an atmospheric dv on a derv)

if you are still unsure and are somewhere near the lakes i can show you my car and the mods i have done

[snapdragon]

Codswallop! of the highest order! An EGR valve is a way of introducing controlled amounts of cooled exhaust gases into the intake during light loads in order to reduce NOX emissions. Any inert gas will work and exhaust gas is suitably 'inert' for this purpose and is readily available. It reduces NOX emissions by reducing combustion temperature by a few degrees such that Nitrogen no longer reacts with the Oxygen.
The ECU will request the exhaust gas and look for a corresponding drop in metered air from the airflow meter to confirm the quantity of exhaust gas. If no MAF drop is sensed, the signal for EGR will increase until a fault code is set.
It has nothing to do with turbos.
Read a book or look on wikipedia for more info.

[corkycat]

along the same principal only the way i have explained it is in the way someboody can understand that does not understand the tecnical side.
as i stated in the first post i dont wish to argue as everybody is entitled to an opinion.. ive been doing things this way for years and with very good results (modification wise) and lots of pleased people..
plenty of members on here have already done my mods and send thier regards on the tips so hardly codwallop!!

[Col]

What mods are they?

[corkycat]

photos of mods i have done will be posted as soon as my camera is sorted.. they consist of boost sensor pipework relocation egr modificatoin pump timing advanced by 3 degrees matched to the tuning box i am running. along with others

[Ben]

a very good and informative thread - moved from passat section. A benefit to all members.

[corkycat]

It has nothing to do with turbos.

then why does the stainless pipe run from the egr to the wastegate on the turbo??
why does the egr release boost pressure when the wastegate opens on the turbo??
not wanting to argue but i think you are misunderstanding the principal of the egr valve (EXHAUST GAS RECIRCULATION) going back to my original post the reason it is there and not venting to atmosphere is to keep within EU RULES.
if the egr was there to reduce nox emissions then why is there no sensor on the egr itself?
wikipedia? who is she?

[zollaf]

what about egr valves on a naturally aspirated diesel engine?