Thread: EGR

Originally Posted by AnD3rew

I have read a lot on here about EGR and blanking. But I haven't seen a comprehensive explanation of the issues in one place.

Can somone give me an EGR for dummies


What happens with them. And what to watch out for.

What versions and years have issues

Is the blanking something to consider doing prophylacticly?

What is involved with blanking.

While we're here, for those of us that bought second hand, how do you tell if it's been done already?

EGR = Exhaust Gas Recirculation

The main purpose of an EGR valve is to cut down emissions. It sits between the exhaust and inlet manifolds and when the engine is on over-run, it opens to allow exhaust gasses to be re-circulated through the combustion chambers.

Why?

It's so that any unburnt fuel can be burnt off recirculating... Cutting those emissions.

Thing is, after a while, the valve can get coated in soot and it stops working. If it stops in a closed position, you don't notice any difference but if it sticks in the open position, you are constantly drawing exhaust gas instead of air and you'll be constantly down on power.

So, blanking it off will not cause any problems mechanically... Though it could potentially cause problems with the authorities depending on your local regs...

HTH

M

Not quite. Egr is used to add exhaust gas with less oxygen to the combustion to reduce formation of nitrogen oxides which are a pollutant. The valve is open most of the time. Closed on full throttle.

Originally Posted by Dougal

Not quite. Egr is used to add exhaust gas with less oxygen to the combustion to reduce formation of nitrogen oxides which are a pollutant. The valve is open most of the time. Closed on full throttle.

Sorry Dougal - Mark is correct - the EGR only opens on trailing throttle. My Egrs are connected electrically but not to the exhaust and if I rig things up correctly I can see what happens with throttle response - closed all the time except when the throttle closes - on steady throttle, and increasing throttle the the EGRs are closed.

Garry

Originally Posted by Rohan

While we're here, for those of us that bought second hand, how do you tell if it's been done already?

You can't.....well not that I'm aware of. They don't really get dirty on the outside that easily so it sort of rules out the its cleaner looking than the rest of the engine bay technique! You can use a real time display on a scan tool and look at the operation to give you a good idea however. A brand new one will be perfect an older one not so perfect on the graph but it may not be bad enough to make a noticeable loss in power or to pull the EML on.
Not actually a very hard job to change them....just very fiddley....helps if you don't have huge hands, and a 1/4 drive uj with a bit of tape to hold it at an angle does wonders when you do the job.

If your buying a used car that's always been looked after by the same dealer it will be on the cars history of when they were last changed. Just ring up the dealer and get them to look it up for you

Originally Posted by fonfe

You can't.....well not that I'm aware of. They don't really get dirty on the outside that easily so it sort of rules out the its cleaner looking than the rest of the engine bay technique! You can use a real time display on a scan tool and look at the operation to give you a good idea however. A brand new one will be perfect an older one not so perfect on the graph but it may not be bad enough to make a noticeable loss in power or to pull the EML on.
Not actually a very hard job to change them....just very fiddley....helps if you don't have huge hands, and a 1/4 drive uj with a bit of tape to hold it at an angle does wonders when you do the job.

If your buying a used car that's always been looked after by the same dealer it will be on the cars history of when they were last changed. Just ring up the dealer and get them to look it up for you

Have a look at the link below, it is a line drawing of a TDV6 as if you were looking down on the top of it, the two pipes in yellow are removed if the EGR's are capped. In real life they are roughly 12 mm tubes from memory and are silverish in colour. It is easy to see if they have been removed or not if you take the engine cover off.

http://bellautoservices.co.uk/wp-con...V6-EGR-TOP.JPG

Yes Terry that is correct unless you have these simple blanking plates fitted:
Discovery 3 RRS EGR valve blank blanking kit 2.7 TDV6 | eBay
I have these type fitted as even with the plastic accoustic engine cover removed you cannot tell the EGR valves have been blanked. The pipes are reconnected but the butterfly vane is removed.
More detail here:
http://www.grahambethell.com/discovery3egrblanking.htm
However these instructions do not show the butterfly vane and it's removal.
These do:
http://bellautoservices.co.uk/wp-con...-MY06-TDV6.pdf

Originally Posted by garrycol

Sorry Dougal - Mark is correct - the EGR only opens on trailing throttle. My Egrs are connected electrically but not to the exhaust and if I rig things up correctly I can see what happens with throttle response - closed all the time except when the throttle closes - on steady throttle, and increasing throttle the the EGRs are closed.

Garry

No he's not. EGR isn't there for trailing throttle, it would produce absolutely no emissions improvement if that were the case.
It is not about burning unburnt fuel on overrun either.
You are aware that 100% EGR duty on many engines (like one of mine) means the valve is fully closed, not fully open?

What you are likely seeing with your setup is the valve closing at full throttle (as it does) and opening again afterwards.

EGR's sole purpose is to reduce the available oxygen in the cylinders at part load to reduce NOx emissions. NOx are formed at higher temperatures when excess oxygen is present.
EGR opens at idle and part throttle to allow exhaust gas (with lower oxygen content) to mix into the intake to reduce NOx formation during combustion. At higher loads EGR has to shut-off to allow the full charge of air for the best combustion.
EGR valves also have secondary functions with cold engine warmup and dumping excess boost to prevent turbo surge on rapid lift-off.

If you like I can post up the three EGR maps from my work car. These are EGR load switching (determine when to open/close the valves based on engine speed and load), EGR valve position (self explanatory) and EGR flow correction (MAF flow = engine airflow - EGR flow).