[bobda]

Have there been any instances or is there any thought regarding blanking the EGR valve off leading to turbo failure or increased wear on the turbo?

I ask because I had a turbo in a Renault DCi engine fail a few years ago due to a faulty EGR valve (in those engines they stick closed - same conditions as blanking). The theory goes that by introducing exhaust gases to the inlet it cools the combustion chamber and leads to lower exhaust gas temperatures. There's plenty of chat about it on forums if you Google 'EGR turbo failure'.
My failure occurred at high speed under continued load in top gear (make of that what you will) and resulted in the turbo ingesting most of the engine oil and spewing it out of the hot exhaust - obviously resulting in a lot of smoke. I was lucky that it didn't use all the engine oil and lunch the engine at the same time. I had the turbo fixed under warranty and sold the car.

 

[bear1]

strange.... The EGR only works at low revs (in the city or traffic) so once you start speeding up the egr isnt working anymore. There must have been other problems if the turbo failed and im assuming with low mileage considering it still had a warranty. I know that the EGR can cause problems over a long-term basis to the turbo but.... I would also imagine that making such a modification to the car would void the warranty.

 

[t3yls]

guess it reduces the manifold gunking up.

Switching it off -lesser of two evils maybe?

 

[bobda]

strange.... The EGR only works at low revs (in the city or traffic) so once you start speeding up the egr isnt working anymore. There must have been other problems if the turbo failed and im assuming with low mileage considering it still had a warranty. I know that the EGR can cause problems over a long-term basis to the turbo but.... I would also imagine that making such a modification to the car would void the warranty.

Not particularly low mileage - it was around 60k and it was a 52 plate car, the failure occurred in early in 2006. The warranty was because I bought it from a dealer around 6 months earlier.

I thought the EGR was linked to boost pressure rather than RPM? More speed doesn't necessarily mean more revs though - 50mph in 6th gear = 1.5kRPM. Unless the ECU takes into account road speed in the EGR operation?

guess it reduces the manifold gunking up.

Switching it off -lesser of two evils maybe?

Blanking does in theory reduce the gunking up as it would just be air (and oil breather return) going back into the inlet rather than potentially exhaust gases as well. But having the EGR disabled in software via remap etc has the same effect as blanking, albeit without the check engine light being triggered.

 

[bear1]

ah ok didnt realise it was a 9 year old car. I dont think for instance at 60mph the egr is working, the egr will only give you a better take off and then after that it doesnt really do much for performace... i may be completely wrong though so take it with some salt. I wont blank the egr in my jtd cause its there for a reason.

 

[bobda]

ah ok didnt realise it was a 9 year old car.

It was a 4 year old car at the time of failure.

I dont think for instance at 60mph the egr is working, the egr will only give you a better take off and then after that it doesnt really do much for performace...

EGR doesn't give any boost to performance.

i may be completely wrong though so take it with some salt. I wont blank the egr in my jtd cause its there for a reason.

An EGR valve is there for emissions. Read this if you want to learn a bit more; Exhaust gas recirculation - Wikipedia, the free encyclopedia

 

[hdseven]

biggest cuase of turbo failure is bad oil or blocked oilways, oil starvation will kill a turbo in no time at all

and as said egr is exhaust gas recirculation nothing to do with how the turbo works, just a trick to kep emitions cleaner

Gary

 

[bear1]

sorry, didnt see the 2006 bit.
Blanking the EGR does give a boost to performance but only low down performance i.e. low down in the revs.

 

[hdseven]

sorry, didnt see the 2006 bit.
Blanking the EGR does give a boost to performance but only low down performance i.e. low down in the revs.

how does it boost performance?
itll only change performance if the egr was stuck, the system is there purely to lower the nitros oxides to make cleaner running cars

anyway i cant see how it could damage a turbo...........but i will ask one of out tech guys if its possible

Gary

 

[t3yls]

mine is blanked off with a plate. Runs better than ever. Was constantly cleaning that valve as i refused to buy another new one. Now got used to the little greeting light when I start her up.

My performance has improved cus that crappy valve was slowing it down lol.

 

[vetch]

Sorry to go off topic, but how easy is it to blank off? As in time and cost?

 

[bobda]

biggest cuase of turbo failure is bad oil or blocked oilways, oil starvation will kill a turbo in no time at all
and as said egr is exhaust gas recirculation nothing to do with how the turbo works, just a trick to kep emitions cleaner

In normal operation it shouldn't affect the turbo too much. But since turbos are driven by exhaust gases, it does have a bearing on how the turbo operates.

Basically - exhaust gases leave the engine via the exhaust manifold and through one section of the turbo which spins a turbine linked via a shaft to the other section which forces air (via the intercooler) into the engine.
The EGR valve is connected by a branch off the exhaust manifold before the turbo and under low boost levels (<30% or thereabouts I believe) it is open which means exhaust gas flows into the inlet manifold, bypassing - but not fully - the exhaust side of the turbo which reducing emissions as a result - how, I don't quite know but apparently it does. As a result of this diversion there are less exhaust gases spinning the exhaust side of the turbo and therefore less spinning of the turbine and so less air being fed to the engine.
Because the air coming out of the turbo is pressurised it is hot - how hot I don't know - but apparently not as hot as the exhaust gases because supposedly as a result of the EGR diverting exhaust gases into the inlet, the combustion chamber temperature is reduced. This means cooler exhaust gases leave the engine and therefore cooler through the turbo. That's the theory at least!

Blanking the EGR valve means that the gases flowing through the turbo are always as hot as those in the combustion chamber.

Now, it may be the case that this isn't a problem in JTD engines but in the Renault DCi engine I had, it was and the turbo or part of it (seals maybe) overheated and the turbo popped. The EGR valve in those engines fails closed, leaving the EGR valve permanently shut - which is the same condition as blanking the EGR inlet/outlet - hence my original question.

 

[hdseven]

Sorry to go off topic, but how easy is it to blank off? As in time and cost?

yes easy, cut a piece of tin using original gasket as template and just put too holes in it for the bolts to pass through.
its at the top right rear of engine just under engine cover

it wont knacker ur turbo so dont worrry............am not going into more detail about that, but egr as NOTHING to do with how a turbo works...........it actualy warms the engine quicker and reduces NOX levels by upto 70%

Gary

 

[hdseven]

In normal operation it shouldn't affect the turbo too much. But since turbos are driven by exhaust gases, it does have a bearing on how the turbo operates.

Basically - exhaust gases leave the engine via the exhaust manifold and through one section of the turbo which spins a turbine linked via a shaft to the other section which forces air (via the intercooler) into the engine.
The EGR valve is connected by a branch off the exhaust manifold before the turbo and under low boost levels (<30% or thereabouts I believe) it is open which means exhaust gas flows into the inlet manifold, bypassing - but not fully - the exhaust side of the turbo which reducing emissions as a result - how, I don't quite know but apparently it does. As a result of this diversion there are less exhaust gases spinning the exhaust side of the turbo and therefore less spinning of the turbine and so less air being fed to the engine.
Because the air coming out of the turbo is pressurised it is hot - how hot I don't know - but apparently not as hot as the exhaust gases because supposedly as a result of the EGR diverting exhaust gases into the inlet, the combustion chamber temperature is reduced. This means cooler exhaust gases leave the engine and therefore cooler through the turbo. That's the theory at least!

Blanking the EGR valve means that the gases flowing through the turbo are always as hot as those in the combustion chamber.


Now, it may be the case that this isn't a problem in JTD engines but in the Renault DCi engine I had, it was and the turbo or part of it (seals maybe) overheated and the turbo popped. The EGR valve in those engines fails closed, leaving the EGR valve permanently shut - which is the same condition as blanking the EGR inlet/outlet - hence my original question.

some of that is sooooo far off the mark

and this is just sooooooo wrong
"supposedly as a result of the EGR diverting exhaust gases into the inlet, the combustion chamber temperature is reduced. This means cooler exhaust gases leave the engine and therefore cooler through the turbo. That's the theory at least!"
the warm air in the combustion chamber helps lower the combustion temp, that means the diesel ignites easier! and that means less nox produced, and in no way does it make exhaust gasses cooler for running thought turbo.....they are no where near as hot as petrol one anyway, and the exhaust would be as hot either with or without a turbo

"Now, it may be the case that this isn't a problem in JTD engines but in the Renault DCi engine I had, it was and the turbo or part of it (seals maybe) overheated and the turbo popped. The EGR valve in those engines fails closed, leaving the EGR valve permanently shut - which is the same condition as blanking the EGR inlet/outlet - hence my original question"
ok.......that comment.......erm where to begin.......a turbo shaft spins on a film of oil....that is pumped into the turbo and then back out and round the engine so that helps keep the shaft at a nice temp, what happens when oil cant get it the shaft warms up dramaticly, oil burns away, shaft comes into contact with journal bearings and jams as itll be running out of axis and then snaps, worn seals (piston rings) will make a very smokey engine long befor the turbo fails, so u see nothing to do with egr as the sole thing the turbo spins on is OIL

Gary

 

[bobda]

But one of the selling points (if you can call it that) of an EGR valve is that by diverting exhaust gases into the inlet, the combustion chamber temperature is reduced isn't it?

I've seen posts saying that the EGR valve in JTD engines is used as a dump valve to reduce the volume of exhaust gases entering the turbo at what would be high engine RPM. That's the exact condition in which my turbo failed in the DCi engine.

I think you can gather that I'm not a mechanic, just trying to prevent another turbo blowing up on me!

ok.......that comment.......erm where to begin.......a turbo shaft spins on a film of oil....that is pumped into the turbo and then back out and round the engine so that helps keep the shaft at a nice temp, what happens when oil cant get it the shaft warms up dramaticly, oil burns away, shaft comes into contact with journal bearings and jams as itll be running out of axis and then snaps, worn seals (piston rings) will make a very smokey engine long befor the turbo fails, so u see nothing to do with egr as the sole thing the turbo spins on is OIL

Trust me, my turbo failed! Something popped internally and dumped oil into the exhaust side of the turbo and out of the exhaust. It was nothing to do with the engine.

 

[bear1]

Turbos fail however, theres no way to tell if the turbo failed cause of the EGR. The valve is mostly there just to reduce what comes out of the exhaust. You can blank the egr, and as said it wont have any effect on the turbo.. in fact from what i heard its better with it blanked than without i just dont want to mess with it. and it can affect performance but only low down, so 1st 2nd would have much less lag.
If you are unsure or afraid your turbo will let go then just leave it the way it is...