Possible Renault EGR valve solution?
Discussion
Hi All,
I started a thread in General gassing that subsequently was moved to french bred about the usual Renault EGR valve woes (on an espace 2.2dci). I had an idea as my last post on that topic (see below) and thought that this may be a better place for advice/thoughts from you technical bods.
Having thought about the whole EGR valve issue I have seen suggestions on other forums as to blanking the EGR valve off and there have been many replies advising against this. It would appear in many cases this has been a success but no long term tests - so a bit of an unknown.
As I understand the valve recirculates exhaust gases back into the induction system to be re-burnt for environmental/cooling reasons.
I am not sure if a specific gas is extracted to be recirculated such as carbon dioxide or monoxide but suspect it just normal exhaust gases hence the soot and carbon collecting and clogging up the EGR valve.
It is also suggested that this gas is used for cooling purposes in the cylinders and any removal of the EGR valve would be detrimental to this with consequences for the turbo to overheat etc.
Now at the moment I am more concerened with having a functioning engine than reduction of carbon dioxide (rightly or wrongly) but would have concerns removing/blankijng off the EGR valve system totally.
My idea would be to cap the exhaust gas feed to the valve off removing the pipe and provide an air intake with filter to the EGR valve where the exhaust gas would have previously been. The thought behind this is that the ECU gets to operate the EGR valve and it has a supply of cool gas ie air (which must be cooler than the re-circulated exhaust gas) to feed into the induction system. Also there would be no clogging up of the EGR valve with soot and carbon.
Any thoughts on the above would be appreciated and please feel free to tell me if I am talking nonsense.
I started a thread in General gassing that subsequently was moved to french bred about the usual Renault EGR valve woes (on an espace 2.2dci). I had an idea as my last post on that topic (see below) and thought that this may be a better place for advice/thoughts from you technical bods.
Having thought about the whole EGR valve issue I have seen suggestions on other forums as to blanking the EGR valve off and there have been many replies advising against this. It would appear in many cases this has been a success but no long term tests - so a bit of an unknown.
As I understand the valve recirculates exhaust gases back into the induction system to be re-burnt for environmental/cooling reasons.
I am not sure if a specific gas is extracted to be recirculated such as carbon dioxide or monoxide but suspect it just normal exhaust gases hence the soot and carbon collecting and clogging up the EGR valve.
It is also suggested that this gas is used for cooling purposes in the cylinders and any removal of the EGR valve would be detrimental to this with consequences for the turbo to overheat etc.
Now at the moment I am more concerened with having a functioning engine than reduction of carbon dioxide (rightly or wrongly) but would have concerns removing/blankijng off the EGR valve system totally.
My idea would be to cap the exhaust gas feed to the valve off removing the pipe and provide an air intake with filter to the EGR valve where the exhaust gas would have previously been. The thought behind this is that the ECU gets to operate the EGR valve and it has a supply of cool gas ie air (which must be cooler than the re-circulated exhaust gas) to feed into the induction system. Also there would be no clogging up of the EGR valve with soot and carbon.
Any thoughts on the above would be appreciated and please feel free to tell me if I am talking nonsense.
Doug Shep said:
As I understand the valve recirculates exhaust gases back into the induction system to be re-burnt for environmental/cooling reasons.
I am not sure if a specific gas is extracted to be recirculated such as carbon dioxide or monoxide but suspect it just normal exhaust gases hence the soot and carbon collecting and clogging up the EGR valve.
It is also suggested that this gas is used for cooling purposes in the cylinders and any removal of the EGR valve would be detrimental to this with consequences for the turbo to overheat etc.
Now at the moment I am more concerened with having a functioning engine than reduction of carbon dioxide (rightly or wrongly) but would have concerns removing/blankijng off the EGR valve system totally.
My idea would be to cap the exhaust gas feed to the valve off removing the pipe and provide an air intake with filter to the EGR valve where the exhaust gas would have previously been. The thought behind this is that the ECU gets to operate the EGR valve and it has a supply of cool gas ie air (which must be cooler than the re-circulated exhaust gas) to feed into the induction system. Also there would be no clogging up of the EGR valve with soot and carbon.
Any thoughts on the above would be appreciated and please feel free to tell me if I am talking nonsense.
Diesel EGR is there to lower NOx. I am not sure if a specific gas is extracted to be recirculated such as carbon dioxide or monoxide but suspect it just normal exhaust gases hence the soot and carbon collecting and clogging up the EGR valve.
It is also suggested that this gas is used for cooling purposes in the cylinders and any removal of the EGR valve would be detrimental to this with consequences for the turbo to overheat etc.
Now at the moment I am more concerened with having a functioning engine than reduction of carbon dioxide (rightly or wrongly) but would have concerns removing/blankijng off the EGR valve system totally.
My idea would be to cap the exhaust gas feed to the valve off removing the pipe and provide an air intake with filter to the EGR valve where the exhaust gas would have previously been. The thought behind this is that the ECU gets to operate the EGR valve and it has a supply of cool gas ie air (which must be cooler than the re-circulated exhaust gas) to feed into the induction system. Also there would be no clogging up of the EGR valve with soot and carbon.
Any thoughts on the above would be appreciated and please feel free to tell me if I am talking nonsense.
If you were to put a fresh air feed in you would want to do so from the post intercooled air and not simply fresh air to avoid issues with potential loss of boost.
The complications that may arise would be if there were signal levels expected by the ECU from temperature sensors and pressure sensors, which may bring on a derate if they detect a signal out of range or out of the expected region.
Also if the engine is modified that could also affect insurance coverage.
If you can please post some pictures of the engine, sensors and any schematics from a workshop manual and we can figure out if this is doable.
Thankyou for the reply that has some interesting points.
I am by no means mechanically minded and my post above looks at things in simplistic terms, and this is just the sort of input required.
With regard to your point of feeding the EGR valve with carge cooled air is this because otherwise is the EGR valve opened with only a filter to fresh air it would blow out?
On the honest John site it also suggests that gases from the exhaust that the EGR valve feeds are use for cooling purposes as well in the cylinders, but I am not sure on this as surely exhuast gaese are hot?
I am capable of taking a few pictures of the induction system and EGR valve on my 2.2Dci but as far as schematics and location of senors I am afraid I will be a bit lost.
I am by no means mechanically minded and my post above looks at things in simplistic terms, and this is just the sort of input required.
With regard to your point of feeding the EGR valve with carge cooled air is this because otherwise is the EGR valve opened with only a filter to fresh air it would blow out?
On the honest John site it also suggests that gases from the exhaust that the EGR valve feeds are use for cooling purposes as well in the cylinders, but I am not sure on this as surely exhuast gaese are hot?
I am capable of taking a few pictures of the induction system and EGR valve on my 2.2Dci but as far as schematics and location of senors I am afraid I will be a bit lost.
Doug Shep said:
On the honest John site it also suggests that gases from the exhaust that the EGR valve feeds are use for cooling purposes as well in the cylinders, but I am not sure on this as surely exhuast gaese are hot?
The cooling side of things isn't cooling in the conventional way you're thinking it is. By reusing some exhaust gas an inert gas is being mixed with the fresh charge. This inert gas doesn't burn with the diesel, this in effect reduces the engine capacity as say 20% of the charge may be inert gas which doesn't combust! Therefore this reduces the heat generated by combustion.By removing the egr, at operating points when the engine thinks its getting say 80% air and 20% exhaust it will be getting 100% air. This will cause it to run lean, reducing power. However, as typically egr is only used at part throttle you can overcome this by slightly increasing your accelerator position. The only problems really will be tricking the engine into thinking the egr is still connected so it doesn't go into a limp home mode! To do this, as said previously, we need to know what sensors are monitoring the egr system.
Doug Shep said:
With regard to your point of feeding the EGR valve with carge cooled air is this because otherwise is the EGR valve opened with only a filter to fresh air it would blow out?
It could well do so. There are pressure dynamics in the induction and EGR system that have been very carefully set up and use of a filter could undo all of that and make the engine not work. Going about it this way at least gives you a good chance of success.Doug Shep said:
On the honest John site it also suggests that gases from the exhaust that the EGR valve feeds are use for cooling purposes as well in the cylinders, but I am not sure on this as surely exhuast gaese are hot?
Cooling is all relative, I would say it is more along the lines of preventing the engine from generating too much heat. If egr is present air won't be so that limits how much fuel the engine can combust.Doug Shep said:
I am capable of taking a few pictures of the induction system and EGR valve on my 2.2Dci but as far as schematics and location of senors I am afraid I will be a bit lost.
We need good detailed photos of all the parts with covers removed. Schematics from a Haynes manual would be useful. Just do the best you can.syncro. said:
By removing the egr, at operating points when the engine thinks its getting say 80% air and 20% exhaust it will be getting 100% air. This will cause it to run lean, reducing power. However, as typically egr is only used at part throttle you can overcome this by slightly increasing your accelerator position. The only problems really will be tricking the engine into thinking the egr is still connected so it doesn't go into a limp home mode! To do this, as said previously, we need to know what sensors are monitoring the egr system.
Running lean won't make any sigificant difference on a diesel, aside from the NOx emissions issue.Soory for the lack of reply however family duties called.
The car is in the garage today with the oil leak, suspected clogged EGR valve and turbo sensor fault so I am awaiting the dreaded call!
I do no have a Haynes Manual for the espace however I will source one shortly and post pics when I get the car returned - will also try to find out the parameters used to open/close the EGR valve and position/type of sensors.
The car is in the garage today with the oil leak, suspected clogged EGR valve and turbo sensor fault so I am awaiting the dreaded call!
I do no have a Haynes Manual for the espace however I will source one shortly and post pics when I get the car returned - will also try to find out the parameters used to open/close the EGR valve and position/type of sensors.
Got the car back from the garage and as I had initially thought the source of oil was through the turbo bearing seals.
Very dissapointed with this as this is as I had suggested when the car went to the first garage many months ago only to be assured that turbos don't go on this model and was the EGR valve drawing all the oil through.
It appears from my initial research that the EGR valve in this case (renault) is solenoid operated by the CPU from measurement of air flow. This seems a bit rudementry to me and I need to find where this sensor is positioned.
Very dissapointed with this as this is as I had suggested when the car went to the first garage many months ago only to be assured that turbos don't go on this model and was the EGR valve drawing all the oil through.
It appears from my initial research that the EGR valve in this case (renault) is solenoid operated by the CPU from measurement of air flow. This seems a bit rudementry to me and I need to find where this sensor is positioned.
Doug Shep said:
Got the car back from the garage and as I had initially thought the source of oil was through the turbo bearing seals.
Very dissapointed with this as this is as I had suggested when the car went to the first garage many months ago only to be assured that turbos don't go on this model and was the EGR valve drawing all the oil through.
It appears from my initial research that the EGR valve in this case (renault) is solenoid operated by the CPU from measurement of air flow. This seems a bit rudementry to me and I need to find where this sensor is positioned.
I hope the garage cleared the turbo drain tube as that can cause much the same issue as seals that are worn. I would have them show you how they diagnosed the turbo as having a seal leak and not a drain tube fault.Very dissapointed with this as this is as I had suggested when the car went to the first garage many months ago only to be assured that turbos don't go on this model and was the EGR valve drawing all the oil through.
It appears from my initial research that the EGR valve in this case (renault) is solenoid operated by the CPU from measurement of air flow. This seems a bit rudementry to me and I need to find where this sensor is positioned.
The EGR valve is probably driven by the MAF sensor, plus pedal position plus engine speed.
As I understand the outlet hose was disconnected and the oil was being blown out of the turbo oulet - I will however unsure that the drain tube be checked as the turbo itself does not sound as if the bearings have gone as previously commented by another garage (who did not phsically look at it though)
I have the car back and have not been given a quote as yet though I am expecting around £600 for the turbo and the rest if needed, I will ensure that the EGR valve is in good order though it was found to be fine yesterday and will get it fully serviced at the same time with an engine flush and fully synthetic oil.
Thanks for the heads up and info on the EGR valve operation I will keep you udated.
Having thought about it perhaps the oil around the engine bay (top) was coming out of the drain tube?
I have the car back and have not been given a quote as yet though I am expecting around £600 for the turbo and the rest if needed, I will ensure that the EGR valve is in good order though it was found to be fine yesterday and will get it fully serviced at the same time with an engine flush and fully synthetic oil.
Thanks for the heads up and info on the EGR valve operation I will keep you udated.
Having thought about it perhaps the oil around the engine bay (top) was coming out of the drain tube?
Edited by Doug Shep on Tuesday 12th January 11:42
Good Morning All,
A quick update - the garage are doing sterling work and it would appear following a strip down that it was not the turbo etc.
Oil leak over the engine was a poorly secured pipe - sorted, however they are rapidly running ut of ideas how the oil is getting in the system and there is a problem with back pressure from the turbo I believe.
The inlet manifold has been replaced, the engine compression tested (fine) and the turbo drain being checked again (however this was thought to be unlikely).
I suggested that could some kind of blockage or restriction in the exhaust or Cat is this feasible?
A quick update - the garage are doing sterling work and it would appear following a strip down that it was not the turbo etc.
Oil leak over the engine was a poorly secured pipe - sorted, however they are rapidly running ut of ideas how the oil is getting in the system and there is a problem with back pressure from the turbo I believe.
The inlet manifold has been replaced, the engine compression tested (fine) and the turbo drain being checked again (however this was thought to be unlikely).
I suggested that could some kind of blockage or restriction in the exhaust or Cat is this feasible?
Doug Shep said:
Good Morning All,
A quick update - the garage are doing sterling work and it would appear following a strip down that it was not the turbo etc.
Oil leak over the engine was a poorly secured pipe - sorted, however they are rapidly running ut of ideas how the oil is getting in the system and there is a problem with back pressure from the turbo I believe.
The inlet manifold has been replaced, the engine compression tested (fine) and the turbo drain being checked again (however this was thought to be unlikely).
I suggested that could some kind of blockage or restriction in the exhaust or Cat is this feasible?
When the turbo drain gets blocked the rate at which the oil flow goes in does not match the rate at which it can flow out - end result is that it comes out of the shaft seals.A quick update - the garage are doing sterling work and it would appear following a strip down that it was not the turbo etc.
Oil leak over the engine was a poorly secured pipe - sorted, however they are rapidly running ut of ideas how the oil is getting in the system and there is a problem with back pressure from the turbo I believe.
The inlet manifold has been replaced, the engine compression tested (fine) and the turbo drain being checked again (however this was thought to be unlikely).
I suggested that could some kind of blockage or restriction in the exhaust or Cat is this feasible?
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