EGR blanking

[Petemate]

I know this is mentioned elsewhere in the forum but I've gone 'model-specific' for a reason. (namely I have yearnings for either a Passat or A4 '96-on) Can one simply blank off the EGR (much the same as I have done with my R**er 45 TDi) and leave the rest of it 'thinking' that it is doing a 'good' job? ie, still connected to the cooling system thereby not affecting warm-up but not chucking all the cr*p into the inlet, and not resulting in either a light popping up or worse the car going into'limp' mode?
Lots of info on this sort of thing in the MG-Rover forum but different VAG models seem to have their own aspects in this matter. I have seen pics of the insides of some VAG inlet manifolds which are scary, and my own experience with the 45 is that since blanking the EGR off (soon after I got it nearly three years ago) the manifold has actually become cleaner over a period. I checked it when I blanked the valve off and it was a bit grubby in there, and thought that I would eventually do it but not there and then as one needs to move the exh manifold to get the inlet off, but recently I had a look in there and it has cleared of nearly all of the deposits.
Pete

[martin1810]

You have posted in the wrong section really. The b6 has alot of electronics. If you post in the b5 section you will get replies from people who have done it, if any have. I see no reason why you can't block the egr on early models. VW claim that later models need the egr working as the ecu has to take this into account when fueling. I guess you may have to try for yourself.

[Petemate]

Thanks Martin for the quick response. Do I take it that the B6 is the 'face-lift' with the different head and tail lights? Cos those are the ones that take my fancy. Now I can see what you mean by electronics, and that VW have indicated that the EGR needs to be working for the fuelling, but if it is just blanked off surely this should not affect signals back to the ECU? Or am I out of my depth here.... Would it be possible for the ECU to detect that the valve is blanked given that the electrics & vacuum are still connected? I know that on some very late model Rovers, where some owners have merely either pulled off and blocked the vac, or just disconnected the plug, it results in a fault code display.
Pete

[martin1810]

The b6 is the current shape passat. Came in during 2005. Not a facelift but a completely new car. The problem with modern diesels and EGR valves is that some smart person has programmed the ecu in advance. This takes into account the fact that at different revs, different amount of preburnt exhaust gases will be "rebreathed" by the engine. By blanking off the EGR you are changing a condition which the ECU will not know about. The end result may be wrong fueling. This didn't seem to matter on old models and maybe still doesn't matter BUT not many people seem to want to risk trying it to find out. I think that if I had an EGR fault that was going to be expensive to fix, I might try blanking it to see what happens but as long as the EGR is ok I wouldn't bother.

[Petemate]

Thanks Martin - seems like sound advice. Shame that 'progress' seems to cut down our options but I guess that's the way it is. So every now and then with the later models it will be a clean-out of the inlet manifold and at worst an expensive EGR replacement. I would love to get hold of that 'smart person' and shake him/her till their brains fell out!
Pete

[martin1810]

Forgot to say...EGR is actuated from a solenoid valve block which is all electronic and reports to the ecu. It is way more complicated than on old cars.

[Petemate]

Forgot to say...EGR is actuated from a solenoid valve block which is all electronic and reports to the ecu. It is way more complicated than on old cars.

I can follow that Martin. But if the EGR and all its connections are left intact, and the valve merely blanked, how would the ECU know? Or is it that the ECU detects and/or controls the amount of exhaust gases that are passed into the inlet?
Pete

[martin1810]

Not sure what the ecu does but it does connect to the EGR directly and again indirectly via the solenoid block (vacuum system). I think the main problem with blanking the egr is that the ecu is calculating air and fuel on the basis that it is open. I have seen claims that this means the Exhaust gases effect the air temperature going into the cylinders and that the gas contents effect the overal performance of combustion. I think most people are leaving these cars fairly standard at present. As they get older people will probably start to play.

[Petemate]

I think the main problem with blanking the egr is that the ecu is calculating air and fuel on the basis that it is open. I have seen claims that this means the Exhaust gases effect the air temperature going into the cylinders and that the gas contents effect the overal performance of combustion. As they get older people will probably start to play.

Yep - best left alone then on the later cars.
Ta again
Pete