I

iand1967

New Member
hi all we all no that the egr valve is there to do a job, and in my opinion it is just a useless bit of kit which goes about its job very badly and most of us disable them as i have, and yes it does run better, however i have been looking around the net and apparently it is very bad to disable the egr valve on turbo diesels as it causes overheating of the turbo and combustion chamber leading to expensive problems can anyone shed any light on this
thanks Ian
 
The problem with a diesel is that it can run lean very easily because of the way they are designed, but using the exhaust gasses to run back in to the system you will reburn the un burnt fuel in the mixture.
 
Treev150 said:
The problem with a diesel is that it can run lean very easily because of the way they are designed, but using the exhaust gasses to run back in to the system you will reburn the un burnt fuel in the mixture.
Click to expand...
Why dont you spend some time learning about Diesel engine theory before making statements like this ? Its not like the info is hard to find,Diesels are meant to run an excess of air - if they dont they go quickly into black smoke territory.And by the way EGR systems need to be left alone - or worked on by people who know what they are doing.I am not ranting - just stating fact.
 
run an excess of air??? wtf?????

Granted the mixture is leener than petrol, but If the mixture is wrong it will still go tits up!
 
interesting points from the two of you there, im coming around to the conclusion the egr is best left alone even if it is going to send that oily ****y mess into the inlet tract after all i suppose you can clean out the pipes etc., better than a melt down i think.
 
Treev150 said:
Lets just agree to disagree shall we?
Click to expand...
No ! read the book,direct injection engines run at the smoke limit with an air excess of 40- 50%.Info direct from Bosch,as for the crap in the manifold - so what ? A properly functioning EGR system can reduce Nox emissions by up to 80% - as the main cause of acid rain I fail to see how removing it is a desirable thing to do.
 
Some one's getting upset.....

My point is

You say that you run with 40 - 50% excess of air, if this is running at for example 80 - 90%, will it still run ok?
 
Not getting upset - I only lose my rag with politicians ! Just trying to get you to to understand diesel theory.The 40-50% is straight from the Bosch diesel engine management book,not me.
If you think about the inlet tract of a diesel there is no throttle butterfly as on a petrol engine,so there is no control of the mass of air injested.The only control is of maximum boost pressure on a turbo engine at high engine speeds/loads.In the past some diesels had throttle butterflys,this was for 2 reasons.The first was for vacuum governed injector pumps - they had a diaphram operated from the difference in depression either side of the butterfly.The second was to create a depression in the inlet to provide vacuum for a brake servo.Series 111 Lr 2.1/4 diesels were the last things I can recall seeing this on.
Neither of the above had anything to do with fuel air mixture as with a petrol engine where everything is done to keep the air/fuel ratio at 14.7/1 (lambda) which is the best compromise of power and emissions.With a diesel you inject more fuel -it speeds up/ makes more torque,you just need to ensure there is more than enough air to burn with it.Sorry if I'm not explaining it very well - I only fix them,I'm not a teacher - nor much good at typing !!!!
 
Yes i do understand exactly what you are saying, but my point is that if you don't put enough fuel in it will not run right,

I was not clear when i spoke before, as not enough fuel can also been seen as too much air, i think it was at this point we got our wires crossed.

But we got there in the end as i totally agree with your above statement.
 
so can we take it that the egr valve is best left alone and all this c-ap we see about shoving ball bearings up pipes etc. is no the way ahead the guys
 
Well said,if it needs all sorts of stuff to bodge it up why have it in the first place? It's there for a reason, if you have problems guys get them sorted properly. I've spent the greater part of my working life in operations positions for a major oil refinery, anything that burns needs air (02) the critical thing for efficiency is controlling the ratio of 02 to fuel, that is why these devices are there, filling them full of junk is a short term and
eventually expensive bodge.
It's also an attempt by some manufacturers to lessen the amount of c--p (ie unburnt fuel) that gets stuffed into the atmosphere.

By the way everything works "in theory" but in the real world.......??
 
Whilst i can see the enviromentalists theory for leaving the EGR valve in place, try disconnecting it and see how your car runs.

I have disconnected the one on my wifes TD4 for the last 12 months and it has ran much better with it blocked off than connected, even she noticed the car 'Felt' better after i had done it and she is one of them women who puts the key in and expects it to start.

The car even ran lower emmissions on its MOT with it disconnected :D it also passed with it un-blocked but with a higher reading but in my case it stays blocked off.

Zippy
 
thats all well and good zippy, i agree my lany runs better with the egr blocked of but you run the risk of overheating the combustion chambers and turbo and as i use my car for towing im going to leave my egr valve to do its job and avoid the expensive repair bill !!!!!!
 
The EGR valve is there to comply with reduced emissions which has a detrimental effect on performance, without it the unused Exhaust Gas goes out to atmosphere.

Without it your engine will always be breathing clean air not Recirculated, clean induction air will always be colder and as a result denser which = better combustion.

As i've already said its your engine and your choice what you choose to do, i've chosen mine and thats the way it will stay.
 
Without it your engine will always be breathing clean air not Recirculated, clean induction air will always be colder and as a result denser which = better combustion.this was covered on the bmw site now i dont no but apparently its not the temp of the air going in that counts but the level of o2 and it goes without saying recycled gas has less o2 than normal air but normal air burns hotter hence the rise in combustion temp and a hotter turbo.
 
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