More on the EGR Bypass Valve....Modify or Leave alone

[Zeb]

Originally Posted by ColinW

I have never heard so much garbage talked on this forum about the EGR valve. I am so suprised that droves of R75 lemmings are heading for the cliffs, (And has anyone here been rude about you? No, your opinion, whilst valid, is not the only one.) based on half truths and mis-information, to the extent that they are removing a crucial bit of automotive design (So crucial they have only in recent years been added to engines?- 1970s I think? So crucial that if it fails there is no warning indicator to avoid damage to the turbo? So crucial the acronym for it is Exhaust Gas Recirculation system rather than Combustion Cooling System?), in the mistaken belief it is costing them a few HP.

There seems to be this idea that the introduction of a small percentaqe of exhaust gases into the inducted air is going to increase the air temperature and not cool it, as Honest John & others have suggested.

IT HAS NOTHING TO DO WITH AIR INTAKE TEMEPERATURE!

IT HAS ALL TO DO WITH COMBUSTION TEMPERATURES - IN THE CYLINDER!

You don't need to shout, we aren't morons...

It is a great pity the majority of forumites do not understand the chemistry of combustion in a diesel engine. Possibly...more likely we are talking physics here though..

The fuel takes as much oxygen as it needs. At low revs there is a surplus of oxygen, such that the flame temperature starts increasing as the fuel/air mix gets more diluted. Er, so temperature goes up as fuel/air mix gets diluted? By what?Ultimately, this produces Nitrogen Oxides (NOX), which are not only toxic , but are bad for the environment.

The introduction of exhaust gases, which are low in oxgen, dilute the oxygen in the cylinder, thus reducing the combustion temperatures. Maybe so but the exhaust gases are also hotter than cold air.

The suggestion that turbo bearings etc can be affected by these increased temperatures is perfectly valid. Even exhaust valves could be at risk. Can't see the temp difference being that extreme myself.

People have suggested that disabling the EGR doesn't affect the MOT emmisions. This is only because they are done at max revs, where most of the oxygen gets used up correctly, so it is low in NOX's.

The other misconception is when the EGR valve actually operates. It is supposed to be closed at idle, otherwise there can be erratic idling, which I'm sure a few suffer from.
However under full acceleration (wide open throttle), it should NOT be open also. At cruising where the engine is operating more effeciently then the valve should open, as controlled by the ECU.

So it is quite possible that by removing the EGR, cruising fuel consumption could be compromised. Consumption is reduced due to not introducing rogue elements into the combustion process in order to make the exhaust gases cleaner..

So why many people are prepared to pay good money for EGR by-pass tubes (tubes?), for the sake of an indeterminate increaser in power is beyond me. Although I will accept that at wide open throttle, then the marginal restriction could lose a few HP- big deal. People pay good money because these engines and tuned engines are restricted by a lack of oxygen, the restriction is not marginal by any sense and the result of bypassing the egr is far less smoke and a wee bit more power....oh and better mpg due to increased efficiency

Leave well alone, but clean reguarly. Mebbe not...

Colin

Sorry, having done some reading and thinking and driving...I disagree...IMHO natch..

Further reading....since it is obviously a hot topic elsewhere too:

http://www.dieselbob.co.uk/tips.shtml
http://www.wynns.be/news.aspx?l=EN&i...iArticleID=826
http://www.aa1car.com/library/egr.htm
http://forum.landrovernet.com/showthread.php?t=62808 (Bless 'em Page two is most enlightening!)
http://www.pistonheads.com/gassing/topic.asp?t=243418

None of these mention damage to the turbo btw..

[rollsey1]

Originally Posted by ColinW

So it is quite possible that by removing the EGR, cruising fuel consumption could be compromised.
Leave well alone, but clean reguarly.

Colin

Interesting. Anyone else had experience of reduced fuel consumption? My driving style and journey remain the same but my mpg has fallen a couple of notches (not good with current fuel prices!). I certainly haven’t had the +3 that Russ has (and I’ve carried out the air intake mod and PCV filter replacement).

When it gets a bit warmer I’m thinking of putting the original EGR back on to see if there’s any difference.

[Barnowlnoddy]

If it was good enough for the designers and builders, then so say I! Why some choose to question the design I have always had problems with. They must, after all, have spent valuable time and stood great costs to finish up with an engine with the all round capabilities of our Diesel. Mine stays has is and will receive the best attention from myself as and when needed - usually every 6 months regardless of mileage covered.

[Fishytroll66]

Thank you Colin, I have sat here reading and reading about this EGR lark and something simply did not add up..you have answered my question! I personally would rather remove and clean the OE EGR every few months than fit what is basically a tube.
EGR will be staying on mine foks...

[polinsteve]

Sounds a reasonable explanation. I really don't see the point in fiddling the EGR. It is there to reduce emissions and I'm sure that in real world driving, there will be no noticeable performance benefits.

[bl52krz]

Originally Posted by BigRuss

The whole statement seems to have a lot of flaws:

1. How can exhaust gasses (that the Egr lets in to the manifold) be cooler than the intake air?

2."On TDIs, EGR valve should open to allow carbon dioxide, which acts as a cooling gas) into the combustion chambers when the engine is under load (>30% boost)."
The whole idea of the Egr is to recirculate some of the exhaust gasses that are more likely to have a higher concentration of unburned fuel.(If you've ever tried to open an egr, it takes a lot of vacumn!)
Eg. on the over-run or if you accelerate too harshly.(throttle opening more than engine can draw in)

3."This can cause the engine to run on its crankcase oil until it is either stalled or goes bang." Of course a engine runs on its crankcase oil what other oil would it use!!!!
Unless he means the oil from the failed turbo bearings entering the induction system and being burnt, but that wouldn't cause your engine to go bang.
If it was that bad then the engine wouldn't run as the ECU would find it difficult to cope.
The Police would have stopped you way before then, for the amount of smoke you would be pumping out of the exhaust. I've had major bearing falure on a turbo and believe me you'd know about it!

4. Exhaust gasses reaching a temperature that would lead to failure of the turbo bearings. What's he running his diesels on???


The only part of this statement I agree with is that, an egr that is stuck partially open will cause rough running of the engine.


Does this guy know what he's talking about? I doubt it.

Egr bypasses make the engine more efficiant by increasing the amount of air that is entering the engine. It won't cause any of the problems described above. If I thought it would have any detrimental effect I certainly wouldn't have fitted one!


Russ

the meaning of "running on its crankcase gases (oil), seems old fashioned to me.
in the "old days", diesels that had not been serviced for a long time, could, under certain circumstances, carry on running when the "stop" cable was pulled. (old diesel drivers know what i mean)
they would also "run" backwards. i have had this happen to me.

[BigRuss]

Originally Posted by bl52krz

the meaning of "running on its crankcase gases (oil), seems old fashioned to me.
in the "old days", diesels that had not been serviced for a long time, could, under certain circumstances, carry on running when the "stop" cable was pulled. (old diesel drivers know what i mean)
they would also "run" backwards. i have had this happen to me.

Yes, I know it is possible under certain circumstances (I am an "long term" diesel owner) but usually you'd be aware there was something terribly wrong before it got to that state.

I was perhaps being a little sarcastic in the statement you quoted above

There has not been a scrap of evidence to suggest that fitting an EGR bypass or disabling the standard EGR will cause any problems to our cars as described in the original article.

In fact from some of the other information contained in this thread it could have a beneficial effect for the engine especially in relation to oil degradation.

Fitting a bypass or disabling the standard EGR (or not) is a matter of personal choice.

From personal experience I can say that having an EGR bypass fitted has had no detrimental effect whatsoever.

Coupled with the other tuning mods the engine will now happily rev to the limiter (if required) and returns both very good performance and economy.


Russ

[JohnDotCom]

Next step...remove limiter.............

[baggie9]

Originally Posted by JohnDotCom

Next step...remove limiter.............

Hi john ,whats the limiter ,my rev limiter cuts in at 3000rpm

[bl52krz]

Originally Posted by BigRuss

Yes, I know it is possible under certain circumstances (I am an "long term" diesel owner) but usually you'd be aware there was something terribly wrong before it got to that state.

I was perhaps being a little sarcastic in the statement you quoted above

There has not been a scrap of evidence to suggest that fitting an EGR bypass or disabling the standard EGR will cause any problems to our cars as described in the original article.

In fact from some of the other information contained in this thread it could have a beneficial effect for the engine especially in relation to oil degradation.

Fitting a bypass or disabling the standard EGR (or not) is a matter of personal choice.

From personal experience I can say that having an EGR bypass fitted has had no detrimental effect whatsoever.

Coupled with the other tuning mods the engine will now happily rev to the limiter (if required) and returns both very good performance and economy.


Russ

i thought you probably were being a bit sarky.
all i will say is, you pays your money and you take your choice.