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

[mattl]

Any idea on the combustion temps that a non egr car reaches versus a car with a functioning EGR and how it compares to combustion temps on a turbo petrol?

[BigRuss]

Wouldn't like to comment on the combustion temperature differences between egr equipped vehicles and those without as it is not only down to that. It's also down to any modification, condition and tune of the vehicle.

Exhaust gas temps for a turbo diesel car should be between 650 and 800 degrees C under full load conditions.
The petrol turbo cars should be between 700 and 900 Degrees C under the same conditions.

Turbochargers will start too cook over 900 degrees C

The best way to minimise combustion temperature is to make the inlet charge as cold as possible. If your intercooler is semi-clogged then it isn't going to be as effective.

I've run turbocharged cars both petrol and diesel since they were first available the first being a B type engined SAAB 900 with an mechanical wastegate. (rather than the later variable type). I also currently have a Citroen Activa CT. I've run them in various states of tune and have never had a turbo fail due to overheating.
The only turbo failure that I've had has been due to poor maintainence of the oil by a previous owner.


Russ

[BigRuss]

Just found some more info. see: http://www.ias.ac.in/sadhana/Pdf2004Jun/Pe1131.pdf

On studies between egr at 0% and 21% open at different loads, show temperature differences of no more than 20 degrees C. to the exhaust gases. The effect on the combustion temperature therefore would not increase to over 900+ degrees C, that would do damage, unless there were other problems.

Egr systems also cause an increase of particulate matter(soot)that can have a detrimental effect on the engine and of expelled exhaust gases.

Russ

[Jules]

Great info chaps, the very reason I started this thread.
Seem to remember a while back someone on here did the Intake Mod and suffered a 3 BHP loss on the rolling road.

More interestingly, no one on here has reported any diesel engine failure with all the available tuning mods...............yet.

[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..

[Rincewind]

The whole EGR debate continues to rumble on.

I for one find it increasinly frustrating that there are so many people out there determined to by-pass them or turn them off etc when manufacturers spend so much time and effort getting them into vehicles to help reduce emissions with minimal impact on engine performance and so on.

I've just done some test work out in Italy on some diesel engines for emissions and fuel economy and also engine power and the results that I had with a "by-passed" EGR valve or failed unit as is would be viewed are amazing.

With the EGR valve working as it should the results were as follows:

CO - 0.306 g/km 41.3% of the limit for Type approval for this vehicle.
NOx - 0.323 g/km 82.8% of the limit for Type approval for this vehicle.
HC + NOx - 0.356 g/km 77.4% of the limit for Type approval for this vehicle.
PM - 0.026 g/km 52% of the limit for Type approval for this vehicle (particulate matter).

Then for OBD purposes, we have to fail the system or by-pass it to see if the system falls within the OBD limit requirements in this instance, it's fully open like a by-pass system would be.

The results are as follows (OBD limits are different, but look at what the TA limit comparison is) :

CO - 0.210 g/km 31.2% of limit. So far so good.
NOx - 1.783 g/km 457.2% of the limit - so massively over the limit!!!
HC + NOx - 1.859 g/km 404.1% of the limit - massively over the limit again
PM - 0.161 - 268% of the limit.

So as you can see, on a normal drive cycle for emissions testing the results go through the roof and are almost like running a vehicle from god knows how many years ago. Not to mention that the drivablility of the vehicle falls through the floor to begin with until the ECU "smooths" things out and then over a few cycles, the MIL will come on to show that there is a problem in the engine which is then stored in the memory until taken out and should you get pulled for a road side emissions check (which is starting to happen again very soon) they will be able to access your ECU and find out how far you've driven with a defecive EGR valve or other.

Fuel consumption also suffers on Phase 1 of the test by up to 1 litre in the urban cycle.

Keeping it clean is always a good thing as it improved efficiency, but bypassing it is a real no no in my books. MOT emissions sniffs are just that, sniffs and if you were to put your car through a proper emissions test like the one's I have to witness for type approval, your car would fail the emissions test. for either Euro III which all of our cars are type approved to and they wouldn't even get close for Euro IV.

Yes, they are predominantly there for emissions, but given the lengths manufacturers go to fit them into the engines and callibrate them etc with minimal impact on performance costs thousands and many months of development so I hope you can begin to understand why I and my fellow engineers who deal with engine development get totally hacked off when people start by-passing them all for the sake of a few BHP which you're never really going to notice.

Sorry, my 2p's worth but from where I sit, they're there for a very important reason. I hope you understand my frustration.

Nic

[JohnDotCom]

Everyone is entitled to their Opinion Rincewind (Nic) that is what this forum is all about.
You make some very Valid points,
But the modifications I have now made to my car give me 170BHP on the Rolling Road Tests and give the Car the power I like and it deserves.
I personally don't give a Hoot about Emissions (could be because I'm in the states so much),
If I get ripped off and have to pay all these green taxes then I will do as I see fit.
Only my personnel opinion of course, I don't recycle either.
Oops thats me off most peoples Christmas Card list.

Nothing listed on E4 either and no MIL Light.
Just sailed through MOT with ReMap, Rons Synergy, Air Intake Mod etc.
I have not de - cat it yet though.

[Zeb]

I take your points Rincewind, however, many people with the egr bypass have non standard engines anyway. eg. Roverron module. Secondly, most people haven't fitted it for bhp but as a way of reducing smoke levels and to avoid reliability issues of what is, after all, an old-fashioned vacuum operated system that clogs up.

John, you will be lynched by the tree huggers...

[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.

[Rincewind]

Originally Posted by JohnDotCom

Everyone is entitled to their Opinion Rincewind (Nic) that is what this forum is all about.
You make some very Valid points,
But the modifications I have now made to my car give me 170BHP on the Rolling Road Tests and give the Car the power I like and it deserves.
I personally don't give a Hoot about Emissions (could be because I'm in the states so much),
If I get ripped off and have to pay all these green taxes then I will do as I see fit.
Only my personnel opinion of course, I don't recycle either.
Oops thats me off most peoples Christmas Card list.

Nothing listed on E4 either and no MIL Light.
Just sailed through MOT with ReMap, Rons Synergy, Air Intake Mod etc.
I have not de - cat it yet though.

I know - sorry just having one of those mornings where I could happily grab the nearest person and rip their throat out for asking SFQ's as we call them (Silly Effing Questions as we call them) and some have been emissions related.

I'm not the greenest person out there at all and I do appreciate where you're coming from, it's just one of those niggly points that get's me back up a bit every now and then. I'm the first one (money permitting) in the queue for a V8 monster or whatever.

MOT is a breeze and any vehicle that's been maintained properly will walk it esp on the smoke side as the tolerance is quite high, but an MOT unit is not quite as sensitive as a full blown Horiba lab and AVL smoke meter plumbed in.

I'm going down the Rover Ron route soon but only up to about 150 bhp as I don't trust the bottom end on the 204D2 engine that we have in our cars to take the 170 bhp over a long period of time (hence the reason why Land Rover got the 204D3 engine IIRC that was a bit stronger).

Not getting at anyone, it's just the whole EGR things that makes me growl a bit.