EGR valve removal/bypass pollution effects

[charentejohn]

I know there is a lot of stuff about this but I wondered if anybody knows if bypassing the EGR makes a significant difference to the NOx output. I have been reading up and seems to me it could make a difference but not guaranteed. Just done this on my car Xantia HDI90 and massive performance increase, revs quickly below 3k which it never did before, also no smoke from exhaust.
All I have done is seal off the vaccuum pipe from the relay to the EGR valve rather than blanking off as a pain to get to. I believe mine is closed ok so with this disconnected it is like blanking it off.

I read somewhere, can't find it again, that NOx is produced at combustion temp of 2500c so wanted to know what an HDI temp was. Found these articles which were interesting.
Explanation of EGR and how it may or may not really work (actually an ad for an analyser) http://www.cambustion.com/products/egr" onclick="window.open(this.href);return false;
This is a really good explanation of how combustion works http://transportation.centennialcollege ... ls%204.pdf" onclick="window.open(this.href);return false; Interesting bit is half way down called 'Other Characteristics of DI Combustion' where it mentions how cold these engines run. People here have mentioned this before but interesting coments, they say if at tickover for a long time the temp will drop below operating temp and oil could be drawn past the pistons. Explains why a garage got clouds of grey smoke from mine after idling for a long time ?

From this I get the impression bypassing the EGR will increase NOx emissions at some times but reduce particulates as a tradeoff if it does. So if I leave it bypassed during an MOT it shouldn't make a real difference if they measure across the range of rpm/load as it would go up and down anyway ?

[citroenxm]

A clued up MOT tester will issue an ISNTANT MOT Fail if EGR or DPFs etc are missing or inop.. (SO Im led to beleve anyway!)

[evilally]

I haven't yet seen any specific legislation around EGR, although DPF is a hot topic right now. I wouldn't be surprised if similar MOT rules for EGR came to be soon given NOX is all over the news and the UK has some of worst NOX pollution in Europe, and NOX is now associated with all sorts of health problems. I must confess I removed the EGR on my 406 a couple of years back, mainly because it had caused horrendous coking of the inlet and valves. With that all cleaned up, the engine runs so much cleaner, although what it does to NOX I don't know. My understanding is that it only reduces NOX at idle or low engine loads, the majority of my driving is at 50-60mph.

With NOX and particulates now such a hot topic, and petrols becoming so much more economical, I can't see diesels being as popular in 5 years as they are now.

[charentejohn]

No problem disguising a blocked off EGR vac hose, I have some neat smooth tape (used to mask brickwork so sticks to anything and comes off cleanly) so can fit this to seal the pipe and push the hose back over it.

I am coming down on the petrol side myself, mainly as I understand them more. Parts seem cheaper and (avoiding DPF engines) there seems less to confuse me.
This is not a pollution issue as sad to say I think we are looking at environmental repair by reducing car emissions, as they say, disappearing in the rear view mirror.
I don't think they would know if it was not working as they cut in and out depending on temp and rpm ? so if the engine is reasonably ok it would probably pass anyway ?

I can't seem to find info on the NOx emissions at 2500C and what the actual temperature is when the fuel goes bang in the cylinder. If less than 2500C then no problem anyway ? seems this would only be relevant when on light cruising speed for EGR to open. Seems they all pollute, just pick which pollutant you want to lower. In time they will no doubt improve more but for now I will opt for a working car.

I did see they are trying to charge for 'polluting' vehicles in london with the aside of scrapping older (10yrs+) cars. Not sure the cost of pollution making a new car is less than running an older one for 10 yrs. To make a judgement take the difference between old and new engine pollution over 10 yrs and compare with pollution/energy used to make a new one.
Partly my thoughts on the changes made by EGR bypass, I don't to loads of miles so if bypassing means I produce 2% more NOx for the tiny time I am on light cruise or tickover does it make a real difference.

[Northern_Mike]

No problem disguising a blocked off EGR vac hose, I have some neat smooth tape (used to mask brickwork so sticks to anything and comes off cleanly) so can fit this to seal the pipe and push the hose back over it.

I am coming down on the petrol side myself, mainly as I understand them more. Parts seem cheaper and (avoiding DPF engines) there seems less to confuse me.
This is not a pollution issue as sad to say I think we are looking at environmental repair by reducing car emissions, as they say, disappearing in the rear view mirror.
I don't think they would know if it was not working as they cut in and out depending on temp and rpm ? so if the engine is reasonably ok it would probably pass anyway ?

I can't seem to find info on the NOx emissions at 2500C and what the actual temperature is when the fuel goes bang in the cylinder. If less than 2500C then no problem anyway

Not sure where you're getting this 2500c figure from. It's more like 1300c, and under that NOx is still produced, just in lesser quantities.

http://www.epa.gov/ttncatc1/dir1/fnoxdoc.pdf" onclick="window.open(this.href);return false;

Plenty of info around on google..

Combustion temp is around 550-600c by the looks of things.

It's still an issue. It might not produce that much NOx per vehicle.. but just think how many vehicles there are? That's why it becomes an issue. If it was just you driving around pumping out NOx, then no problem. Over 50% of new cars registered in the UK alone last year were diesels - over a million. The DVLA say , regarding diesel vehicles registered in the UK "Most of these (almost 9.4 million) were diesel cars, accounting for nearly 32.7 per cent of all licensed cars, up from only 7.4 per cent in 1994.

That's why it's an issue and must be controlled.

[charentejohn]

Interesting article, especially the other reduction options being considered in the US. I can't find the 2500C article again so maybe I misread something, always happens trying to find something again.
1300C sounds ok though as should still be less than that, unless they mean the temp when it goes bang, the links in the first post said 1000C on compression. Main problem is no real figures produced so a % of a % sounds good but means little. So an increase of 10% sounds bad but if it is only for 1% of the time it is an overall increase of 0.1%. May be all the extra I will output with the EGR disconnected, with nobody producing figures who knows.

Some good info on levels here http://en.wikipedia.org/wiki/European_e ... _standards" onclick="window.open(this.href);return false; showing how diesel NOx limit has gone down by 2/3 since 2000.
These guys seem sceptical that emissions standards are being met at all, basically fiddling the figures http://www.theicct.org/blogs/staff/labo ... issions-eu" onclick="window.open(this.href);return false;

I will consider putting the EGR back if it runs ok without it for a while as I have had a lot of car problems lately and so don't want to do yet another pointless repair. I still think that this is all just a drop in the ocean but it is important to do what you can. These rules only apply to US and Europe really, if Dave takes the UK out of the EU maybe they can increase pollution limits

[citronut]

but how does all this compare to all the hot air being omitted from the house's of commons, by all the blotted blutacrates