EGR the story.






From various sources.






Why is it used. To reduce tailpipe emission standards starting with Euro 1 of 1993 to Euro V1 of last year. Main target is Nitrogen Oxide or Nox which is a greenhouse gas.
New cars require them to be fitted to pass Euro emissions and be sold in Europe.


Nox is produced when Nitrogen and Oxygen combine under high temperatures and pressures. So you guessed it the cylinder provides this.


So as the exhaust gas has the oxygen spent in it, introducing some of it into the cylinder reduces the temperatures in the cylinder. Take above and this and it seems logical.


But side effects are bound to happen, yes, less oxygen less power. So under full power conditions the EGR closes and Nox is created.


Then there is a statement, recirculating exhaust gas back into cylinder benefits fuel consumption. This is disputed on this forum. They get this by saying under low load conditions the engines pistons encounter less resistance by having cylinder filled with exhaust gasses. I would think there would be an improper burn here and black smoke due to less oxygen.


They say the removal of an EGR valve will compromise the other parts in the system like the Turbo. But looking back EGR is closed when Turbo is singing under power.


Some engines cope better with a blanking plate but they say the higher exhaust gas temperatures may cause problems, like shortening turbo life and more strain on pistons, valves, lubrication and cooling.


As to blanking there is a mention of a small hole made in the plate to prevent engine run problems or engine light.


As said by another gent on forum, some cars need ECU reprogramming to trick system into thinking EGR is working. But CRD engine has only a Vacuum operated EGR so no electrical's inside it to send signal back to ECU. Or has it wires going inside like the electrical variety that tell ECU that valve is open or closed or giving dash light to say its stuck on its travel.


Removal or blanking of EGR may still let engine pass MOT as Nox is not measured.


But it is illegal under Regulation 61A but there have been no enforcements. May be in future MOT's though. It is a modification under Insurers though.


Good luck, I wouldn't say any think against it.






















































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I've blanked all but my GV since the earliest diesel about the middle 80's which was a year old CX Turbo-D 2.5 and all have given benefits when blanked. The benefits claims such as they are of an EGR are not to do with the car, its performance or its MPG. Now I'm prepared to reconsider it may be true of 2013/14/15 and modern engines and software but not of our generation of vehicles. Its an easy test, measure then blank then measure but make the measuring fair. They don't tell you the EGR costs more money than even the usual in the cold and that the EGR is not needed when you are at motorway revs or that NOx itself is only cleaned @ around 1400°C hence the reason they pump in your exhaust waste, I'm not sure these cold lumps get anywhere near 2500F.

How they behave with petrol I've no idea and I'll reconsider [only] very modern diesel engine design but for me there are no benefits and lots of problems associated with the EGR on our range of CRD's. It's an easy test.

 

big fan of blanking off EGR's. they were created to fulfil a paperwork target and not benefit under real life conditions.

As for the ECU, while it doesn't monitor the EGR directly (though the solenoid coil is usually monitored for shorts or o/c's) It is monitors by the fact that the ECU knows what amount of air the engine needs at every point, some of this comes via the MAF and some via the EGR, if the MAF reading varies by the amount that should be coming from the EGR then it infers that the EGR has failed.....hope this makes sense as I've just got in from a bugger of a night shift and can hardly focus my eyes!!

Regards
Richard

 

I know what you are referring to in a way Richard, I think.
With the EGR blanked the ECU via MAF readings must be having to alter the fueling or boost pressure to keep system in power trim.
The thing that interests me, like in the tuning exhaust pipe principals for power engines, measured pipes/headers, etc. The air boost is at a pressure around 7psi so for the exhaust gases to enter inlet manifold it must be higher. So this shows the back pressure that's in the exhaust just out of the turbo.
Then you get to head scratching mod, back pressure is getting reduced as its going up EGR valve into inlet manifold. Engine needs back pressure so is power reduced here...Need to look further into this issue.

 

Thank you Goggs for your discussion on the EGR valve. Most informative. May I add...

The exhaust gas recycling idea itself came out in the US in the 1960s, as in places like the big californian cities, people got sick of the brown fug (NOX) in the air from all the huge-engined heavyweight cars in use. They were of course all petrol. This can be read up in the SAE papers available in book form which I read avidly in the 1970s.
It is claimed that excessive NOX can cause headaches, but there is no actual definitive proof that I can discover for this. NOX is not a problem in most cities as it is usually just blown away by the weather. But in cities like Los Angeles and Athens, due to the lie of the land etc., this NOX can just hang there, the air getting browner and browner. As Qinteq says, it's never been much of a problem in UK.

NOX is generated by the engine, diesel or petrol, but esp. diesel due to it's very high compression ratio, plus the effect of a turbocharger ramming the air in, thusly increasing the compression and therefore temperature effect. If the turbo is not really doing much due to power demand being low, and therefore exhaust gas speed being low, there will be less NOX. Whether NOX is generated or not depends on the actual combustion temperature, EGR being one way to reduce this temp., the other being to reduce the engine's compression ratio to 16:1 instead of the more efficient 18:1. BUT, this leads to another problem. Reducing the compression ratio to 16:1 INCREASES soot emission, or "particulates" to use the fancy word. So then it's necessary to have a soot-catcher in the exhaust system, the DPF filter as it's called.

All this interference with efficient combustion makes the diesel engine noticeably less good, and INCREASES another emitted nasty, carbon dioxide. Thusly contributing to global warming, along with speed bumps to slow the traffic so it has to speed up again and waste fuel, which goes as CO2 into the air. Another little nasty is having to throttle the diesel engine to reduce NOX, unecessary from an efficiency point of view. Throttling will reduce diesel efficiency as it does petrol, excepting the effect will be less with diesel as the engine always has excess air and is never stoichometric unless some smoke is being emitted. This would be invisible anyhow.

Personally, I think diesel smoke is a more important health-hazard than a little NOX, esp. if the NOX disperses rapidly. Any soot particles will be laced with unburnt hydrocarbons (otherwise there wouldn't be any soot!) which are oily and nasty to breathe into one's lungs.
Speaking from a moral standpoint, not a legal one, I think the law-maker's concentration on NOX is misplaced if it makes diesel engines produce more soot, and pollute the air with more CO2 than is necessary, due to inefficient DPF filters and less efficient engines with EGRs and lowered compression ratios.

Really, all this is a matter of balance, I think the powers that be don't have the balance quite right, perhaps a little fine tuning is needed here.

Leedsman.

 

Leedsman...Leedsman....Shhhhhhh.....Someone in Government ideas section I'm sure will be getting a big bonus with his Idea....Lets put a tax, wait, more tax on Diesel Fuel...They will be printing your words onto a big banner shouting...Public are aware....

 

The likelihood of a Gov. minister reading my writings here is about as likely as me getting my mojo back...
Mind you, if they offered me a job, I'd sure think about it.

Leedsman.

 

A Yorkshire-man never loses his Mojo, I lost two pension funds to Gordon Brown, a fortune in tax back claims to HMRC, three houses and four wives in my travels from Clement Attlee & Winston Churchill to whoever is elected tonight - but I still have not lost my Mojo.

 

Bit of interest here from Car Mechanics mag:
Again they say EGR systems in diesels are good for economy.
Then goes on to the subject of blanking of the EGR to gain power. Like already mentioned people blank of the EGR to gain power but EGR is closed anyway when you give it welly.
The interest here is if the EGR is blanked off the MAF sensor requests more air to pass through it since the extra normally supplied by the EGR is missing. Hence a fault "air mass to high" may come up in fault codes.
This fault was answered when a guys car had this fault and was repaired by renewing the EGR which obviously wasn't working correctly, I take it not opening.
So do we get this fault up with blanked off EGR's on the CRD.