EGR myths and cold starts.
 

Many Volvo diesels are fitted with EGR valves designed to cut Nox emissions that are real health risk factors. The engines ECU warm up program is designed with the EGR functioning, if it fails or some twit deletes it (New MOT failure point), the engine takes longer to warm up and it is the period the mixture is richer than normal that causes the most in cylinder deposits. If the engine was designed with an EGR present they do not increase wear rates but reduce them!

The difference in fuel consumption is minimal unless it blocks, as it will often result in a faster warm up time, even if there is a loss of a few percent when warm. Tiny Carbon particles recirculated by an EGR are very soft in comparison with cylinder head components, and they make no difference to ring or valve guides (Tiny sand particles are a very different story). If the cylinder walls or valve seats are pitted from corrosion (Use of high Sulphur fuel or simple lack of use), they even help by filling in the tiny crevices.

For a diesel in good condition, the EGR often only needs cleaning every cam belt service (Mine has not been done for nearly 100K km, although the intake was cleaned out and a new O ring used). I've looked at a lot of different used oil analysis results for diesels that suffer multiple stop starts and time at idle, that tends to foul up the exhaust system more than normal. The ones where the owner deletes the EGR, show a spike in both Iron, Aluminium and Chrome from the top end, although it's not much of factor with big rigs that use a full pre heat system.

Letting the EGR block up is also bad news, but all it seems to do in oil terms is increase the insolubles figure slightly, from increased blowby.
If you want to keep an EGR clean, just use top quality fuel (Or DYOR on good fuel additives) and try to get some motorway time every month to burn out the cold start deposits. Using a direct feed purge to clean the injectors of gum and using a major brand full synthetic that contains a lot of detergent additives will help keep the rings clean, as compression is also a factor in Carbon deposit terms. Shell Ultra, or LM Synthoils are both better cleaners than Castrol Edge, as they use far better base stocks that are natural solvents. Mobil 1 HC synthetics also clean well.

Oddly enough if you want to improve the main block life of a diesel, one real good extra is a simple stick on sump pan oil heater. The cost of the electricity might be the same as the fuel saved, but they are real good news, because about half of all main block wear occurs when an engine is first cold started. If you dodge cold starts by heating the oil (Full block heaters are better, but more expensive and can be difficult to install), it can easily half the warm up time and get the heater working faster, which is great for the toes.
Such pre heaters can increase the main block, battery and alternator life by around one quarter if used on a daily basis and are fitted as standard (Full block heaters) to many emergency call out vehicles in Germany, doctors cars in particular, like one top of the range Audi near me, that is parked on the pavement when the owner is on call and kept fully warmed up including cabin heat, so the doctor can just floor it immediately and let the traction control deal with the consequences.
He did admit to killing the neighbours cat last winter, which understood less about cold starts than the average boy racer. Poor thing thought it had found a warm dry spot to sleep and finished up with Conti winter tyre tread marks instead!

PS: There are a lot of confusing EGR related junk articles around, partly because of early model EGR systems that did not work too well and companies selling related parts, but as far as I am aware all Volvo engines were designed with EGR units in mind, whereas some older GM and Crysler engines were not, even a few early VW diesels ran into some issues with valves blocking faster than expected.
I just look at facts not press or biased articles and I've seen enough UOA results of before and after deletes to know it's bad news to fiddle with what the Volvo Gods designed.
The data I've seen for pre heat use is for trucks only so far, but I will try and get some figures for my own diesel (Wolverine 250W pad) this winter, because the 25% improvement for Canadian trucks and German diesel cars might be effected by the use of GTL or G4 group synthetics that were not used by those vehicles.

(Copy ZF/MTU English tech forum file)

AA legal opinion about deletes copy.
 

I underestimated the legal situation in the UK as regards deleted or gutted EGR, CAT or DPF's. This is from the AA site:

According to the Department for Transport, it is an offence under the Road vehicles (Construction and Use) Regulations (Regulation 61a(3)) to use a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. Removal of a DPF will almost invariably contravene these requirements, making the vehicle illegal for road use.

That same regulations covers the EGR and CAT, so I presume it is in fact a Police matter, rather than just a post crash insurance or MOT matter.
Breach of such a regulation is an almost certain cop out for an insurance company, as it's an intentional act. That means the policy is not valid both for the regulation above and the gross negligence clause.

PS: The UK Police are too busy for such matters, but the insurance industry are not, so I doubt if it will get mentioned in any policy wording, as to use a Dell Boy saying, "It's another nice little earner", to have some Nox and Carbon sniffing fan insure their car, but not get paid for any accidents regardless of who was to blame and even subject to a law suit from their very own insurer for 3rd party pay outs they have to pay.

OFF TOPIC DPF RANT:
I do feel sorry for DPF sufferers as the idea was a good one, but it got pushed through and into production far too quickly and even clashed directly with decisions taken with regards to increasing fuel economy and problems VW were having over cheap top end steel quality that got them into trouble with CAT related engine oil restrictions.
Then add in the fact that the dealers did not want to use real expensive engine oil that can cope with fuel contamination more effectively and the result has been a fiasco!

There is no point trying to use extra Zinc additives if you have a DPF, as they can help block both the CAT and DPF, so you get stuck with a low ash (Low Zinc) oil that is real bad news in block wear rate terms. Some far Eastern car companies panicked and boosted the amount of Moly (Cheap stuff not the real MoS2 made in Germany) to nearly 10 times the pre DPF level (Honda, Nissan etc), whilst ignoring the obvious side effect of too much Moly, which is long term corrosion. A classic case of swapping one in warranty problem for another post warranty one.

The Germans know the answer to most oily questions, so they simply ignored VW, Ford and other approved oil requirements for DPF diesels and asked the Iffy lube gang to forget about fuel economy for a while and move up from x/30 to x/40's and start selling LM Ceratec to bad cases of fuel contamination. VW kept fairly silent about funding the R&D required for the Ceramic particles involved, as they could not change their approved oils list and no oil company is producing an oil with it in at present anyway.

My eyes hurt now!

Serious? the mixture is richer during warmup (without egr) in diesels ?
Its the other way arround
Without egr the air to fuel ratio is (way)higher wich means leaner and hotter wich creates the nox in the first place :heat!


The purpose of egr is to cool combustion down (and replace the part of oxygen & nitrogen with an inert (exhaust)gas that isnt needed for combustion (in part engineload) with fuel but can react due to heat with eachother ) in part engineload to prevent nox from forming

The reason the engine warms up faster in modern diesels with egr has nothing to do with the (cooler) Combustion itsself but with the mandatory egrcoolers wich extract egr heat directly from the exhaustgasses into the coolant

So blocking the egr means also no hot exhaustflow trough the egrcooler and no extra heat into the coolant

One reason that wearrates could go down with a diesel with egr compared to a blocked one can be to the fact that more carbon particulates dissolved in oil can act if they are squashed in the engine as a "graphite" (not so much to the point the oil cant suspend it anymore ofcourse)

ps

Air to fuel ratios in diesels have completely different meanings compared to (indirect injected)gasoline engines (the only engines wich use fuelenrichment during warmup) , if nox played no role diesels were running extremely lean as in the old days in part load 60 to 1 also during warmup
The reason a gasoline engine runs rich during warmup has nothing to do with emmissions but is required to let the engine run in the first place because too much fuel will condens on cold cilinder walls wich prevent proper combustion and needs to be compensated for with extra fuel to leave enough gasoline in gasform to combust with lamda 1
Thats why direct injection gasoline engines dont need fuel enrichment anymore because the fuel is injected at the end of compression almost like a diesel and cant condens at the cilinder walls
In dieselengines egr increases fuelconsumption but egr in gasoline engines decreases fuelconsumption because in part load the partly closed throtlle will create underpressure/pumpinglosses wich the egrflow behind the throtlle will equelize

If you read my post again you will see I did not say richer, it just takes longer for the engine to warm up if the EGR is deleted, so the mixture stays in rich burn for longer if the EGR is not functioning.

I agree with the rest of the last post, although Carbon loading of the oil does not matter for a diesel if the oil filter is functioning and the oil is changed before it turns acidic. It does that when the total base number (A direct measure of the amount of active detergents left in the oil) is below the total acids number, which is the game over point for the detergent/dispersant additives in the oil, so any new blowby Carbon will start to form clumps that will cause long term sludge formation in the sump. Before that cross over point (If you don't know the TAN of the used oil, then it will occur when the TBN is below one third of the new oil figure, which is around 3 for most good oils, but gets serious below the 1 min figure quoted by most oil labs).

Oddly enough I've not heard of anyone deleting a petrol engine EGR before, probably because they stay clean for a very long time, whereas a diesel with bad compression or bad injection based in a city can dirty them up a lot faster.

Not only you said that the mixture is richer with functioning egr (in warmup)

You say it again :D

Quicker warm up and decreased efficiency do not need to go hand in hand with egr. Unfortunately this is what egr was designed for though. If egr would only work during warm up would be the ideal situation.

HOWEVER OP presents the claim that egr speed warm up, but what data is this based on? A couple of questions arise: it is typical to cover the front cooling intakes completely here during the winter. You could say this speeds up the warming 2000% or indefinitely, with or without egr since diesels without built-in radiator shutter flaps never reach normal working temperatures in cold conditions. Thus what effect does the egr have?

Egr coolers/heatexchangers transfer (extra)exhaustgas heat into the coolant if in use ,so it warms up faster and in the case of very cold climate it will raise the temp somewhat if the temp is below workingtemp (at workingtemp it wont raise beyond because the thermostat will let it flow away trough the radiator
The problem in (very) cold climates with modern efficient diesels is that there is less heat availible to warm up the engine compared to old diesels and also the cabinheater will extract alot more heat extra ontop of that

940 tdi auto 1995 tdi
 

my engine has this EGR valve its early technology on this engine ,whats your opinion on this on a 1995 vw d24 ?

I dont know this engine in particular ,but most early egr systems had no coolers
So disabling them has no effect on the warmuptime