EGR should we all be more concerned

[gldgti]

right - well you demand answers... so to be brutally honest - not really.

yes - i was insinuating you get a reflash that tells the turbo to run higher boost everywhere it can (or conversely a bit less fuel for the boost/airflow it is taking in) if possible.

in any case where the air:fuel ratio is leaner than before, exhaust temps will be lower, regardless of EGR.

you cannot infer air:fuel ratio numbers with volume measurelents like ml - we are always talking in terms of mass. by the ideal gas law, if we know volume flow rate and temperature, we should be able to calculate mass OK.

as to the actual ratios - i wouldnt suppose to suggest numbers here - thats a problem best solved by someone with a car, a dyno and a bunch of logging equipment. however, the chemistry says that more air will give you lower EGT's - in general terms, this is what you aim for. unfortunately for you, you have an ECU telling your fuel injection system how much fuel to inject and it tries to keep to a ratio set by the factory that is worked out as a best compromise for power, economy, longevity of components and emissions. by changing anything in the system, you are really demanding a new set of rules.

I would say with certainty that the optimum air:fuel ratio set by the factory for a stock vehicle is quite different from the optimum setup for a vehicle that has no EGR, and consequently the user wishes to run leaner to reduce EGT's and also to clean up the exhaust in a more direct manner.

running excess air is not hte optimum tune for power. its reasonably well understood that diesels at the end of the day make the most torque per unit fuel injected running barely past the smoke limit. so if you arent smoking a little, you arent making as much power as you can. that's not to say you cant afford to take a little hit there to clean up the exhaust however - and in extreme applications, we see some tuners running diesels both at the smoke limit and others running lean. its a matter of preference... but at the utmost extreme, you are putting more stress on the engine and turbocharger if you are pumping more air in than you need to to make the power you want. if you are a long way from the limits of the engine, this is OK. if you are drag racing, maybe you wont care about hte smoke. see my point?

[gldgti]

Everything is a trade off.....

exactly.

for some of us, trying things out is most of hte fun. if you actually worried about damaging your engine, and what it will cost you - dont change a thing

(apart from getting a pro-vent)

[tonymaroney]

Thanks for the response. Despite my poor attempt to explain what I was on about, your answers are what I was after!
Don't worry...I'm a car fiddler from way back (MGB mkI resto etc) but I have ZERO experience with turbos. My basic issue with all of this is the fact that burnt waste coming out of the cylinders is getting put back into the cylinders, and the pipework is getting badly fouled in the process. I know that VW had to do it to pass the smog testing stuff, but come on!! That's just a nasty thing to do to an engine.
I might go for the fiddling option later on, but at the moment I will manually clean what I can, replace a suspect egr valve (with a new one) and then strongly consider a Provent.
Thanks again,
Tony

[bluey]

Because "more air" involves pushing the turbo harder, and then you run into other problems like efficiency and the far worse "surge" where the impeller basically cavitates. Everything is a trade off.....

Interesting that the US Underhood Service article on TDI carbon cleaning says its OK to have up to 10mm of carbon deposit!

It looks like the photos from the article are missing at present. I saved a copy a while back:

[Greg Roles]

Tony,

I'm not sure about the EGR, but poor old Hi Torque on here had to have his throttle flap mechanism replaced due to crud buildup on his TDI, and it was a $1k part from memory!! No doubt the EGR will be pricey too, have a talk to Transporter, he has some good links to wreckers overseas where VAG parts are far more reasonable prices. I suspect if you clean your EGR valve out it'll be able to work fine, it's probably gunked up.

I've yet to pull mine all the way off, but I hear it's the screw inside the assembly that is the problem. I'll be finding out over Christmas hopefully!

Personally I'd use the money to get a Provent, for even though you're still getting exhaust, less oil vapour will decrease the sludge build up and that can only be good!

Here's the info from my 125kw self study module pulled from Erwin. To my knowledge the only difference to the 103kw is the exhaust gas cooler is bigger on the 125kw, part of the thermal handling upgrades I was mentioning.

[Greg Roles]

[Greg Roles]

Oh and I've simply pulled the plug on the valve to see what happened, and it threw up an error code, but the car felt a bit gutless, so it obviously went onto some sort of power limiting safety map. Had to reset it all via Vag Com.

[gldgti]

not exactly what you want to hear is it?

it really seems that the biggest obstacle for diesels is nitrous oxide output - has been the case for a long time now. just think, if it werent for the nitrous emissions, the factory setup would likely come without a DPF, EGR, or anyhting like that. just run excess air.

back in the day when the mk1 diesel golf came out with the 50hp 1.5l engine (and 1.6, and 1.6TD) they were EXEMPT from the nitrous emissions test because they performed so well in all the other emissions tests (unburned hydrocarbons, CO2 (good fuel efficiency), CO, etc.

they figured back then that if the car could get 4.7l/100km around town and 5.5l/100km on the hiway, it was automotically good for the environment....i would generally agree.

[gldgti]

not exactly what you want to hear is it?

it really seems that the biggest obstacle for diesels is nitrous oxide output - has been the case for a long time now. just think, if it werent for the nitrous emissions, the factory setup would likely come without a DPF, EGR, or anyhting like that. just run excess air.

back in the day when the mk1 diesel golf came out with the 50hp 1.5l engine (and 1.6, and 1.6TD) they were EXEMPT from the nitrous emissions test because they performed so well in all the other emissions tests (unburned hydrocarbons, CO2 (good fuel efficiency), CO, etc.

they figured back then that if the car could get 4.7l/100km around town and 5.5l/100km on the hiway, it was automotically good for the environment....i would generally agree.

the biggie is injection timing - advanced injection created very intense peaks in cylinder presure and this is when the NOx is produced. on pump diesel, you can combat this by running injection timing a little retarded but at the expense of allowing other emissions to increase a little. on ester based fuels (Bio D) the higher oxygen content of the fuel allows for retarded injection timing without worsening other emissions in some cases - so depending on hte study you read, you might be able to decrease the nitrous emissions by running bio-diesel and retarded timing.

multi-stage injection goes a way towards improving this i believe, but with direct injection diesels there is no mechanical barrier to prevent the high peak cylinder pressures apart from the multi stage injection or running poor combustion (EGR). the old indirect injection prechamber diesels allow for a smoother more controlled flame fornt propagation, since the diesel is injected and combusts over a long period of time with respect to piston travel and must expand out into the cylinder through the pre-chamber port. not ideal for making big torque (all the IDI's make less torque at low rpm compared with the TDI's) but better for emissions in this case.

this site has some text extracts on the subject:
http://www.journeytoforever.org/biodiesel_nox.html

[tonymaroney]

Greg you mentioned that you might look into the EGR system over xmas...are you going to pull off the intake manifold? (in my diagram they call it the intake pipe...number 5 on your picture). I am just wondering if it would be possible to unbolt the intake manifold, egr intake pipe etc and the big rubber air feed pipe at the bottom and lift the whole manifold+egr valve+flap motor out in one go? The gasket for the intake manifold looks expensive! Where do you get your gaskets and O-rings from in Brisbane?
Also I am looking at one day getting a Vagcom-USB cable etc...if you have one where did you get yours and how much did it cost?

I have come to the distinct conclusion that I have babied my motor too much and inadvertently may have gummed it up...first stage I think will be to just clean it all up as best as possible, then I'll stick to good fuel. A Provent might be on the cards if I go to all the effort of cleaning the system up. And I might consider a Bluefin ecu flash too (for fun!), but those EGT temps are a worry. Electronic EGT monitoring doesn't look as easy/cheap as I'd hoped so I'm not so sure I can do that...I might just have to be mindful of the EGT temp and not go too crazy for too long a period!
Thanks again for the helpful posts above!
Tony