EGR should we all be more concerned

[tonymaroney]

EGR reduction

Hhhmm, that doesn't sound so good any more...I didn't know that the 103kW engine was more prone to issues.
I assume that Vagcom'ing the EGR valve down to a low level also will have a similar effect as putting the staight through pipe in?...ie warning codes get thrown and exhaust temps rise?
I really just don't like the EGR putting all that sludge into the inlet manifold. Some of the photos you see of cars that are about 60K are just incredibly bad. My car blows a hell of a lot of brown particulates out the back (from day one...which may or may not be due to the EGR...more likely the MAF?)...way more than other 103kW TDI's I see. I would hate to know how bad that inlet manifold is after getting excess particulate matter coming back around through the EGR.
I've had the EGR checked and it seems to work, but I am considering replacing it regardless and cleaning as much stuff out of the intake manifold as I can....But other than install a Provent there seems to be no other way to reduce the crud forming via the EGR flow? Correct? (Fuel additives aren't targeting this EGR area, so that's not a solution from what I have read).

A few people have mentioned that the egr valve and intake manifold are very tricky to get off?...what is the main reason for the trickiness? It "looks" easy, but I've been caught out before!

Thanks,
Tony

[Greg Roles]

Tony,

It's a disaster waiting to happen for sure. You can either decide to pull it all apart and clean it out to the best of your ability every 60-80k, but the problem there is how to clean out the black plastic inlet manifold runners, which head downwards after the EGR inlet. These will no doubt block up as well, and any sort of cleaner or residue can become fuel and upon starting you could have a run away situation. I cleaned mine with carb cleaner, let it air for hours, gave it a blow out with the compresser, yet still on starting the next morning it had a bit of a rev. Remember a diesel is throttled by fuel, so putting anything combustable ( including dislodging sludge ) can become like flooring the throttle.

My temporary solution is very illegal and I'm routing the Provent oil vapour into my exhaust. On driving you get a bit of heat into the exhaust and I figure it would burn off, but at idle, when the exhaust temps drop down to below 100 degrees ( amazing hey! ) you can definately smell oil fumes from my exhaust. Not badly so, but no doubt there. I actually turn the car off at the lights most of the time because I'm aware of this and how it may affect others.

I'm about to get the car chipped, and am hoping the tuner can turn off my EGR circuit as my plan is to remove the whole thing and put a plate right up at the exhaust manifold. This is going to raise my exhaust temps, but so too am I going to run a constant boost controlled / EGT controlled water meth system to drop the temps down, so it's going to be a trade off. I have an EGT gauge, and keep an eye on the stock temps, for in the end even if you do hobble your EGR system, all you need do is be aware of the EGT's when you floor it, and just minimise your time above 650-700 degrees C. Gale Banks and Bullydog, some of the major diesel tuners in the USA reckon 1250 -1350 degrees F is about the upper end of safe for any turbo for any sort of longevity.

There have been three 103kw turbo's go pop that I'm aware of, after tunes, but still I think you'd simply have to install a gauge, do all you can to get the inlet charge cool ( Cold Air Inlet, intercooler water spray, heat wrap the inlet ) and just drive to your EGT's.

There's certainly going to be a lot of TDI's having problems from sludge over coming years as they rack up the miles. Good you are thinking ahead!

[bluey]

But if the diesel burns with less soot using higher cetane fuel - either BP Ultimate Diesel or Caltex Vortex Diesel or a cetane improving fuel additive (Moreys Diesel Smoke Killer or similar), doesn't that eliminate or at least reduce the soot clogging problem?????

Note the VW specs for most cars (not Polo) *require* a high cetane fuel.

I also note that the plastic formed rocker cover is designed by Mann and Hummel for VW to catch blow-by gas liquids.

FYI: Article on cleaning carbon from TDI intake systems

[tonymaroney]

Egt

Thanks for the comprehensive response Greg.

You have the 125kW version if I remember correctly so you can fiddle a bit more and tolerate more EG temperature by the sounds of it.

I haven't looked into an EGT guage yet...how involved is the setup, and what parts did you use?

With the EGR valve...when you stomp on the accelerator I thought I read somewhere that it closes the EGR valve? Might be faulty info...but if that is correct then shutting off the EGR altogether may not have "too" much affect on the EGR temp? I actually don't drive the car hard, and only want to do the occasional fast take off etc, but I want to reduce that crud from going into my engine as well. There really does not appear to be an ideal solution to my problem! There's definitely no easy solution thats for sure.

Tony

[Greg Roles]

Bluey I'd recommend everyone planning on keeping any modern diesel past 100k's runs BP ultimate or similar, additives etc, there is simply no better option. You're right in that it may reduce it, but in the end if the car clogs up at 140k vs 100k it's still all bad in my book. The inlet runners are slowly getting smaller, your air flow is steadily reducing, and you'll have to drive the thing harder and harder to get the same power output, plus the max will drop as it clogs. Less air equals more soot, and for the 125kw and 2009 diesels with DPF's that means a quicker permanent clog. All bad news to me!

Yeah I have the 125, and the additional VW designed thermal handling stuff, but there's still going to be the same 1300 degree F ceiling I'm aiming at.

The whole reason behind EGR for the diesel is to reduce combustion temps, which in turn reduces NO emissions. Diesels produce less greenhouse gas, but far more NO which is bad news. Adding exhaust to the inlet charge lowers the O2 available at bang time, and slows the burn, reducing NO output. No other reason they do it. I've no idea exactly how the valve operates, and when, but going by my EGT gauge, only when you're up it does the temp climb anywhere over 400 degrees. In my mind this is when the EGR needs to operate! Either way it's reducing power, and that's what I'm all about.

EGT gauge is easy except for drilling a hole into the exhaust for the sensor. Alternately you could get a scan gauge ala Polar and simply read from the stock EGT probe in the actual manifold, showing true exhaust temps. I'm only seeing post temps, which are apparently 100 degrees or so less than what the turbo actually sees. Drilling into the top of my DPF was a mission, very hard metal, and cutting any sort of thread into it was next to impossible. Still with some liquid metal it's hung in there even when I doubted if it would!

Ideally you'd get a EGT mount ring welded in, and I've got one ready for my forthcoming dump pipe from Gavin on here. Bottom line easiest way would be a scan guage, do a search for Polars one, it reads several sensors which is nice in a compact unit. I wanted choice where I put my sensors, so I have seperate gauges beneath my single DIN aftermarket stereo. see my tinkering begin thread if you're interested there.

Oddly enough all the girlies with no idea point to the gauges and say "I like those..."

Bonus!

[gldgti]

keep in mind that there's no reason (if your getting a custom tune anyway) you cant delete the EGR and have low EGT's - its just a matter of running a little more air. running excess air always reduces the EGT on a diesel - and i've seen this on my own car given i've upped the power significantly yet lowered EGT's just with tuning (running even more boost compared to the extra fuel added).

in the end, running extra air will both reduce the EGT's AND reduce the soot emissions, because it will encourage a more complete burn.

i only make any smoke during a laggy transition now - full throttle is clear as day.

[Greg Roles]

Very good point mate, one facet I hadn't really considered!

[bluey]

keep in mind that there's no reason (if your getting a custom tune anyway) you cant delete the EGR and have low EGT's - its just a matter of running a little more air. [...]

So why doesn't VW just do the more air thing....anyone got any ideas????

[Greg Roles]

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.....

[tonymaroney]

running more air?

Ok I understand most of this but need to clarify a few bits:

By running more air do you mean you get your APR, Oettinger or GIAC ECU flash to actually be individually tuned to run a bit leaner (ie lower Fuel to air ratio) or is it that you dial up more boost and ram more air in there? With the reflash I watched there really was no discussion of extra services like that but I assume you can ask for it at a price.

So my undestanding is that we are looking at three scenarios:
1) Stock...and just to put some numbers in (not accurate, just to compare options 1,2&3) lets say the stock mixture going into the combustion cylinder is:

10ml Diesel
1500ml Ambient Air
500ml of Recirculated exhaust gas from the EGR

this would give us normal operating temps and soot etc.

2) If you remove the EGR valve and put a straight through pipe in (or block it off etc), and a recessed O2 sensor in the exhaust you get:

10ml Diesel (same)
2000ml Ambient Air (changed)

this would give much more O2 for combustion, so better combustion, maybe less soot, and better fuel consumption BUT higher EGT's, possibly cooking the turbo.

3) And lastly if you remove the EGR valve and put a straight through pipe in (or block it off etc) with a recessed O2 sensor in the exhaust BUT ALSO get the car chipped and rebalance the air:fuel ratio (by raising the turbo boost?? Not sure about this bit!):

10ml Diesel (same or it might be slightly less?)
2500ml Ambient Air (changed)

this would give good combustion due to the decent amount of oxygen present, but the heat is drawn away down the exhaust better due to the greater mass flow of air(?).


Is all that correct? To me, if I want to keep the 103kW TDI engine free of EGR oil and soot, but refrain from cooking the turbo I would need to remove the egr, space out the exhaust O2 sensor, and reflash the car and increase the boost pressure? (and install an EGT monitor).
Actually can the ECU change bit for extra boost (or whatever) be done without a reflash? Just via Vagcom?

Sorry for the long post. I am just interested in doing this properly, and preferably without cooking a turbo or two!

Thanks,
Tony

[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

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.