Diesels and EGR

[COcyclist]

Thanks guys for all your responses. I am trying to make the best informed decision and I appreciate all your viewpoints. Nacht, environmental concerns are one of my considerations. (most days I do not start my car and commute by bicycle even down to 20 below zero). On the other hand, I live in a sparsely populated area surrounded by three coal fired power plants. My NOx contribution would be minimal from a 50 mpg vehicle that I barely drive.

VWs are prone to manifold clogging ($300 repair- the manifold must be removed or replaced), cracked EGR tubes (I'm on my second set- $300 in parts alone), clogged EGR coolers, and sticking/clogged EGR valves making the vehicle run poorly.

My original post was to ask how it affects primarily highway mpg? Keep those comments on efficiency coming!

[UFO]

Originally Posted by Gasoline Fumes

It wasn't long ago that I cleaned it and he had it cleaned by somebody else a couple of years before that. He's running WVO most of the time too. Still gets clogged with a black sooty tar. It's a 1999.5 TDI. The other one with the EGR disabled is a 2002 TDI running on diesel only.

That WVO 99.5 TDI must have a lot of blow-by.

[dremd]

Originally Posted by UFO

When I ran with disabled EGR in my TDI (with CEL set) it made no significant difference in economy. However it made a huge improvement (about 10%!) in the fuel economy of my Jeep CRD, and that has a modification that tricks the ECU so it doesn't set a CEL.

So I am working on the same device for my TDI and will document any differences here when I do that.

just change the vag com adaption block 3 to 33768 it turns the duty cycle to near 0, and causes no CEL at least on ALH cars.

I run my egr at stock, I see a .75-1 psi increase of boost at 75 mph with it off and would prefer to keep NOX down.

[UFO]

Vag Com is a bit out of my price range. I can build a circuit for half, and perhaps sell the extra to come out ahead. Maybe then I can get Vag Com in time to do my timing belt this spring.

[bestclimb]

That is assuming of course that your diesel has a catalytic system of some sort, many diesels don't.

[dremd]

Originally Posted by UFO

Vag Com is a bit out of my price range. I can build a circuit for half, and perhaps sell the extra to come out ahead. Maybe then I can get Vag Com in time to do my timing belt this spring.

I'd try and borrow one if that was the case.
There are a few locators listed at New VAG-Com Locator website - TDIClub Forums

[mnmarcus]

"They put cats on diesels now?
What next, spraying pee pee into the exhaust?"

This has to be a sarcastic comment (and you've heard of AdBlue), please respond as I can't believe this is a incredible coincidence?



"What Does AdBlue Do?
Used in conjunction with a Selective Catalytic Reduction (SCR) converter, AdBlue has a profound effect on otherwise difficult to control oxides of nitrogen (NOx) diesel emissions. On average, NOx emissions are reduced on the order of approximately 80 percent. The AdBlue solution is comprised of 32.5 percent high purity urea diluted in distilled water and carried onboard the diesel vehicle in a special independent tank. Under the direction of the onboard computer and an NOx sensor, the fluid is pumped into the exhaust stream at the rate of 2 to 4 ounces to a gallon of ultra low sulfur diesel fuel (ULSD) consumed. And it is here, in the hot exhaust stack, where the urea solution is converted into ammonia (NH3) which reacts with NOx in the exhaust. The resulting chemical break down and re-bonding of the constituent elements of each reactant produces plain nitrogen and water vapor."

[COcyclist]

Originally Posted by Big Dave

It varies from engine to engine.

Doesn't seem to help VW TDI engines.

It helps Ford 6.0 and 6.4 engines a lot as it does the Cummins 24 valve.

Big Dave, If I am reading this correctly, EGR HELPS with mpg in some diesels but hurts the VW TDI? Can you add links to your sources please? Some folks claim EGR hurts mileage, some say no difference, and some say it helps diesel mpg.

[UFO]

My running assumption is it's the quantity of EGR. The CRD has a huge EGR flow, and that much EGR is reducing the thermal efficiency of the engine by reducing the combustion temperature. My contention is all EGR systems will reduce mileage, and the greater amount of flow makes it more obvious.

[Duffman]

Originally Posted by COcyclist

Big Dave, If I am reading this correctly, EGR HELPS with mpg in some diesels but hurts the VW TDI? Can you add links to your sources please? Some folks claim EGR hurts mileage, some say no difference, and some say it helps diesel mpg.

Pulling the EGR cable throws a code on some vehicles. This puts them into a limp mode which adjusts injection timing, messes with the VGT boost tables etc. Less EGR is better for economy but it may be offset by the computer depending on the vehicle.