Blocking EGR keeps oil clean - how?

[joeker]

I keep hearing that blocking the EGR will help keep my oil clean. For example, I copied the following quote from a dissertation on NADS:

Blocking hte EGR not only helps to keep your inlet manifold and oil clean

From my understanding, the EGR just adds exhaust gases into the inlet in an attempt to keep emissions lower. Anything in the exhaust gases would have been through the engine once and burned (lar4gely anyway) and will now be circulated through the engine again and out the exhaust.

How does stopping that happening keep my oil cleaner?

This may be a stupid question, but it is seriously meant - I just don't know, so be gentle with your replies.

[04OFF]

basically, Small deposits from the combustion process, always find their way past the piston rings during normal engine usage, these deposits build up over time and can add to contamination of the oil.

Exhaust gas is a "waste" product, this is designed to be expelled from the engine, recycling the waste back through the engine would increase deposits, and therefore dirty your oil faster.

[joeker]

basically, Small deposits from the combustion process, always find their way past the piston rings during normal engine usage, these deposits build up over time and can add to contamination of the oil.

Exhaust gas is a "waste" product, this is designed to be expelled from the engine, recycling the waste back through the engine would increase deposits, and therefore dirty your oil faster.

So it is just the soot from the exhaust that is being recycled and some part of it blows by and into the oil.

That's weird really, and I still don't understand how it works.

If a normal cyclinder charge (ie with no EGR) is burned then you get exhaust gases with a measure of soot and that blows out the back. Let's say (for the sake of easy calculation) that it produces 10g of soot. Some of that gets blown into the oil through blowby, let's say 1g makes its way past the rings.

I don't know what proportion of the cylinder fill is recycled exhaust gas, but I can't imagine it is much, but if we say that it is 10%, again for the ease of calculation. Now the gas is inert, but the soot it contains (10% of 10g is 1g) will actually burn in the cylinder - that's how a diesel particulate filter gets cleaned, by burning the soot - so that soot will dramatically reduce in content. Let's say it all gets burned.

So now we have a cylinder that has a reduced charge (remember 10% of the cylinder fill is now EGR) so instead of the full 10g of soot it will only be able to produce 9g of soot. The soot in the EGR gets burned so the exhaust gas now exiting the engine has 9g of soot in it. That would mean that the blowby would also have less soot in it.

So how does blocking an EGR actually keep the oil cleaner? I really don't understand. Where is my picture of how things work missing a piece?

FWIW, I have the catch can to reduce the oil mist cycling through the system and the EGR blocked and the Dawes valve etc etc.

[04OFF]

I think your reading too much into it, its part of the whole NADS thing, its a combination of mods to aid your engine.

Blocking the EGR is only part of the package, by itself may not make any noticeable difference to the colour of your oil, but its still returning a waste product (exhaust) to your engines insides, your engine does not need or want it , and over time as you engine ages, it may add to problems


I don't think you'l find the EGR valve has even close to a "exact" measure of exhaust entering the cylinders, theres only so much room in the combustion chamber, so you add some exhaust, somethings gotta give, its your air/fuel ratio, a varying air/fuel ratio may lead to further deposits for many resons.




Think of it like eating a little bit of your own poo to save polution, sure, a little bit won't hurt, but over time as you get older, don't be surprised if it leads to problems

[mudski]

In a nutshell. Part 1. Your engine sucks in clean air and mixes it with fuel and then it goes into the combustion chamber, gets burnt, some of the soot from the burnt fuel sticks to the cylinder walls and gets mixed into the engine oil.
Part 2, Your engine sucks in clean air ALSO with used exhaust via the EGR, mixes it with the fuel and then it goes into the combustion chamber, gets burnt, and now more soot from the burnt fuel (because of the already dirty air being sucked in) will stick to the cylinder walls and mix with the oil.
So if you block the EGR, you get clean air on every combustion process, not dirty air.
Cheers.

[joeker]

Thanks guys.

I have the NADS so I have no way that I want to go back and test this out, it is just that it didn't quite make sense to me as far as keeping oil clean. However, I think I will just let it go at that.

Sometimes the world just doesn't make sense does it?

[taslucas]

Thanks guys.

I have the NADS so I have no way that I want to go back and test this out, it is just that it didn't quite make sense to me as far as keeping oil clean. However, I think I will just let it go at that.

Sometimes the world just doesn't make sense does it?

It does if you read mudski's post:-)

[joeker]

Just had a bit of work done as the Troll was whistling, especially when cold. Turned out to be a warped exhaust manifold. i took it into the diesel injection and turbocharging specialists in Darwin - MTQ.

While paying the $3,020 bill (things like the belt tensioner were stuffed too - $525 to replace! etc etc and the exhaust manifold gasket was $250 plus various other gaskets nearly $100 plus new bolts for everything about $270) i discussed the various NADS components with him and got his opinion. Presumably a highly educated one.

1) Oil catch can - useful thing to have but make sure the hoses are wide enough.
2) Dawes valve - Why bother? The computer takes care of it for you. Eventually he agreed that it was a reasonable safety device for those occasions where the computer gets corrupted data feeds from things like dirty MAFs.
3) Needle valve - Umm, yeah, maybe. The boost curve looks smoother but really, why bother? Just something else to be maladjusted or break.
4) Pyro gauges Not needed unless you do something else. If you fit a chip then you take things outside of the normal range and a pyro could be useful. Otherwise a waste of time.
5) Boost gauge. Not needed if you have the Dawes valve. If underboosting you can tell from the seat of your pants.
6) EGR blocking. He couldn't recommend it as it is not a legal thing to do. However, if it is done he can see benefits in keeping a clean fuel/air mixture.

Worth thinking about some of those points isn't it, but we all still like to play with things.

[stock patrol]

Hi All; I have done some but not all NADS as money don't grow on tree in my yard. Did chip years ago ( no problems ) yet. Beaudesert 2 3/4 exhaust last year. This year snorkel. Currently on trip to Alice Spring and troll going excellent.

Just had a bit of work done as the Troll was whistling, especially when cold. Turned out to be a warped exhaust manifold. i took it into the diesel injection and turbocharging specialists in Darwin - MTQ.

While paying the $3,020 bill (things like the belt tensioner were stuffed too - $525 to replace! etc etc and the exhaust manifold gasket was $250 plus various other gaskets nearly $100 plus new bolts for everything about $270) i discussed the various NADS components with him and got his opinion. Presumably a highly educated one.

1) Oil catch can - useful thing to have but make sure the hoses are wide enough.
2) Dawes valve - Why bother? The computer takes care of it for you. Eventually he agreed that it was a reasonable safety device for those occasions where the computer gets corrupted data feeds from things like dirty MAFs.
3) Needle valve - Umm, yeah, maybe. The boost curve looks smoother but really, why bother? Just something else to be maladjusted or break.
4) Pyro gauges Not needed unless you do something else. If you fit a chip then you take things outside of the normal range and a pyro could be useful. Otherwise a waste of time.
5) Boost gauge. Not needed if you have the Dawes valve. If underboosting you can tell from the seat of your pants.
6) EGR blocking. He couldn't recommend it as it is not a legal thing to do. However, if it is done he can see benefits in keeping a clean fuel/air mixture.

Worth thinking about some of those points isn't it, but we all still like to play with things.

[joeker]

It does if you read mudski's post:-)

Does it really make sense though?

After all, if the reason the oil gets dirty is because there is more soot in the combustion chamber then there will be more soot blowing out the exhaust.

Therefore, if there is more soot blowing out the exhaust there will be more soot coming in the EGR and therefore EVEN MORE soot in the combustion chamber and blowing out the exhaust which, in a vicious cycle will produce even more soot in and out again.

If the theory is correct then we'll end up with a big soot influx each intake stroke.

Of course, the EGR is not open all the time and there will be a point where the small volume of sooty exhaust gas coming in will balance out with the fresh air intake and i suppose that is the crux of it all.

Thanks for your forbearance guys - perhaps it does make sense after all.