EGR delete a bad idea?

[Rattlenbang]

It occurred to me today: the whole purpose of EGR is to reduce cylinder combustion temperatures, ostensibly to prevent NOx formation. Deleting EGR is a common mod for the L300. I'm wondering if a consequence of that is the higher temperatures that we see damaging heads? After spending a lot of time and money replacing this cracked head, I'm wondering if it wouldn't be smartest to restore that function. Has anyone ever considered this?

[impalator]

My cylinderhead had cracked with EGR open... Nothing blanked off... When I finally blanked it after getting a new head installed, it went better, faster and appeared to not go anywhere near the temps prior (but I also put a bigger diameter, shorter and less restrictive exhaust on and put a new rad, water pump) in as well...

[Mr. Flibble]

I doubt it. Lots of them have had trouble with overheating with or without the EGR mod. It really comes down to engineering. The Delica was made for a JDM market, where they drive slowly and not very often. We drive them much harder than the Japanese tend to do.

http://en.wikipedia.org/wiki/Exhaust_ga ... el_engines

By feeding the lower oxygen exhaust gas into the intake, diesel EGR systems lower combustion temperature, reducing emissions of NOx. This makes combustion less efficient, compromising economy and power. The normally "dry" intake system of a diesel engine is now subject to fouling from soot, unburned fuel and oil in the EGR bleed, which has little effect on airflow but can cause problems with components such as swirl flaps, where fitted. Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of diesel particulate filters.[6] EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity.[7]

Though engine manufacturers have refused to release details of the effect of EGR on fuel economy, the EPA regulations of 2002 that led to the introduction of cooled EGR were associated with a 3% drop in engine efficiency, bucking a trend of a .5% a year increase.[8]

[floP]

Dear enthusiasts! EGR ist only active when the engine load is comparatively small. Only when You push on harder it will close completely. That is blanking the EGR won't change the top temperatures in Your diesel engines AT ALL. Our EGRs are a cheap retrofit solution to meet newer emission control standards. Earlier versions of our engines without EGR had the same rate of cracked heads. So don't worry.

By the way: Cracked heads result mainly from poor injection setting, faulty cooling systems and/or careless drivers. With sane engines and drivers heads won't crack easily.

Hope You'll understand my english,

flo
from Munich

[idiggit]

My cylinderhead had cracked with EGR open... Nothing blanked off... When I finally blanked it after getting a new head installed, it went better, faster and appeared to not go anywhere near the temps prior (but I also put a bigger diameter, shorter and less restrictive exhaust on and put a new rad, water pump) in as well...

How much diffrence will a larger bore exaust make for engine temp? not too concerned about power, but does it make a diffrence for optimizing running temp/performance?

Cheers.

[Rattlenbang]

I just read an online article about this where they tested a big V8 diesel towing a trailer, and while it gave a boost in power it didn't effect EGT.

[FalcoColumbarius]

It occurred to me today: the whole purpose of EGR is to reduce cylinder combustion temperatures, ostensibly to prevent NOx formation. Deleting EGR is a common mod for the L300. I'm wondering if a consequence of that is the higher temperatures that we see damaging heads? After spending a lot of time and money replacing this cracked head, I'm wondering if it wouldn't be smartest to restore that function. Has anyone ever considered this?

I had an argument with DeliCat that after a hundred years of successful business ventures Mitsubishi must have some idea of what they're doing. He suggested that it was not Mitsubishi's idea but some bureaucratic official's idea and that Mitsubishi just towed the line. So I made it a point to check my EGR valve, as I was running at a good temperature, had power and good fuel economy. To my surprise my EGR valve was blocked up with what appeared to be glazing putty, so I cleaned it out and polished it and put it back in. Well.... I lost power in the performance of my engine; my fuel economy went from 8.5 kilometres per litre to 6 (city); the engine started running quite hot and I had clouds of soot emitting from the tailpipe. I was chuffed, so I blocked it off. My power got better; economy went back up the 25 or 30% that it lost during this exercise, soot cleared up and my engine ran noticeably cooler.

I got to thinking about this. The idea to recirculate inert gas into the chamber to cause less fuel to be burned seemed just silly to me. Why not just put less fuel in? The idea that this inert gas would cause the engine to run cooler because it displaced some of the oxygen thereby making the explosion in the chamber smaller, ergo cooler didn't add up either. For one, the inert gas in question has just very recently been the product of another explosion and is very, very hot. How would pumping very hot gas back into the engine cause the motor to run cooler?! Would this not create more Nox emissions?

I keep thinking that I must have missed something and how could this futile concept happen at such a high level of government and technology? Then I had a discussion with the mayor of my city where he claimed that the speed bumps that are turning up everywhere in the streets are decreasing our "carbon footprint" on the Earth. Right. Slow down and speed up; slow down and speed up ~ that should create less pollution. Really? The posted speed is 50 KPH yet when once I hit one of these bumps at 45 KPH I was airborne for a second or two. Gee whizzickers, that's a safe situation! When one takes a closer look at the evidence then it's not such a long assumption to consider the whole EGR issue as being a product idiocy at the higher echelons of humanity.

Falco.

[yojimbo]

Falco, the gasses introduced are relatively cooler, the intention isn't to not burn fuel, its to reduce the speed of the flame front to keep peak temperature below the level at which nox forms. Not burning all of it is somewhat a side effect.

[nxski]

This is all above my head, I went to school for architecture and building engineering so I won't comment on how the system works but my aircare results were far better after blanking the egr. I was generating 1/3 the amount of CO2!

[FalcoColumbarius]

Falco, the gasses introduced are relatively cooler, the intention isn't to not burn fuel, its to reduce the speed of the flame front to keep peak temperature below the level at which nox forms. Not burning all of it is somewhat a side effect.

Oh, come on... have you every grabbed onto an exhaust manifold after the engine has been running a while? I figure the exhaust gas travels a total of two feet before re-entering the chamber, mixing with fresh air along the way... When you think about this, the idea is the antithesis of, say an intercooler?

You mention side effects, kind of reminds me of American medicine adverts (side effects of this product include: vomiting, diarrhoea, certain processes of neurosis, migraine headaches, kidney failure, liver disease and may not include coverage from medical assurance. See you doctor for more details).

Falco.

[yojimbo]

Well I don't mind if you don't believe me, but in countries where nox is measured, they fit egr valves, in countries that don't, we take them off.

[nxski]

Well I don't mind if you don't believe me, but in countries where nox is measured, they fit egr valves, in countries that don't, we take them off.

It's my understanding that an egr will lower NOX bit increases CO2

[Dino]

That is correct Nxski. NOx is created when high heat binds Nitrogen and Oxygen together. It is a particulate matter and is proven to be a contributor to smog pollution. However it is not poisonous like Carbon Monoxide.

As stated before the EGR valve routes exhaust gasses back into the intake under specific load situations to help lower the combustion temperature and reduce the amount of NOx that is created. Keep in mind that the magic number for the creation of NOx is 2800*F. Now take that into account that with your pyrometer probe in the exhaust manifold you would be pulling to the side of the road at 1200*F, that goes to show how much cooler your exhaust gasses are from combustion temperature.

It must also be noted that when you are cooling the combustion chamber you run the risk of cooling the fuel jet from the injector which will decrease the atomization of the fuel resulting in a greater amount of unburned fuel, hence less power and more smoke, also greater amounts of Carbon Monoxide.

[bbisset]

This is a very interesting thread! Is there a link someone can toss me for more info and/or how-to on "EGR blanking"?

Brian

'95 Pajero
'91 Surf
'97 Harrier

[yojimbo]

There's a few, basically, take it off and fit blanking plates, uk ebay has a few for 4d56t. My emissions at test have been much lower since, havent noticed any other gains, but I havent noticed any losses either. it is less smokey from a subjective perspective. Maybe the point is, it keeps working, day in day out with no smoke and crap.