E.G.R. and the Diesel - Q&A

[Doc Tinker]

The subject of EGR systems on diesels came up in the "Other" forum and I thought it would be a nice fresh topic to discuss. In the mean time, maybe some of us will get our names printed in an upcoming TDR magazine when they print an article using some of our intelligent discussion on the subject



Would someone like to take the time to explain the function of the EGR and how it would help or hinder the diesel engine. And tell us where it might be located if it is included on the 2004 Cummins engines.



From my experience with the GM v-8 diesels the EGR valve is located inside of the intake manifold. You can see it when you pull of the air filter housing and there is a ton of soot stuck to the whole inside of the intake.



One advantage that I can see is the possible shortened warm up time, in cold weather, but it never seemed to have that effect on the GM diesels.



Doc

 

[Rick Comenzo]

Diesel EGR Valves

Doc, The purpose of an egr valve in a gasoline or diesel engine is to lower the combustion chamber temperature. I'm told at temperatures above 2500 degrees NOX is formed. By introducing cooler exhaust gases in a specific metered quantity, the combustion temperature is lowered, and lowering NOX formations. The problem with diesel egr systems I'm told is the lubricating oil near the cylinder rings will have more soot to deal with,having soot from combustion and soot entering through the intake system. Usually egr valves are located downstream from the air inlets. Supposedly chevron Delo and Shell Rotella oils are being reformulated to prevent sludge buildup from the additional soot in the engine. Hope this helps. Rick.

 

[nickleinonen]

say no to egr

gm diesels [and others... ] with the egr systems have had problems with their crankcase vent. system... on the gm 6. 5td the crankcase vapours are sucked into the air inlet pre turbo so they are burned off so you don't get that crankcase smell [not very pleasent i think] but when you introduse egr soot into a slightly oily intake manifold, man does it make a mess. the soot and oil combine to make a vasoline like black mess... how about having a good size coating in the intake of that and having it break off and go into a cylinder. . it could be very damaging. the egr system on diesel and gasoline engines is to operate at light load. under full load when you need full power it is not to be functional. i say fu*# the egr system... you can get the same resulst by going to vvt cam designs in gasoline engines [gm did that on the 4. 2 I6 in the trailblazer] or going to the hydraulic actuated valves on diesels. just delay the close of the exhaust valve a bit soon to leave a bit of exhaust behind.



soot traps work on diesels though... and they could be made to be serviceable. have them burned clean in a oven every year for a cheap price and easily changeable and that would be a good way of cleaning up the soot. .





the new common rail technology is pretty much year 2000 tech. and egr tech is what... 1980's... modern times need modern solutions. you could also change the injection pulse profile to reduse nox. slightly heavier first pulse then delayed 2nd & 3rd pulse to afterburn but when pressures are lower... more soot, but less nox

 

[Speedo]

EGR

Most of the engine makers who signed the consent decree with

EPA have gone with cooled EGR to become emissions compliant

while Cat has gone with leaving exhaust gases in the combustion

chamber through cam timing on the exhaust valves. Cat didn't

meet the 10-1-02 deadline though.



Gus

 

[Skydiver]

P.C.V ?

Not to change the subject.

Will the new cummins be using PCV's?

Reason I'm asking is that when I would change the air filter on our old 81 non-turbo 300-D Benz the intake manifold would have would have 1/4 inch of black sludge in it.

Thanks Tim

 

[drees1]

EGR

EGR creates lower "peak" combustion temps by diluting the air with exhaust gas. The peak temps are momentary, but are where all the NOx emisson is formed.



They route exhaust gas from the exhaust system, back to the intake. They range from simple, using check valves, to complex with electronic control valves and heat exchangers to lower the exhaust temp.



I don't believe there is any benefit to using them other than emissions reduction.



They will increase the cost, service, and complexity of our engines as mentioned.



The diesel is now over 100 years old and is aproaching the end of it's life cycle if emissions reduction continues. As cars added converters in 1975, and went electronic, diesels are begining to go to aftertreatment and other mechanical devices to go beyond what electronic control can do. There is continued development on fuel spray and basic combustion too. Any one want to guess how much longer the diesel will last in vehicles? 20 years max is my guess. Sooner or later CO2 will be limited, and then it will be over. Any one care to comment???



Doug Rees

 

[jalberring]

Re: EGR

Originally posted by drees1



Any one want to guess how much longer the diesel will last in vehicles? 20 years max is my guess. Sooner or later CO2 will be limited, and then it will be over. Any one care to comment???



Doug Rees

Doug, I remember reading somewhere (may have been the TDR magazine) that CO2 is inherently lower in diesel emissions. I'm not sure of the actual value but the diesel engines were significantly lower than gasoline. Also, as far as the diesel only lasting 20 years, the article stated that more than half of new cars sold in Europe are diesels. Europe has strict emission laws but they are biased towards helping the diesel. We are opposite in the states and our laws favor gasoline engines.



These are just the findings from the article. I have no personal knowledge on the matter.

 

[TPyle]

Cat has gone with leaving exhaust gases in the combustion chamber through cam timing on the exhaust valves. Cat didn't

meet the 10-1-02 deadline though.

That is only part of what Cat is doing. Cat has developed ACERT (Advanced Combustion Emissions Reduction Technology). This will be accomplished by controlling air management through the use of said cam timing plus an electronically controlled wastegate on the turbo(s), yes, certain engines will use compound turbocharging. A fuel temperature stabilization system will be employed to maintain fuel temps between 86F and 157F (will increase injector life during cold operation). Cat will use pilot infection for more complete fuel burn. Pistons will have a reshaped dome and improved ring package. They will also use diesel oxidation catalyst (cat converters) integral with the mufflers (no more straights!). This media will have larger holes that the honeycomb design of automotive cat converters. 300 holes/square inch vs. 400 holes /square inch. The consent decree of '98 states that who ever (engine manufacturer) comes up with the technology that works the best has to sell it (after licensing it of course) to everybody else. There is no stipulation as to what can be charged. Cat has been spending $2M a day for the past 3 years on this technology so it will be costly to purchase. I will assure you that unless Cummins can get its credit rating up from junk status this will not bode well.



As to why Cat didn't meet the deadline. They were not ready with ACERT so rather than not be able to sell an engine they chose to pay the NCPs and take the time to get it right. Remenber that in the next few years off raod diesel engines will have to meet the same emissions standards as on road engines. Cooled EGR will not work on a bulldozer or other slow moving machine because cooled EGR needs ram air. Think about all the Cummins engines in off road applications and you will understand the position that the company is in.

 

[drees1]

Why does the cooled EGR need ram air? All the examples on display at the Lousiville truck show, (Cummins, Detroit, Mack, Volvo) used a heat exchanger to the water jacket.



Do you know if CAT has scrapped HEUI for the 3406?



Doug Rees

 

[drees1]

Re: Re: EGR

Originally posted by jalberring

Also, as far as the diesel only lasting 20 years, the article stated that more than half of new cars sold in Europe are diesels. Europe has strict emission laws but they are biased towards helping the diesel. We are opposite in the states and our laws favor gasoline engines.



These are just the findings from the article. I have no personal knowledge on the matter.

I know what your saying. I'm thinking how tough the 2007 emissions are, and thats only 5 years from now. Steam locomotives went 100 years and were replaced by diesels almost overnight. (granted for a different reason) I just wonder, if all the cost of forcing the internal combustion engine to do what it can't, very easily will be met head on with something like the fuel cell technology. If we look at past emissions levels, and the cost to reduce them, it seems like we are approaching a brick wall, with greater R&D costs, Product costs, and emission levels so low already.



Doug Rees

 

[TPyle]

Doug,



Yes the cooled EGR engines use a heat exchanger and jacket water. But the absorbed heat from the jacket water is dissipated by the primary cooling system. Thus the need for ram air created by the truck cruising down the road. Another thing to consider about cooled EGR is the sulfuric acid created in the combustion chamber and pumped all trough the engine by the oil pump. Detroit had to go to stainless steel valves however you can't make seals and o-rings and bearings out of stainless steel. Thus the need to run CI-4 in these new engines.



As far as HEUI on the C10/12/15? I know that it has will be incorporated into the C-12 so I can only imagine that it would for the C-15(3406). When I find out I'll share what I can.

 

[A Johnson]

TPyle, I just heard a rumor today that Cat was backing up and going with cooled EGR, at least for the automotive market. This was not from a Cat source, and as I'm sure there is all kinds of marketing dissinformation going on due to the potential market gain/losses, I'm wondering if you are in a position to confirm or deny this.



I have allways been envious of Cat as they allways seem to be on the leading edge and Cummins ends up as the underdog in the HP/Torque, or new technology race.



If in fact ACERT technology does become compliant, I might as well kiss my job goodby and see if they need any mechanics across the street. I think I'm too fat for the yellow coveralls though.



A Johnson

 

[R.E. Miller]

For What it's Worth...

At work, they wheeled out a "new" ISM complete with it's 2 ecm's, VGT, and yes... egr. It is the future, learn to deal with it is the attitude. the egr system on the ISM mounts above the exhaust manifold, and has sensors and controls for everthing from egt, turbo speed, coolant flow, metering for both coolant and cooled eg's. The cooler itself looks a lot like the exhaust manifold in dimentions, but the system in general causes more clutter in an already cramped environment. I will let you know when I see one, at will deal out the news.



BTW, after treatments are like a small bandage on a hollow point gunshot wound. But don't worry, if it all fails, we can carpool with the big wigs at the EPA, they most likely drive SUV's so we'll all fit :-laf



Russell

 

[TPyle]

A Johnson,



Cat looked at 5 different technologies including cooled EGR to meet the EPA mandated 2. 5 NOx g/hp-hr. The reason that they didn't go with cooled EGR is because it is a stop gap solution. Cummins, Detroit, Mack, EPA... have all admitted that cooled EGR will not meet 2007 emissions regs of 0. 05 NOx g/hp-hr. Off road diesels will have to meet this same requirement. As stated earlier cooled EGR will not work in a machine. It requires ram airflow across the radiator to handle the added heat rejection into the cooling system. The On-Highway division of Cat develops and tests the technology for the the Off-Highway division. The technology developed had to work in both duty cycles.



You are absolutely correct that there is disinformation as well as misinformation. I had a sales meeting tonight with a Freightliner dealer to dispel just that.

 

[Texas Diesel]

My answer to EGR, just say no.



Back in 95 a spent . 22 shell got sucked in the vacum line that operates the EGR on the 318 (gas) engine. Came out once a year to pass emissions and then would sucked back in. Been that way for 190,000 miles despite some advice that blocking the EGR valve would melt my pistons or whatever. As a matter of fact, once the CAT's guts fell out, some lead shot got spilled in the fuel tank, wonder if this is why the 318 is so happy @ 190k of HARD use, 4wd, towing etc.



Happiness is no Catalytic converter or EGR valve!!!!



The worthless thing will only introduce soot back into the engine and oil.

 

[nickleinonen]

Happiness is no Catalytic converter or EGR valve!!!!

 

[kaffine krazed]

I think I understand how an EGR valve works on a gas engine. The gas engine has to maintain a 14. 7:1 air fuel ratio. So you add exaust gas to take up space since it is mostly inert gas and you get lower combustion chamber temps because there is less fuel being burned. On a diesel engine though the air fuel ratio is not maintained and varies alot. So with an egr valve you are going to add hot gas back into the combustion chamber to lower the temp of combustion. Even if it is a cooled egr system that will lower the temp of the exaust gas to 190-200 degrees since it is cooled by the engine coolant. And if you have a good air to air aftercooler your intake air temp shouldn't be over 150 degrees. So how does adding hotter gasses back into the combustion chamber cool it to prevent NOx? And also with diesel the exaust gas wont be as inert to the combustion procees as in a gas engine since diesels normally run lean there will still be O2 on the exaust. I know I'm missing something since egr suppousedly works on diesel. Anyone know what I am missing? Thanks.

 

[R.E. Miller]

A. Johnson/T. Pyle,

I think that you both have very good points. I think I am in Johnson's boat though, we might be both swimming through the blue sea that leads to the yellow brick road if the Acert comes out and does what I think it might. Cummins this and Cummins that, if Cat really is investing there time/$$ on something that will do both (btw, I am one of the people who thinks this can/is happening) then guess who will get the last laugh?

I am not convinced that the egr situation won't look something similar to the Hindenburg flight. It is just like many other technological innovations of our time and age, good theory with minimal testing and proof.



Russell

 

[Doc Tinker]

This is all clear as mud

 

[Doc Tinker]

OK - here is something I found about ERG Valves in relation to gasoline engines. I'm sure some of this relates to EGR Valves on diesels. This is starting to make some sense, but I'm still out in left field.





- - - - - - - - -



Definition: The EGR valve is the main emissions control component in the exhaust gas recirculation system. The valve is located on the intake manifold, and opens a small passageway between the exhaust and intake manifold to allow a metered amount of exhaust to flow back into the engine. This reduces combustion temperatures and helps control the formation of oxides of nitrogen. The EGR valve is opened by the application of vacuum to its control diaphragm. Some also require a certain amount of exhaust back pressure before they'll open. On newer vehicles, the valve is electronic and uses one or more solenoids or a small stepper motor. The valve should remain closed while the engine is cold and at idle. It should only open once the engine has warmed up and is running at part-throttle. If the valve sticks shut (or is disconnected), NOX emissions will soar and detonation will often result (See Detonation and Spark Knock). If it sticks in the open position or fails to close all the way, it acts like a vacuum leak resulting in a rough idle, hesitation and possible stalling.





- - - - - - - - - - -



What happens if it sticks open on a diesel engine?



What happens if it sticks closed on a diesel engine?







Doc