I don't think anyone can dispute the fact that in 2002, when egr was mandated on heavy heavy duty engines (the ones in big trucks) that fuel mileage suffered. At that time, the mandates called for 20% egr in the intake air. In 2007, mileage took another hit, as egr rates were increased to 40%. In 2010, when the next round hits and egr rates are spiked even higher, efficiency will drop again. The smaller engines have just followed the path of their larger siblings.
Why? It's simple physics. EGR is another word for "oxygen free." Exhaust gases contain no oxygen, hence they do not support combustion. What they do is absorb heat and exhaust it with no benefit. There still has to be enough oxygen for the fuel to combust completely, so more and more total air volume has to be crammed into the cylinders. That surplus air is then compressed, which takes energy which has to come from the combustion event since there's no free lunch. This causes a drop in BSFC. The fact that the timing is also retarded from the optimum also means a big drop in efficiency and an increase in retained heat, which necessitates larger cooling systems and more robust systems that are more temperature tolerant.
The addition of SCR means that the timing can again be optimized and the egr rate can be reduced or even eliminated, both of which will cause efficiency gains.
Detroit Diesel, in 1997 or thereabouts, produced a diesel engine that had a BSFC of less than .30 lbs of diesel per brake horsepower hour. Today's engines are nowhere close to that. Personally, I look forward to the SCR engines, as we should see improvements of at least 5% in the first year and as the systems mature, perhaps even more as the mechanical functions revert closer and closer to the ideal combustion events of the past generations while still keeping emissions in check. I also predict that the needed urea w/ soon be widely available at reasonable cost.
Combining this new (to the US) technology with the more robust mechanical systems of todays engines spell increased longevity and better value to consumers through increased durability and fuel economy when compared to the engines of today.
It's also mighty darn presumptous of you to doubt my knowledge as well. As a performance engineer for a major engine manufacturer, all of my comments are based on results seen in our labs and in trucks, not from someone on an bulletin board that decided to play shadetree mechanic. EGR kills fuel economy plain and simple. And why would a much smaller dpf use more fuel than a larger dpf to oxidize soot?
pupeperson wrote: I don't think anyone can dispute the fact that in 2002, when egr was mandated on heavy heavy duty engines (the ones in big trucks) that fuel mileage suffered. At that time, the mandates called for 20% egr in the intake air. In 2007, mileage took another hit, as egr rates were increased to 40%. In 2010, when the next round hits and egr rates are spiked even higher, efficiency will drop again. The smaller engines have just followed the path of their larger siblings.
Why? It's simple physics. EGR is another word for "oxygen free." Exhaust gases contain no oxygen, hence they do not support combustion. What they do is absorb heat and exhaust it with no benefit. There still has to be enough oxygen for the fuel to combust completely, so more and more total air volume has to be crammed into the cylinders. That surplus air is then compressed, which takes energy which has to come from the combustion event since there's no free lunch. This causes a drop in BSFC. The fact that the timing is also retarded from the optimum also means a big drop in efficiency and an increase in retained heat, which necessitates larger cooling systems and more robust systems that are more temperature tolerant.
The addition of SCR means that the timing can again be optimized and the egr rate can be reduced or even eliminated, both of which will cause efficiency gains.
Detroit Diesel, in 1997 or thereabouts, produced a diesel engine that had a BSFC of less than .30 lbs of diesel per brake horsepower hour. Today's engines are nowhere close to that. Personally, I look forward to the SCR engines, as we should see improvements of at least 5% in the first year and as the systems mature, perhaps even more as the mechanical functions revert closer and closer to the ideal combustion events of the past generations while still keeping emissions in check. I also predict that the needed urea w/ soon be widely available at reasonable cost.
Combining this new (to the US) technology with the more robust mechanical systems of todays engines spell increased longevity and better value to consumers through increased durability and fuel economy when compared to the engines of today.
Thank you!
We are seeing a minimum of 5% increase in fuel economy in our early testing of SCR and, as you said, expect more as we refine our software. We still have 15+ months to go before we start selling these engines. This is the reason why Cummins abandoned MEGR in the ISX for 2010.
I agree Donn. Think of all the DPF equipped vehicles out there getting 3-7 mpg's less than they should. Now we have to drill that much more (pollution) refineries have to produce that much more (pollution) ship that much more (pollution) etc...etc...
My brother is seeing 20+ mpg in his DPF/Cat/DOC-less 2007.5 6.7L Cummins. Up from 13-14mpg.
2006 3500 DRW LT3 Silverado MAX n ALLY CC
5" MBRP Exhaust EFI Live /Autometer Ultralite II Pyrometer
Bio-Pro 190 Bio-Diesel Processer Diesel for $.88 gal
2006 Day Dreamer 37 CDTSD
Quote: It's also mighty darn presumptous of you to doubt my knowledge as well. As a performance engineer for a major engine manufacturer, all of my comments are based on results seen in our labs and in trucks, not from someone on an bulletin board that decided to play shadetree mechanic. EGR kills fuel economy plain and simple. And why would a much smaller dpf use more fuel than a larger dpf to oxidize soot?
Sorry for doubting you, but this guy and many of his colleagues say your wrong. John B Heywood PHD He wrote a book. You might have heard of it if you are an engineer? It called: Heywood, J.B., Internal Combustion Engine Fundamentals, McGraw-Hill, 1988.
Now who am I to believe? I guy on the internet who says he is an engineer and works with engines?
Or Dr. Heywood, a published author who who is peer reviewed and has writen hundreds of articles on ICE's and pollution control equipment? A guy that has a PHD in mechanical engineering has written at least two great books. A man that fly's all over the world talking about and teaching others about pollution controls on ICE. A man who is in Industrial and Government consulting for over 30 years and is a long-time consultant to Ford Motor Company, Mobil Oil Co.
I could go on and on about Dr. Heaywood.........but again, I don't want to be redundant.
If you work in or with an engine lab they must have some papers that you can point to on the net that shows EGR's kill fuel mileage. I have given several sites and one very reputable book that say the opposite. Give me a "reputable or scientific" site that says EGR's kill fuel mileage and I will take a look. I have seen nothing from you or anybody else so far except "well Billy Bob cousin say's....."
Here is another site that talks about EGR's and how they save fuel. Fuel savings of EGR's
A lot of engine manufactures are looking at the HEDGE system.
Here is a little tast of the artical.
HEDGE, consortium sponsors at deadline
for this report are: Corning,
Cummins Engine, Hino Motors (51%
owned by Toyota), John Deere, PSA
Peugeot Citroën, Volvo/Renault
(trucks), Renault (car), Volkswagen,
Ford, Nissan, and Valeo, with “more
expected to sign on” according to HEDGE
Program Manager Tom Ryan.
Ryan explained that HEDGE technology
is based on very high exhaust gas recirculation
(EGR) rates to minimize pumping
losses and engine-out NOx emissions. Complete article
Like I said; give me some "reputable or scientific" sites that says EGR's kill fuel mileage and I will take a look. If you work for a company that publishes their data on different pollution control systems it should be easy to do.
Now if you feel your reputation is better as a mechanical engingeer or you have more published articles than Dr. Heywood please post them; I would like to see them.
~ Too many freaks & not enough circuses ~
"Life is not tried ~ it is merely survived ~ if you're standing
outside the fire"
Sorry for doubting you, but this guy and many of his colleagues say your wrong. John B Heywood PHD He wrote a book. You might have heard of it if you are an engineer? It called: Heywood, J.B., Internal Combustion Engine Fundamentals, McGraw-Hill, 1988.
Now who am I to believe? I guy on the internet who says he is an engineer and works with engines?
Or Dr. Heywood, a published author who who is peer reviewed and has writen hundreds of articles on ICE's and pollution control equipment? A guy that has a PHD in mechanical engineering has written at least two great books. A man that fly's all over the world talking about and teaching others about pollution controls on ICE. A man who is in Industrial and Government consulting for over 30 years and is a long-time consultant to Ford Motor Company, Mobil Oil Co.
I could go on and on about Dr. Heaywood.........but again, I don't want to be redundant.
Dr. Heywood isn't the only authority on ICE. In fact, there are literally hundreds of very intelligent individuals working at the research level developing tomorrow's technology. I wouldn't take everything he says as gospel since developments occur daily.
Quote: If you work in or with an engine lab they must have some papers that you can point to on the net that shows EGR's kill fuel mileage. I have given several sites and one very reputable book that say the opposite. Give me a "reputable or scientific" site that says EGR's kill fuel mileage and I will take a look. I have seen nothing from you or anybody else so far except "well Billy Bob cousin say's....."
A lot of engine manufactures are looking at the HEDGE system.
Here is a little tast of the artical.
HEDGE, consortium sponsors at deadline
for this report are: Corning,
Cummins Engine, Hino Motors (51%
owned by Toyota), John Deere, PSA
Peugeot Citroën, Volvo/Renault
(trucks), Renault (car), Volkswagen,
Ford, Nissan, and Valeo, with “more
expected to sign on” according to HEDGE
Program Manager Tom Ryan.
Ryan explained that HEDGE technology
is based on very high exhaust gas recirculation
(EGR) rates to minimize pumping
losses and engine-out NOx emissions. Complete article
HEDGE is a concept for GAS engines. DCDC is the equivelant technology for diesel engines. The problem here is the technology isn't advanced enough to take advantage of. It requires special oxygenated fuels and complex and expensive turbos. Dilute Clean Diesel Combustion
Quote: Like I said; give me some "reputable or scientific" sites that says EGR's kill fuel mileage and I will take a look. If you work for a company that publishes their data on different pollution control systems it should be easy to do.
Cummins Engine Company recently abandoned massive egr in favor of SCR for fuel economy reasons. Cummins News
Quote: Now if you feel your reputation is better as a mechanical engingeer or you have more published articles than Dr. Heywood please post them; I would like to see them.
There is a trade off between reducing NOx and PM. When you reduce one, it increases the other. EGR is used to reduce NOx levels. The higher the EGR flow and lower the NOx, the higher the PM levels. This is due to higher peak cylinder pressures and reduced power density levels. PM = unburned fuel = waste.
And sorry to say, all of this still boils down to, more fuel burned equals more pollution and more complicated technology that does not work very long costing consumers tens of thousands of extra dollars out of their pockets for something that so far NO ONE has been able to say scientifically makes any difference to the environment. This is more junk science that makes the tree huggers happy and costs our economy untold amounts of money. When will congress wake up and stop pandering to the special interest groups?
donn0128 wrote: This is more junk science that makes the tree huggers happy and costs our economy untold amounts of money. When will congress wake up and stop pandering to the special interest groups?
Wow, I can't believe I just read that.
Do you have the faintest idea what L.A., New York or Chicago would look like if all current cars ran without pollution control like they did before the 70's? You think L.A. has a smog problem now, just think what it would look like today with many times more cars on the road all puking unburned hydrocarbons out the tailpipes!
The Boy Scouts support the idea of "Leave no Trace", and it deserves some consideration in all aspects of our daily life, not just out of the trails. Isn't it a good idea to build cars with the lowest impact on the environment? Even if we weren't sure exactly what the future impact would be, it just make sense that the less pollution we generate the smaller the potential for later problems will be in the future?
If you love the great outdoors enough to own an RV and spend all your free time enjoying the beauty and serenity, why wouldn't you want to at least try to keep your impact on it minimal for preservation sake?
'04 Ford Freestar (Primary tow vehicle) '05 Subaru Forester (Backup tow vehicle) '65 Bethany popup (best popups ever made!) Looking for a tow vehicle Minivan towing
Why not. I will not dispute the facts that up till now that cleaner burning cars have helped the environment. But and this is still a big but, what would out environment be like if the auto makers could make cars that got 50MPG without all that so called pollution control equipment that cost in so many other ways? How is it that a 2006 Dodge diesel could achieve 20+MPG on the highway without the junk that is now on the new trucks and with it the best you can achieve is 16-17MPG How is it that a 15% reduction in fuel economy is better for the environment? How is it better for our economy to spend 15% more for fuel to fund terrorists? How is it better for OUR economy NOT to push for energy independence for OUR country? When I say "junk science" that is exactly what I mean. There is still no scientific proof that burning fossel fuels has done anything but make this country great while the rest of the world is still largely in the 17th century. If the government would get out of the way I have no doubt in my mind that technology could and would emerge that would product cleaner burning cars and trucks that what we see today. That is what has made this country great, invention! Not the tree huggers. I for one do not want to go back to the days of horse and buggy.
Offline
I guy on the internet who says he is an engineer and works with engines? 
Online
