Another question for the experts

[DBoggs]

I know it is not recommended to drive the 6. 7l at lower speeds and light loads. However that's not always possible. This question would apply for both auto and manual transmission trucks.



While driving in a low speed, low load situation, ie: city traffic, winding roads, etc... would it be better to downshift and run the engine at a higher rpm? Say 2000-2400rpm. This in my opinion would keep the engine from lugging and therefore producing as much soot. Plus it has the added benefit of better braking from the engine brake. Am I full of soot on this hypothesis due to the egr or is it a sound practice to continue doing?



I'm just trying to get some ideas on how to prevent potential problems without having to delete the egr and dpf, though that may come at some time in the future. Especially if I start to have issues.



Thanks for any ideas and opinions.



Duane

 

[cojhl2]

I would never run an engine any faster than necessary to move the load without 'lugging" it.



Why put more piston miles on it than necessary?



Not only that people driving next to you would think you are showing off. .



I don't run my 90 faster than 2000 at any time. 2000 is 60 and I'm stuck at taht speed. Wish I had an OD.

 

[Bob4x4]

I don't think so. If you could see the scanner during a regen there is less soot load at under 2k. The bigger issue as I see it to keep the turbo active so it stays clean by it's scaper. Egts are also needed to keep everything working well so my guess the more eficient intercoolers will hinder the processes as long as the system is left intact.

 

[jimnance]

The objective is to raise exhaust gas temperatures to the point that they activate the DPF and clear the soot accumulation. I don't think that changing engine RPM with a constant load will alter it enough to be significant.



As far as soot production is concerned I suppose there may be a particular RPM that minimizes it, but I wouldn't assume that it would be a higher RPM. With the amount of programming and computer control you'd need to find someone that understands the emissions profile of the engine to know for sure.



Piston speed, within normal operating ranges does not significantly change the life of the engine. Other factors like service intervals and how often the engine is operated has a greater effect. An engine run eight hours a day, seven days a week, and serviced regularly will last many more miles than an engine run infrequently or with inadequate service. This is one of the reasons that OTR rigs get terrific service from their Cummins engines.

 

[grasmo]

I think lugging would put more wear on the rotating assy. and increase egt's ... . who knows a smart man will come out with a way to regen at will with a switch inside the cab , that way say you are on the highway at speed and know you are approaching say Atlanta (rush hoursssss) traffic you could regen before you get there and then not even worry about it. Or straight pipe it. I invite any of you guys to drive mine and see for yourself what you are missing if you are coming to the Tallahassee fl, area p. m. me and I'll meet up with you and let you try it out ... . Breathalyzer and I. Q. test nice but not required !

 

[DBoggs]

What conditions trigger egr operation? Is it at all throttle levels or just under hard acceleration? Of course I realize that there are no doubt various conditions that cause it to operate no matter the throttle input but it is there to reduce cylinder temps and drop nox emissions isn't it?



As for higher vs lower rpm, if I leave the truck in D and I'm in town at 35mph for example, I'm only running about 1200 or 1300 rpm. This almost seems like a lug to me, except that there is very little load on the engine.



As for pulling the dpf and egr, believe me the thought has crossed my mind, but I don't have the extra funds to buy all the stuff right now and I can't stand when cel light is on. It irritates me to no end. Though as I said earlier I may end up doing that anyway, especially if I start having issues.



I'm just seeking to further educate myself on the operation of the emissions system so that I can hopefully prevent problems before they occur. Though that may not be possible.



Thanks

Duane

 

[Bob4x4]

OPERATION





The EGR (Exhaust Gas Recirculation) system is designed to reduce NOx in the exhaust system by reducing combustion temperatures. This is done by introducing inert gas (exhaust) into the combustion process. The intake air charge is diluted by a precisely metered amount of exhaust gas for the operating mode. For example at idle and part throttle, more EGR is introduced than at high-speed cruise conditions. A cooler (2) reduces the temperature of the exhaust gas before it is combined with the intake air, which increases the ability of the existing volume of inert gas to reduce NOx. The EGR cooler is cooled by the engine coolant.



The EGR system contains the following components:



EGR Cooler (2)

EGR Valve Assembly (5)

EGR Valve Crossover Tube (4)

EGR Temperature Sensor (7)

EGR Valve Actuator (6)

EGR Air Flow Control Valve (8)







EGR is active at low load and speed ranges. Control of EGR flow is based on engine load and engine speed. The ECM (Engine Control Module) gathers information from engine input sensors, and after evaluating the input signals, uses a stored performance map to operate the EGR Valve Actuator (2) and EGR Airflow Throttle Control Valve (3). The calculation allows for a precise EGR flow rate.



The EGR Valve Assembly (1) is located at the left front of the engine, in the upper corner of the intake manifold. The EGR valve has two poppet valves connected by a valve shaft. Cooled exhaust gases flow from the EGR cooler to the center of the valve. When the valves open, exhaust gasses flow into the intake air stream from both the top and the bottom of the passage.



The EGR valve motor (actuator) (2) is a three-phase, brushless DC motor controlled by the ECM. The motor assembly also contains three Hall-effect sensors that detect EGR valve position.

 

[DBoggs]

Thank you sir, that was a very thourough explanation. Its what I thought but it is good to see it in writing.



Thanks to all who replied.



Duane

 

[DieselLady]

Peak torque on these engines is between 1400 and 1800 rpm. EGR is introduced more on low rpm's as it is running hotter. I use the paddle to run the truck around peak torque and alway keep the e brake on to keep the turbo free from sooting up. BTW. Adding EGR will create more soot. Advancing timing and making the engine run more efficiently will increase NOx. This is the problem engineers have had to deal with for years. More soot is very hard on the engine and DPF. More NOx is hard on emissions.
I run emissionless and have clean oil and better fuel economy.

 

[grasmo]

Diesel Lady ... . I just bought you a beer! You are one of the reasons I did the edge and dpf delete . Man what a beast!

 

[DieselLady]

Diesel Lady ... . I just bought you a beer! You are one of the reasons I did the edge and dpf delete . Man what a beast!

Awesome, glad you are happy with your truck. I still am amazed at how much difference it makes in HP and performance. Fuel economy too.

Thanks for the beer!Oo.