Chevy and GMC Duramax Diesel Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!
1 - 9 of 9 Posts

·
Premium Member
Joined
·
384 Posts
Discussion Starter · #1 ·
So, after throwing an EGR code or more, I realized... I'm not completely sure what my EGR does for me, why I need it, or why I just don't get rid of it.?

So, at Thanksgiving, I spoke to my cousin, who happens to be a lead emission compliance engineer at Mack... umm.. I mean Volvo :rof .... Anyway, he explained a lot to me, and I thought I'd share it with ya'll.

Here is his extended written response, which graced my inbox at midnight on Thanksgiving.

"Ben,

You asked me about EGR and what would happen blocked off the EGR on your engine. I thought more about it this evening, and I'm not satisfied with the answer I gave you earlier, so I'll do a better job this time.

The primary purpose of EGR is to reduce NOx for emissions compliance. The exhaust gas is pulled from the exhaust manifold, flowed through a cooler, and then mixed with fresh air before going into the cylinder. Lower boost temperatures result in lower NOx during combustion since NOx is extremely temperature dependent. There also exists a trade off of NOx and diesel particulate matter. Generally speaking, disesl particulates decrease with increasing NOx if the engine calibration is optimized. Because there is an emissions requirement for low NOx, this increases the particulates, so a DPF is required so that the engine can also pass the particulate emissions requirements. EGR also effects combustion temperatures, so it effects the amount of heat energy rejected to the engine coolant. The measured amount of heat energy rejected to the coolant is used to determine the radiator cooling package requirements for the engine. Injection timing, injection pressure, EGR, and Turbo position (if equipped with a variable geometry turbo) are all optimized for engine performance, fuel economy, and aftertreatment regeneration efficiency.

All that being said, what if EGR is removed from the equation on an engine that was developed with EGR? The main benefit of removing EGR is that you would likely see an increase in fuel economy. This is a plus, but some long term disadvantages may come with it. If your engine has a feedback on EGR flow, you will likely get an engine fault code for a problem in the EGR system, and the engine may start to run calibrated settings without EGR. There is likely some intelligent ECU programming to prevent someone from simply disabling EGR without some kind of negative consequence (i.e. power derate). If your EGR system does not have feedback, it will run open loop settings, so it thinks you have EGR, but actually you don't. In this case, you will likely run into some pretty major problems long term. Feedback or no feedback, your radiator is sized for the engine to run with a certain amount of EGR, so you probably will not have adequate cooling capacity running w/out EGR. If some of your engine temperatures get too high, the engine will derate power for durability reasons. Essentially, your engine is optimized as a system to run within hardware limits so that it will last for a long time. Changing the engine from how it was optimized by the manufacturer will change the characteristics of combustion and likely reduce the durability of your engine.

There is also a consequence of removing aftertreatment components from the truck. Removing an aftertreatment component reduces the exhaust backpressure on the engine. For given actuator settings, this will help you to achieve more power, but again, this can be at a price. Typically, with reduced exhaust backpressures you will see increased turbo wheel speeds. If your wheel speed is increased too much, this will reduce the life of your turbo. Drastically changing exhaust backpressure will also effect combustion characteristics which again could result in exceeding engine design limits that otherwise would not be exceeded.

Personally, if I bought a newer truck with a diesel engine, I wouldn't touch a thing on it. Some guys will claim success through making alterations to the engine hardware or software, but it will likely result in durability consequences down the road. The engine should have enough margin built in that small changes won't have a noticable impact, but big changes could mean big problems long term.

Hopefully this information is helpful."

...and then


"I take back the radiator comment. Running higher NOx levels (less EGR) generally reduces the amount of heat rejected to the coolant. Perhaps that is because you are cooling less high temp exhaust gas. You have to factor in how the engine was calibrated for heat rejected to the exhaust to keep conditions for the aftertreatment optimized. I still wouldn't mess with it."
 

·
Registered
Joined
·
3,028 Posts
good write up
 

·
Premium Member
Joined
·
1,972 Posts
With that said I installed the EGR blocker plate and threw no codes. I also no longer have the exhaust soot entering back into my motor
 

·
Registered
Joined
·
35 Posts
nice,but remember they build this trucks to standard emissions but they also leave alot of extra play with them, they just do not build them to the limit for example the GOV that prevents you from going so fast, ok its removeable with the right tool etc..but nice article and do not be afraid to up grade your truck...
 

·
Premium Member
Joined
·
384 Posts
Discussion Starter · #5 ·
Well... this is intended to be more or less of a general explanation of the EGR. Not so much a deterrent to upgrade.

This is not Duramax specific, but relevant none the less.

Just a different POV from a guy who knows his stuff.
 

·
Premium Member
Joined
·
1,972 Posts
That is one of the benefits of the Forums. Newer trucks come from the factory with the DPF filters....Government required MPG destroyers. It's all about the cash disguised as environmental concerns. The more fuel you burn the more they collect in fuel taxes.
 

·
Registered
Joined
·
1,069 Posts
That is one of the benefits of the Forums. Newer trucks come from the factory with the DPF filters....Government required MPG destroyers. It's all about the cash disguised as environmental concerns. The more fuel you burn the more they collect in fuel taxes.
Never thought about it like that. Good point. However, I still think emissions is still the primary mindset in things like EGR and DPF.
 

·
Registered
Joined
·
6 Posts
So, after throwing an EGR code or more, I realized... I'm not completely sure what my EGR does for me, why I need it, or why I just don't get rid of it.?

So, at Thanksgiving, I spoke to my cousin, who happens to be a lead emission compliance engineer at Mack... umm.. I mean Volvo :rof .... Anyway, he explained a lot to me, and I thought I'd share it with ya'll.

Here is his extended written response, which graced my inbox at midnight on Thanksgiving.

"Ben,

You asked me about EGR and what would happen blocked off the EGR on your engine. I thought more about it this evening, and I'm not satisfied with the answer I gave you earlier, so I'll do a better job this time.

The primary purpose of EGR is to reduce NOx for emissions compliance. The exhaust gas is pulled from the exhaust manifold, flowed through a cooler, and then mixed with fresh air before going into the cylinder. Lower boost temperatures result in lower NOx during combustion since NOx is extremely temperature dependent. There also exists a trade off of NOx and diesel particulate matter. Generally speaking, disesl particulates decrease with increasing NOx if the engine calibration is optimized. Because there is an emissions requirement for low NOx, this increases the particulates, so a DPF is required so that the engine can also pass the particulate emissions requirements. EGR also effects combustion temperatures, so it effects the amount of heat energy rejected to the engine coolant. The measured amount of heat energy rejected to the coolant is used to determine the radiator cooling package requirements for the engine. Injection timing, injection pressure, EGR, and Turbo position (if equipped with a variable geometry turbo) are all optimized for engine performance, fuel economy, and aftertreatment regeneration efficiency.

All that being said, what if EGR is removed from the equation on an engine that was developed with EGR? The main benefit of removing EGR is that you would likely see an increase in fuel economy. This is a plus, but some long term disadvantages may come with it. If your engine has a feedback on EGR flow, you will likely get an engine fault code for a problem in the EGR system, and the engine may start to run calibrated settings without EGR. There is likely some intelligent ECU programming to prevent someone from simply disabling EGR without some kind of negative consequence (i.e. power derate). If your EGR system does not have feedback, it will run open loop settings, so it thinks you have EGR, but actually you don't. In this case, you will likely run into some pretty major problems long term. Feedback or no feedback, your radiator is sized for the engine to run with a certain amount of EGR, so you probably will not have adequate cooling capacity running w/out EGR. If some of your engine temperatures get too high, the engine will derate power for durability reasons. Essentially, your engine is optimized as a system to run within hardware limits so that it will last for a long time. Changing the engine from how it was optimized by the manufacturer will change the characteristics of combustion and likely reduce the durability of your engine.

There is also a consequence of removing aftertreatment components from the truck. Removing an aftertreatment component reduces the exhaust backpressure on the engine. For given actuator settings, this will help you to achieve more power, but again, this can be at a price. Typically, with reduced exhaust backpressures you will see increased turbo wheel speeds. If your wheel speed is increased too much, this will reduce the life of your turbo. Drastically changing exhaust backpressure will also effect combustion characteristics which again could result in exceeding engine design limits that otherwise would not be exceeded.

Personally, if I bought a newer truck with a diesel engine, I wouldn't touch a thing on it. Some guys will claim success through making alterations to the engine hardware or software, but it will likely result in durability consequences down the road. The engine should have enough margin built in that small changes won't have a noticable impact, but big changes could mean big problems long term.

Hopefully this information is helpful."

...and then


"I take back the radiator comment. Running higher NOx levels (less EGR) generally reduces the amount of heat rejected to the coolant. Perhaps that is because you are cooling less high temp exhaust gas. You have to factor in how the engine was calibrated for heat rejected to the exhaust to keep conditions for the aftertreatment optimized. I still wouldn't mess with it."
So the problem with THIS write up is this guy works on Mack…not Duramax. Duramax guru’s TOTALLY DISAGREE with this opinion. While it is a good write up it doesn’t pertain to duramax because it’sa WHOLE DIFFERENT BREED OF DIESEL ENGINE. Get in touch with Kory Willis in Lake Charles, Louisiana. He developed the FIRST EFI LIVE TUNES for Duramax.
 
1 - 9 of 9 Posts
Top