EGR Removal
Thread Starter
Racer
Joined: Jun 2002
Posts: 428
Likes: 0
From: Dallas Tx
EGR Removal
What does removal of the EGR flow do to engine function?
I have a 95 LT-1, and I understand the OBDC codes, ie, it is necessary to leave the solenoid and valve in place to avoid setting codes. I am talking about simply removing the EGR feed pipe and blocking the hole. I also understand that the EGR functions at part throttle only,and is supposed to reduce peak combustion temperatures so as to reduce NOx formation.
Presumably the closed loop PCM still maintains a proper air-fuel ratio for the cats, and the spark advance still does its thing, complete with knock sensor.
But without the EGR, the intake charge should be cooler, as well as totally undiluted. For any given throttle setting, this should mean more power, or conversely, less throttle required for a given power--- better fuel efficiency.
Just like in the old days pre-emission.
With the current 3-way catalyst, reduction of any NOx occurs automatically anyway , so I would think emissions should not be affected significantly. So why does the service manual talk about overheating and knocking and emission test failure as consequences of no EGR?
The 96 LT-4 does not use EGR, and Chevy says it is because the LT-4 cam has more overlap, which allows more exhaust dilution. Is there a difference in the spark advance map at part throttle also? I had a pretty spicy 69 Vette 350 that never overheated or detonated, and the LT-4's obviously do not overheat either. What gives?
Is anyone out there enough of an engineer and professor to explain this seemingly contradictory set of facts? Are there either Fuel Mix or Spark Advance issues with blocking the flow? Thanks
I have a 95 LT-1, and I understand the OBDC codes, ie, it is necessary to leave the solenoid and valve in place to avoid setting codes. I am talking about simply removing the EGR feed pipe and blocking the hole. I also understand that the EGR functions at part throttle only,and is supposed to reduce peak combustion temperatures so as to reduce NOx formation.
Presumably the closed loop PCM still maintains a proper air-fuel ratio for the cats, and the spark advance still does its thing, complete with knock sensor.
But without the EGR, the intake charge should be cooler, as well as totally undiluted. For any given throttle setting, this should mean more power, or conversely, less throttle required for a given power--- better fuel efficiency.
Just like in the old days pre-emission.
With the current 3-way catalyst, reduction of any NOx occurs automatically anyway , so I would think emissions should not be affected significantly. So why does the service manual talk about overheating and knocking and emission test failure as consequences of no EGR?
The 96 LT-4 does not use EGR, and Chevy says it is because the LT-4 cam has more overlap, which allows more exhaust dilution. Is there a difference in the spark advance map at part throttle also? I had a pretty spicy 69 Vette 350 that never overheated or detonated, and the LT-4's obviously do not overheat either. What gives?
Is anyone out there enough of an engineer and professor to explain this seemingly contradictory set of facts? Are there either Fuel Mix or Spark Advance issues with blocking the flow? Thanks
