EGR question
CF Veteran
Joined: May 2008
Posts: 3,018
Likes: 23
Year: 1988
Model: Cherokee
Engine: AMC242
Yes - and that's usually how the smog "techs" out here function-test the thing (disconnect the vacuum, hook up a hand pump, and pull a vacuum. Should stall out the engine, and should hold vacuum for 30 seconds or so.)
However, I think the EGR is a stupid solution to a known issue - and I can think of a couple of better ways to do it.
EGR = "Exhaust Gas Recirculation" - what you're doing is running exhaust gas back into the engine to "cool off" combustion (how you can cool off a heat reaction by introducing 1000*F exhaust gas escapes me...)
The problem with EGR? Mainly, it's introducing another failure-prone component into the system, complete with its own activation system, and exhaust gas always carries particulate carbon with it - so you're not only running hot exhaust gas back into the intake stream (and screwing up air temperatures,) but you're also coating the inside of your intake with carbon (which ends up mandating parts replacement - even though the part itself hasn't failed, it's just irretrievably coated with carbon, which either clogs up the sensing element or coats it with an insulating layer. Both bad.)
I'd even argue the merit of having it on our (relatively) low-compression engines - I've got before/after smog reports somewhere on my 87. The first test was with a failed EGR - it otherwise passed on all elements (including NOx.)
The second test was after I'd replaced the EGR - NOx unchanged, HC and CO and skyrocketed to "barely passing."
Go figure.
However, I think the EGR is a stupid solution to a known issue - and I can think of a couple of better ways to do it.
EGR = "Exhaust Gas Recirculation" - what you're doing is running exhaust gas back into the engine to "cool off" combustion (how you can cool off a heat reaction by introducing 1000*F exhaust gas escapes me...)
The problem with EGR? Mainly, it's introducing another failure-prone component into the system, complete with its own activation system, and exhaust gas always carries particulate carbon with it - so you're not only running hot exhaust gas back into the intake stream (and screwing up air temperatures,) but you're also coating the inside of your intake with carbon (which ends up mandating parts replacement - even though the part itself hasn't failed, it's just irretrievably coated with carbon, which either clogs up the sensing element or coats it with an insulating layer. Both bad.)
I'd even argue the merit of having it on our (relatively) low-compression engines - I've got before/after smog reports somewhere on my 87. The first test was with a failed EGR - it otherwise passed on all elements (including NOx.)
The second test was after I'd replaced the EGR - NOx unchanged, HC and CO and skyrocketed to "barely passing."
Go figure.
CF Veteran
Joined: Oct 2009
Posts: 2,867
Likes: 16
From: Fauquier County, Virginia
Year: 1991
Model: Cherokee
Engine: I-6 4.0 HO
Yes - and that's usually how the smog "techs" out here function-test the thing (disconnect the vacuum, hook up a hand pump, and pull a vacuum. Should stall out the engine, and should hold vacuum for 30 seconds or so.)
However, I think the EGR is a stupid solution to a known issue - and I can think of a couple of better ways to do it.
EGR = "Exhaust Gas Recirculation" - what you're doing is running exhaust gas back into the engine to "cool off" combustion (how you can cool off a heat reaction by introducing 1000*F exhaust gas escapes me...)
The problem with EGR? Mainly, it's introducing another failure-prone component into the system, complete with its own activation system, and exhaust gas always carries particulate carbon with it - so you're not only running hot exhaust gas back into the intake stream (and screwing up air temperatures,) but you're also coating the inside of your intake with carbon (which ends up mandating parts replacement - even though the part itself hasn't failed, it's just irretrievably coated with carbon, which either clogs up the sensing element or coats it with an insulating layer. Both bad.)
I'd even argue the merit of having it on our (relatively) low-compression engines - I've got before/after smog reports somewhere on my 87. The first test was with a failed EGR - it otherwise passed on all elements (including NOx.)
The second test was after I'd replaced the EGR - NOx unchanged, HC and CO and skyrocketed to "barely passing."
Go figure.
However, I think the EGR is a stupid solution to a known issue - and I can think of a couple of better ways to do it.
EGR = "Exhaust Gas Recirculation" - what you're doing is running exhaust gas back into the engine to "cool off" combustion (how you can cool off a heat reaction by introducing 1000*F exhaust gas escapes me...)
The problem with EGR? Mainly, it's introducing another failure-prone component into the system, complete with its own activation system, and exhaust gas always carries particulate carbon with it - so you're not only running hot exhaust gas back into the intake stream (and screwing up air temperatures,) but you're also coating the inside of your intake with carbon (which ends up mandating parts replacement - even though the part itself hasn't failed, it's just irretrievably coated with carbon, which either clogs up the sensing element or coats it with an insulating layer. Both bad.)
I'd even argue the merit of having it on our (relatively) low-compression engines - I've got before/after smog reports somewhere on my 87. The first test was with a failed EGR - it otherwise passed on all elements (including NOx.)
The second test was after I'd replaced the EGR - NOx unchanged, HC and CO and skyrocketed to "barely passing."
Go figure.
5-90, didn't you know? Ancient Chinese Secret!
All jokes aside, and not meaning to hijack a thread, but I've also seen many of your responses on EGR related threads, and on one particular one you mentioned the use of a Water/Methanol fogger to further enhance performance, efficiency, and clean burning of an engine. From my research, these usually come better into play with forced induction engines and also diesels, but can they play any benefit on a naturally aspirated gas engine? Such as our humble 4.0, or maybe even on a bigger powerhouse like a 5.7 V8?
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