EGR system layout, function, and importance?
07-20-2018, 08:22 PM
#1
Three Wheelin'
Thread Starter
EGR system layout, function, and importance?
browsing the PET and WSM and not clear about the EGR system. is the air injection system (with air pump) the main component(s)
of the EGR? not sure I understand its usage and importance? what is the relationship with the crankcase ventilation?
can someone provide an overview?
of the EGR? not sure I understand its usage and importance? what is the relationship with the crankcase ventilation?
can someone provide an overview?
07-20-2018, 09:31 PM
#2
Archive Gatekeeper
Rennlist Member
Rennlist Member
Have a look at the 1987 Service Info book (you do have the Morehouse CDs, yes?) , pp 1-13 and 1-14. EGR has almost nothing to do with crankcase ventilation, beyond manifold vacuum keeping the diverter valve open and flowing air either to the exhaust ports or the posterior third of the cats.
Setup for no-cats:
Setup for cars with cats:
Setup for no-cats:
Setup for cars with cats:
07-21-2018, 11:18 AM
#4
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
The later system is a lot closer to AIR (Air Injection Reaction) than to EGR (Exhaust Gas Recirculation). EGR systems allow a certain amount of exhaust gas to dilute the intake charge to reduce the effective compression ratio and cool the combustion for NOx control. As Rob points out, the AIR system for non-cat cars injects fresh air into the exhaust gas flow immediately downstream of the exhaust valve. Intent is to offer oxygen to a possibly hydrocarbon-rich exhaust so that the combustion cycle can complete before the gasses cool off.. No exhaust gas is recirculated.
On catalyst cars, the air pump adds oxygen to the CO catalyst to make CO2. There's some cooling too, but it's an almost unwanted byproduct as the CO cat needs to be at temperature to "light off".
On catalyst cars, the air pump adds oxygen to the CO catalyst to make CO2. There's some cooling too, but it's an almost unwanted byproduct as the CO cat needs to be at temperature to "light off".
07-21-2018, 11:38 AM
#6
Three Wheelin'
Thread Starter
The later system is a lot closer to AIR (Air Injection Reaction) than to EGR (Exhaust Gas Recirculation). EGR systems allow a certain amount of exhaust gas to dilute the intake charge to reduce the effective compression ratio and cool the combustion for NOx control. As Rob points out, the AIR system for non-cat cars injects fresh air into the exhaust gas flow immediately downstream of the exhaust valve. Intent is to offer oxygen to a possibly hydrocarbon-rich exhaust so that the combustion cycle can complete before the gasses cool off.. No exhaust gas is recirculated.
On catalyst cars, the air pump adds oxygen to the CO catalyst to make CO2. There's some cooling too, but it's an almost unwanted byproduct as the CO cat needs to be at temperature to "light off".
On catalyst cars, the air pump adds oxygen to the CO catalyst to make CO2. There's some cooling too, but it's an almost unwanted byproduct as the CO cat needs to be at temperature to "light off".
No. just reduce emissions.