Not to worry, I got it wrong the first time too. IMHO, it would be better to route the exhaust from after the catalytic converters but it is actually coming from the exhaust manifold before the catalytic converters: You can count the four exhaust pipes the merge into a single pipe to feed the exhaust pipe but there is a fifth pipe that reaches up to the "cooled EGR" unit. The catalytic converters are very efficient at taking out hydrocarbon compounds that condense on cooled surfaces. So it makes sense to tap the exhaust gas after the catalytic converters when over 90% of the HCs will be gone. Then the longer pipe can route up to the existing cooled EGR and help further cool the exhaust. The traditional problem with EGR is coking up the heat riser tubes back in the 1970s. They were brilliant until condensed HC plugged them up. This is the risk I'm concerned about. Bob Wilson
Ok, we had the technologies confused. I was thinking heat recovery. I, too, would like to see the EGR later down the pipe, but I suppose back pressure is increased w/ longer pipes, and you'd lose some of the efficiency?
The idea is that the exhaust gas is inert - no remaining oxygen. After the cat, NOx is converted back to N2 + O2 although some oxygen goes into burning HC and converting CO to CO2. More oxygen in the exhaust gas would reduce the effectiveness of EGR.
