Ranger1 wrote:
I ran across a link in the TDI forum, posted back in 2004, where someone with a manual on the Bosch EDC-16 system described some of its operation. I wish I had seen this earlier. This is the same electronic engine control system that our CRD uses. The one feedback loop they describe that makes it extremely difficult to decrease EGR flow is an O2 sensor... the ECM (EDC-16) is adjusting fuel trim, and monitoring EGR flow by measuring oxygen content in the exhaust. They thought this measuring was occuring somewhere in the millisecond range - maybe hundreds of times per second. If that's true, and we have an O2 sensor feedback loop, it looks like EGR is here to stay on our CRD's.
I looked for a sensor in the CRD exhaust pipe, starting from the turbo exit all the way down to the muffler. I don't see anything. The only place I haven't looked at yet is the exhaust manifold, hidden by the heat shield for the turbo and other accessories. Has anyone seen any O2 sensors on their CRD exhaust system?
Link is here:
http://forums.tdiclub.com/showthread.ph ... tuning+box
Thanks as usual, Ranger1. Good information to have. I'm puzzled by one thing: in looking through the service manual, it is pretty clear that there is no O2 sensor on the CRD. How could it use the same ECM but not use an O2 sensor...did they just disable that part of the code?
The other thing is that I'm not sure what if any overall benefit there would be from just disabling the EGR, since I thought it only injected exhaust at low engine loads. Is that false?