Ted_Grozier
Veteran Member
When Joe Rappa hooked up is portable emissions tester to my stock ECU TDI with 205 injectors, the amazingly low NOx surprised him. It was the lowest he had measured to date.
The reason is that the EGR map uses an injection quantity value that is calculated based on the stock 184 injectors.
Thus when installing 205s with a stock EGR and ECU you decrease available oxygen and reduce NOx below stock levels, with a corresponding increase in HC emissions --> then soot in the oil as some have observed.
Solution: adapt EGR to suit the 205s. How much? I do not know. But would like to run some tests. Ideally we would want to reduce EGR by 15-20% or so.
Amazing, all these years of diesel study going out the window. You get in the mindset that a diesel is always lean-burn, but on the TDI with electronic EGR there really is to some degree a "mixture" and a semi-closed control loop. (No oxygen sensor downstream but lots of feedback on the intake side; also calculated values.)
It's remarkable how all the systems interact.
The reason is that the EGR map uses an injection quantity value that is calculated based on the stock 184 injectors.
Thus when installing 205s with a stock EGR and ECU you decrease available oxygen and reduce NOx below stock levels, with a corresponding increase in HC emissions --> then soot in the oil as some have observed.
Solution: adapt EGR to suit the 205s. How much? I do not know. But would like to run some tests. Ideally we would want to reduce EGR by 15-20% or so.
Amazing, all these years of diesel study going out the window. You get in the mindset that a diesel is always lean-burn, but on the TDI with electronic EGR there really is to some degree a "mixture" and a semi-closed control loop. (No oxygen sensor downstream but lots of feedback on the intake side; also calculated values.)
It's remarkable how all the systems interact.