Drivbiwire
Zehntes Jahr der Veteran
- Joined
- Oct 13, 1998
- Location
- Boise, Idaho
- TDI
- 2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
The piston tops don't run hotter (maybe just a tad), the peak combustion pressure is simply higher. The higher pressure results in more complete combustion and this adds to the overall temperature in the combustion bowl (thus the increase in NOx).
Combustion occurs almost entirely in the bowl, if combustion is occurring so late as to expose the top of the piston to the actual flame front...you crack the piston or at the very least melt it.
This typically occurs with incorrectly mounted nozzles and incorrect sequencing of the injectors. Compound this with small nozzles (slower injection) and high performance tuning and the risk factors are pointing in the direction of a failure.
What I have found is that advancing timing insures that combustion occurs entirely in the combustion bowl. This insures that the ideal mixing of the fuel and air occur completely and in a controlled region designed for the stresses involved. Also the piston is cooled with oil so this further insures the margins required for safe operation of the motor at higher engine output or the slightly increased pressures more advanced injection timing settings result in.
Again I am purely of the opinion that combustion needs to be as complete as possible with the energy of the fuel being expended to drive the piston and insure the cleanest possible emissions. NOx may be higher with advanced timing but the reduction in PM goes a lot farther in terms of public perception of the diesel engine overall.
FWIW, we have tested TDI engines with all the NOx devices (EGR, Advanced timing) etc disconnected and found that the cars STILL meet all the emissions requirement...FWIW.
The funny part is that a gasoline engine put out more NOx than the TDI did, and this is with all NOx reduction devices inhibited on the TDI motor.
To sum it up, set the engine for best efficiency, lowest thermal stress on the downstream components (Turbo) and run with the least amount of soot particles generated that is possible for your specific configuration.
I only suggest:
-Advancing timing to the top of the range (mechanically) read by VCDS in basic settings mode
-IQ adjustement as needed to produce a light haze and no black smoke.
Do those two things and your engine regardless of tune, injector combination will be running at the top of it's game without impacting it's design life.
Combustion occurs almost entirely in the bowl, if combustion is occurring so late as to expose the top of the piston to the actual flame front...you crack the piston or at the very least melt it.
This typically occurs with incorrectly mounted nozzles and incorrect sequencing of the injectors. Compound this with small nozzles (slower injection) and high performance tuning and the risk factors are pointing in the direction of a failure.
What I have found is that advancing timing insures that combustion occurs entirely in the combustion bowl. This insures that the ideal mixing of the fuel and air occur completely and in a controlled region designed for the stresses involved. Also the piston is cooled with oil so this further insures the margins required for safe operation of the motor at higher engine output or the slightly increased pressures more advanced injection timing settings result in.
Again I am purely of the opinion that combustion needs to be as complete as possible with the energy of the fuel being expended to drive the piston and insure the cleanest possible emissions. NOx may be higher with advanced timing but the reduction in PM goes a lot farther in terms of public perception of the diesel engine overall.
FWIW, we have tested TDI engines with all the NOx devices (EGR, Advanced timing) etc disconnected and found that the cars STILL meet all the emissions requirement...FWIW.
The funny part is that a gasoline engine put out more NOx than the TDI did, and this is with all NOx reduction devices inhibited on the TDI motor.
To sum it up, set the engine for best efficiency, lowest thermal stress on the downstream components (Turbo) and run with the least amount of soot particles generated that is possible for your specific configuration.
I only suggest:
-Advancing timing to the top of the range (mechanically) read by VCDS in basic settings mode
-IQ adjustement as needed to produce a light haze and no black smoke.
Do those two things and your engine regardless of tune, injector combination will be running at the top of it's game without impacting it's design life.
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