I currently have a 4 cyl sprinter on order. I plan to own this a long time, and want to understand the systems to know what is normal, and to keep on top of any issues.
My current car is a 2009 VW Jetta TDI wagon. (so some of my understanding of emissions treatment will not directly apply to sprinters)
http://www.natef.org/NATEF/media/NATEFMedia/VW Files/2-0-TDI-SSP.pdf
provides a good overview of the VW engine in my car. would be wonderful if a similar document could be found for the 4 cyl in the current Sprinters sold in US.
There are a couple challenges diesels have emissions wise.
The diesel exhaust smell the old among us grew up with (and I thought was nice as a kid, since it was associated with trips to the big city) comes mostly from unburnt hydrocarbons, and particulates.
These are dealt with in a couple ways. Frst, modern injectors allow very precise metering of fuel, and timing which allows very close control of how much fuel is injected when in the combustion cycle of each piston/cylinder. With fuel under control, air is also controlled by valves to restrict the intake diameter as needed, and turbocharger controls. which change the pressure, which translates into more air to combine with injected fuel, and more power from the same size engine block.
An oxidizing catalyst enables oxidation (burning) of the smelly parts of the exhaust, and a diesel particulate filter(DPF) captures the sooty particulate parts. The DPF captures soot particles and has a catalyst which enables conversion (by more oxidation) of the carbon into mostly carbon dioxide and water. This regeneration happens passively when the exhaust temperature is high enough. But just driving is not enough to process all the captured soot.
Programs in the engine control computer maintain estimates of the soot levels, and when they are high enough, the computer runs an active DPF regeneration cycle. Operating parameters are modified (by control of fuel and air to achieve required conditions in the exhaust system to process the captured soot into mostly CO2 and H2O) These programs also include diagnostics and will tell the driver when the designers think action is required, and log errors for technicians to use in isolating problems which require action.
Diesels are operated mostly in lean conditions (more air than needed to burn the fuel.) An invisible pollutant is generated which needs to be treated. 78% of air is Nitrogen gas which will, under the high heat inside the engine, combine with the oxygen in the engine to generate oxides of nitrogen (NOx). To limit this problem, exhaust gasses are recirculated into the intake, which reduces the extra oxygen in the combustion chamber.
Residual NOx needs to be treated. In my VW, extra fuel is used to react with captured NOX. in the Sprinter, Diesel Exhaust Fluid DEF) is used to treat the exhaust, removing the extra O from those nasty NOx molecules.
All these systems do a dance around each other, and when everything is working, life is good, good power is available to move the van down the road, good economy, High MPG and much cleaner air is preserved for those of us that breath it.
But a variety of sensors and control devices all have to work. When these go bad, it can get expensive. Trying to guess the problem is more expensive. There are a variety of skill levels in mechanics, so some will be able to make a minimal cost repair, and some will not. The computer runs diagnostics on most of the components, and monitors system behavior. Logs of error conditions noted are kept for later review by a technician who has a capable scan tool or system. In some cases, the computer will notify the driver by lighting up parts of the instrument panel, and by audio warnings.
Sorry for the long post, but I would like to hear more about how these systems work, how to verify they do work, and how to detect when things go wrong, and how to fix what goes wrong.
My current car is a 2009 VW Jetta TDI wagon. (so some of my understanding of emissions treatment will not directly apply to sprinters)
http://www.natef.org/NATEF/media/NATEFMedia/VW Files/2-0-TDI-SSP.pdf
provides a good overview of the VW engine in my car. would be wonderful if a similar document could be found for the 4 cyl in the current Sprinters sold in US.
There are a couple challenges diesels have emissions wise.
The diesel exhaust smell the old among us grew up with (and I thought was nice as a kid, since it was associated with trips to the big city) comes mostly from unburnt hydrocarbons, and particulates.
These are dealt with in a couple ways. Frst, modern injectors allow very precise metering of fuel, and timing which allows very close control of how much fuel is injected when in the combustion cycle of each piston/cylinder. With fuel under control, air is also controlled by valves to restrict the intake diameter as needed, and turbocharger controls. which change the pressure, which translates into more air to combine with injected fuel, and more power from the same size engine block.
An oxidizing catalyst enables oxidation (burning) of the smelly parts of the exhaust, and a diesel particulate filter(DPF) captures the sooty particulate parts. The DPF captures soot particles and has a catalyst which enables conversion (by more oxidation) of the carbon into mostly carbon dioxide and water. This regeneration happens passively when the exhaust temperature is high enough. But just driving is not enough to process all the captured soot.
Programs in the engine control computer maintain estimates of the soot levels, and when they are high enough, the computer runs an active DPF regeneration cycle. Operating parameters are modified (by control of fuel and air to achieve required conditions in the exhaust system to process the captured soot into mostly CO2 and H2O) These programs also include diagnostics and will tell the driver when the designers think action is required, and log errors for technicians to use in isolating problems which require action.
Diesels are operated mostly in lean conditions (more air than needed to burn the fuel.) An invisible pollutant is generated which needs to be treated. 78% of air is Nitrogen gas which will, under the high heat inside the engine, combine with the oxygen in the engine to generate oxides of nitrogen (NOx). To limit this problem, exhaust gasses are recirculated into the intake, which reduces the extra oxygen in the combustion chamber.
Residual NOx needs to be treated. In my VW, extra fuel is used to react with captured NOX. in the Sprinter, Diesel Exhaust Fluid DEF) is used to treat the exhaust, removing the extra O from those nasty NOx molecules.
All these systems do a dance around each other, and when everything is working, life is good, good power is available to move the van down the road, good economy, High MPG and much cleaner air is preserved for those of us that breath it.
But a variety of sensors and control devices all have to work. When these go bad, it can get expensive. Trying to guess the problem is more expensive. There are a variety of skill levels in mechanics, so some will be able to make a minimal cost repair, and some will not. The computer runs diagnostics on most of the components, and monitors system behavior. Logs of error conditions noted are kept for later review by a technician who has a capable scan tool or system. In some cases, the computer will notify the driver by lighting up parts of the instrument panel, and by audio warnings.
Sorry for the long post, but I would like to hear more about how these systems work, how to verify they do work, and how to detect when things go wrong, and how to fix what goes wrong.
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