The CR diesel refers to a series of motors that includes 4, 6, 8 and 12 cylinder engines. CR means Common Rail, and the term refers to the common fuel rail that feeds the injectors. And there are many other changes that set this series of engines apart from their earlier cousins. They have lighter crankshafts with two counter rotating balance shafts. The two camshafts are interconnected with a high tech gear system that eliminates backlash and vibration. The valves are operated by small roller rockers, with stationary hydraulic lifters, thus reducing reciprocating mass in the valve train. A complicated intake manifold has flaps driven by a motor that controls the air flow through one intake tract for each cylinder. The other intake tract is always open. Perfect intake air swirl characteristics result, which improves fuel atomization and combustion. The pistons are have an improved design to match up with the intake swirl as well as cool better due to an internal oil passage. There is an improved valve cover with a pressure control valve to match the intake vacuum. Each valve cover incorporates two flutter valves, four cyclonic chambers, and a final damping chamber to separate oil from crankcase vapors, reducing oil consumption.
The term Common Rail, or CR, refers to the high pressure fuel rail that feeds each injector, varying from 8000 to 27,000 psi as needed. The piezoelectric injectors have a multiple wave electronic injection control signal, and are extremely precisely controllable. Like the PD design, an electric fuel pump in the tank pushes the fuel to the engine. A second auxiliary pump mounted just before the high pressure pump keeps an adequate fuel volume available. A high pressure fuel pump driven by the timing belt raises the fuel pressure all the way to injection pressure. A radical change in glow plug technology includes a pressure sensor in each glow plug that monitors the cylinder compression. The engine control unit monitors the rising compression and precisely controls the timing and duration of the injection using several electric pulses to achieve a maximum burn ratio. The injection event is covered in about 1/3 of a millisecond when the engine is at redline, or its maximum rpm. Time to start talking in microseconds when referring to the individual pulses. And we are talking a level of precision not seen before in any automotive engine.
Diesel Emissions Control for the CR Diesel
A short version of the CR diesel emissions control system should mention the diesel particulate filter (DPF) and the regeneration cycles to keep it clean. The DPF captures soot and later burns it down into ash, which is stored during the life of the vehicle or filter. The engine computer monitors the soot loading of the DPF and initiates active regeneration cycles periodically to make sure it does not clog with soot. If your diesel particulate filter indicator light on the dash comes on, the filter is getting clogged, and you must take a higher speed drive to clean it out. If the light stays on and the glow plug light comes on, the dash display will indicate “Check Engine – Service Shop”. At that point you MUST see us at Karmakanix or go to a dealership. If you just keep driving, the DPF will have to be replaced.
A CR Tdi MUST Use 507.00 Oil ONLY
One simply absolutely MUST use 507.00 rated oil in a CR Tdi motor. If you have your oil changed anywhere besides Karmakanix or a dealership, ask to see the bottle. It must have the 507.00 rating written on it somewhere. Some online sources would lead you to believe that 507.00 just means it can go 10,000 miles. Not true! Firstly, it should no oil should be allowed to stay in any motor for 10,000 miles. See our oil change page for more info. Secondly, The 507.00 is essential in a CR Tdi to prevent engine failure and possible damage to the emissions system.
During active regeneration of the diesel particulate filter, the unburned fuel that warms up the exhaust also contaminates the engine oil. 507.00 oil allows these contaminates to evaporate out. Other earlier versions of diesel oil do not, and the contaminants will eventually cause engine failure, usually cylinder wall or cam and lifter damage. The damage can be monitored using a measuring value block that shows the current compression in each cylinder. 507.00 rated oil also has a very low ash content, and does not add significantly to the soot load of the diesel particulate filter.
Biodiesel Usage in CR Engines
There is a trade off, and the Germans are not happy. You cannot run biodiesel in these engines. Here’s why: Biodiesel has a much higher temperature of evaporation than regular diesel. biodiesel will not evaporate out of the engine oil after an active regeneration cycle. At Karmakanix, we have seen other problems with CR engines that were run on biodiesel. One had a high soot load because the regeneration cycle was not working correctly. The pressure sensor for the DPF had failed. Whether that related to the biodiesel usage or not, we do not know. We sympathize with biodiesel customers, and understand that they rightfully want to help save the planet. And dealers were known to frown on biodiesel usage in all past models and engines as well. In the case of the CR diesel, we must side with the dealer policy as the issues and technological reasons are clear. If we could remove the DPF from the system, biodiesel usage would not be a problem.
Karmakanix would like to advise patience. The 10% to 15% better mileage without DPF regeneration cycles should animate manufacturers to help meet stricter CAFE standards on fleet average mileage. Germans love biodiesel, as it should be. Some German engineers are no doubt working on the next emissions control system that could eliminate the diesel particulate filter, and the resultant oil contamination due to the regeneration cycles. We of course have no idea what that could be. Soot eating Nanites or high temperature bacteria? Laser guided soot molecule destruction? Better living through science.
DPF Removal: the California Bozo NoNo
In California, we cannot remove the DPF any more than we can remove the catalytic converter from a gasoline vehicle. The vehicle will NEVER legally pass a smog test. The penalties levied on the shop that removes a Diesel Particulate Filter are fines from $25,000 to $250,000 per incidence, and 6 months to 2 years jail time. The same goes for any smog station that fudges one through smog. Karmakanix will not risk that! Some other unnamed states are either more lenient or do not check. The engine control unit must be reprogrammed to remove the active regeneration cycles, and to ignore the DPF pressure sensor, and modify the interpretation of the oxygen sensors and the EGR temperature sensors signals. Or else a huge cloud of raw diesel smoke blows out of the tailpipe when a regeneration cycle occurs.
Modifying or tampering with any emission control system is also a federal crime, as per EPA regulations. The Feds have not clamped down on anyone except some of the manufacturers of the pipes that replace a DPF when removed. Some have been prosecuted for selling these pipes to customers in states like California. That may change. Likely it will not.
The Total Failure Mode: CR Diesel Fuel System Replacement
It is extremely important to know about the possibility of total system failure in a CR Tdi diesel. Somehow your engine goes from running perfectly to a dead fuel system full of metal flakes. This rare (so far) problem stops your journey, and will cost you your life savings if you have to pay for it.