Ok...I know the CRD has just hit the streets so there aren't many of them around and probably none that have a fair number of miles on them (20K+) but something is on my mind.
Anyone wonder if the Liberty CRD intake will be likely to clog with sludge like the VW TDI?
I'm asking because it's a well documented issue over at http://www.tdiclub.com
and by VW...do a search on the tdiclub site for CCV or intake clogging and you'll see what I'm talking about. I’m no vehicle guru or engineer, but from everything that I’ve read it's caused by the combination of an EGR valve (which the Liberty CRD and the VW TDI have) and a PCV valve (or CCV, Crank Case Ventilation valve). As I understand it, it goes something like this: PCV valve vents air into the intake stream (after the air filter and before the turbo) that has a bit of oil & crankcase gasses in it. EGR directs exhaust gasses (containing some soot because it hasn’t hit the catalytic converter yet) back into the intake stream whenever lean conditions occur...it does this because lean conditions create NOX (don’t ask me why but I think it has something to do with the high cylinder temps caused by lean conditions), the catalytic converter can't burn off the NOX because US diesel fuel contains too much sulfur, and the sulfur would destroy a gas-engine style 3-way cat (using a 2-way cat that isn't designed to burn off NOX is my understanding of what’s used in US diesels). Apparently EGR helps cool the cylinders enough to help prevent excess NOX from being formed, so that's why the EGR valve is there...to help reduce NOX so the vehicle can meet emissions requirements. Anyway, apparently the combination of the soot from EGR and the oil from the PCV mix and form a sludge that sticks to the intake manifold walls and intercoolers on the VW TDI. This stuff builds up over time and has to be cleaned out to restore power & efficiency. VW TDI owners are intimately familiar with this...some have to clean their intake manifolds & intercoolers every 20K-50K miles, others have never had an issue with it.
The thinking seems to be that if you eliminate or greatly reduce either the soot from EGR or the oil from PCV that the clogging problem is greatly reduced. Limiting EGR activity is not easy...some VW TDI owners simply disable the EGR valve and live with the check engine light, while others use software to limit EGR activity. And many VW TDI owners use a more robust filtering system between the PCV valve and the air intake like the one at http://www.reliableindustries.com/ca...NH/provent.php
to remove most of the oil from the equation.
It seems to me that the ingredients that create the clogging in the VW TDI are also present in the CRD. Low sulfur fuel seems to be the answer...low sulfur fuel (less than 15 ppm) would enable the use of a 3-way cat to kill the NOX and would likely eliminate the need for EGR or at least reduce EGR operation to a point where it wouldn't be an issue. It’s not really an issue on gas engines that use EGR…there’s far fewer particulates of soot in the exhaust of a gas engine, so by default one of the two ingredients to the sludge is mostly absent.
It's not a deal-breaking issue for me...even if I have to clean the manifolds now and then I still want a CRD. And who knows...maybe this won't be an issue for the Liberty CRD at all. After all, the injection system is different (injector pumps for the TDI and common rail for the CRD); the TDI is absolutely tuned for economy (lean mixtures requiring aggressive EGR activity), and the CRD doesn’t seem to be tuned for economy…VW TDI mileage is about 50% better than the gas 2.0, where CRD economy is only about 25% better than the gas 3.7, telling me that the CRD might run a little more rich than the TDI and it depends on the cat to clean up the exhaust more than the TDI…if it does, then EGR operation would be less than in the TDI due to reduced cylinder temps caused by more fuel being injected (if I assume that fuel acts as a coolant before it explodes). And the intercooler on the VW TDI may have something to do with it as well…cooling the mix of air, soot, and oil to a point where it can condense and stick to the walls of the intercooler and intake manifold…I’m not even sure if the CRD is intercooled or not (shows you my level of knowledge…LOL).
Thoughts? Please feel free to point out errors in my information, thinking, assumptions, etc…I’m here to learn just like everyone else.