Quote:
Originally Posted by julesbass
This is admittedly about a Ford Galaxy 1.9Tdi, but I wonder if this would apply to 75 ZT owners who have disabled their EGR or fitted a bypass.
"On TDIs, EGR valve should open to allow carbon dioxide, which acts as a cooling gas) into the combustion chambers when the engine is under load (>30% boost). This allows the combustion chamber temperature to drop and thus the temperature of the exhaust gases. If it sticks in the closed position the exhaust gas temperature will rise causing a) the turbo bearings to fail and b) engine oil into the induction system. This can cause the engine to run on its crankcase oil until it is either stalled or goes bang. Problems with EGR valves in TDI engines are often the cause of rough running when the valve is stuck in the open position as well. In several cases turbos have blown but the EGR valve has not been replaced. Inevitably the new turbo unit will not last long."
Come on technical bods, lets have some more clarification on this subject!
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There are some very valid points there if taken in the context of VW Group (as fitted in Galaxy TDi) and Renault diesel engines. Both the VW and Renault 1.9 TDi family of engines are very sensitive to blocked EGR systems. Lagunas and Meganes with the 1.9 and 1.5 DCi engines have a failure rate that would make you think they were fitted with chocolate turbos. But in truth, it is not the EGR system, or lack of one in the case of a bypass being fitted that is to blame. It is more a case of the inherent lack of long-term reliability and low operating tolerances of the particular breed of Garrett VNT turbo that is fitted to these engines.
The M47(R) engine is not hamstrung by this problem. Our Mistsubishi Industries turbo is as reliable as they come. I can recall many instances of 320d's, Lagunas, Golfs and Passats suffering from turbo failure. The Laguna in particular commonly consumes its engine oil through the turbine seals on an expired turbo leading to complete destruction of the engine. I have not heard of a single instance of turbo failure on a 75 or ZT. They have undoubtedly occurred but it certainly can't be considered a common or even infrequent problem.
In my opinion, the design and components of the 75/ZT diesel intake and exhaust system are of sufficient quality and reliability that bypassing the EGR has no detrimental effect to reliability whatsoever. The 320d may have had 150bhp as standard but they are known to be far less reliable as a consequence of the turbo fitted to generate that extra 15bhp.
Mod away fellas!!!