DirtyUltra

Hi Steve, I'm not looking to debate, nor am I looking to modify. Just interested in your statements about this engines downgrading on materials selection due to E6 subsystems being applied allowing for lower operating combustion temps (and any inherent risks therefore from adapting the original intended use case). So far I have not seen/read of anything other than conjecture. Still genuinely interested to see some technical information that supports your theories though, if you have it? Regarding PCV and oil mist. VAG revised the PCV and included an Air/Oil separator although that should be seen as a maintenance item.

Thanks Steve, I appreciate your time to explain the fundamentals but I understand the operation of EGR, DPF, AB and associated systems, NOx et al. Amongst other things professionally, I hold AAE through the IMI and have worked in the industry at various different roles and levels of contact. What I'm particularly keen to know is what I've quoted above, the source or technical data to support the downgrade of metal composition in order to reflect lower target operating temperatures, failure rate of turbos based on higher combustion temps? I will look up the posts/user you mention but as I understand it removal of EGR/DPF/AB should not create unmanageable combustion temps if the recalibration is correct and sub-systems are working. Turbo- As all EGR gas is directed into the engine via the turbo compressor, and this air load is at a higher temp than the outside air temp, then removal will not give an additional heat load on the compressor side. Effectively the EGR will follow the solenoid valve V339 closed flow state which does not put risk on the compressor. Turbine side will be effected by combustion temps (will comment separately) and turbine back pressure set by downstream back pressure(s). This would be DPF soot loading state, EGR cooler flow state and J88 exhaust door control state which comes off the DPF. This would need to be mapped open. DPF regen functionality maintained or DPF core removed. A fixed close state of the EGR V339, similar to the EGR cooler being blocked would increase pressure at the DPF and seen by the turbo. Which is why correct removal of the DPF backpressure is required, be it through maintenance or physical modification. Removal of AB would not change turbo operating environments other than as mentioned with combustion chamber temps. Back pressure from Oxi Cat would remain consistent. Combustion temps- the engine has three partial coolant circuits to ensure heat distribution is based on demand. This takes into account the engine, trans (if auto) and interior heating demands. Removal of EGR cooler feature will have adverse effect on engine warm up time and increase initial engine friction and wear rate, mpg etc. I'd say that's an almost negligible value though. However part of the warm up cycle is via static coolant flow, the pump is commanded off (no flow to EGR cooler or cylinder head) so whilst EGR will not warm a cold engine anymore, the cooling system is perfectly capable of rapidly warming engine via closed thermostat and static coolant flow conditions. Of the three coolant circuits, the micro-circuit runs around the cylinder head and around the combustion chamber (nearest valve seats). This circuit is off during warm up with flow directed through the heater matrix for fast cabin warm-up. The V488 coolant support pump is controlled by the ECM to directly manage the cyl head temps. Again even if load or speed (rpm) is in a high state, V488 is on constantly. The high temp circuit is run/controlled via the stat and radiator. The charge air cooler will manage intake temps (after the EGR/AB is added). It's efficiency is vitally important and they are often found to be gummed/carbonned up thanks to EGR. V188 charge air pump controls coolant to the charge cooler based on manifold temps. The pump can be off/ cycled/cont on depending on charge air temp vs target. A wise re-calibration will adjust these values! Pre and post temp sensors are used. General fuelling takes into account EGR position from G466 and three EGT sensors. Exhaust gas temp is the ultimate limiting factor of the turbos turbine and this value is managed by the ECM. Oil temp G266 sensing and various intake temps including the charge cooler all contribute to controlling combustion chamber temp. Lets also not forget the N75 wastegate control (VNT between high flow and steep working angle/no boost) which will ultimately dump off any pressure (heat) between the cylinders and turbine. Summary- if a recalibration is done correctly (as opposed to just removing duty cycles or DTC activation errors from memory) then their should be no risk to the mechanicals. Removing EGR will reduce some spool rates though as it retains the entire exhaust mass flow in front of the turbocharger turbine. The turbocharger responds better, particularly under part-load. This allows for higher charge pressures with it in situ. I have written this whilst working and have not proofed it. Apologies for any typos/ nonsensical ramblings...

Morning Steve, This sounds logical. Do you have any empirical proof though? Know of multiple people who have removed these systems then at x miles had heat related major component failures? Or know of the actual adjustments to the mix in terms of the CNHA construction methods and BOM compared to older units not relying on SCR/AB etc? Your theory makes sense but I would surmise those who "recalibrate" also have ultimate performance increased (boost/injector duration...therefore heat loading) and drive the car more aggressively. Thanks DU!