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| Turbocharger power input (consumption) |
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| tautech:
--- Quote from: langwadt on March 27, 2020, 09:37:52 am --- --- Quote from: tautech on March 27, 2020, 09:14:39 am --- --- Quote from: langwadt on March 27, 2020, 09:05:37 am --- --- Quote from: tautech on March 27, 2020, 08:18:56 am --- --- Quote from: Circlotron on March 26, 2020, 01:09:20 am ---I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap. --- End quote --- Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns. --- End quote --- if efficiency was the only object maybe but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue --- End quote --- EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold. It uses a separate piped connection and valving to accomplish it. EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses. --- End quote --- yes EGR is the exact opposite. So why would it be and advantage to scavenge any remaining exhaust gasses only to add it back via the intake to meet emissions demand --- End quote --- Some don't give a damn about emissions ! :-DD |
| SilverSolder:
--- Quote from: langwadt on March 27, 2020, 09:37:52 am --- --- Quote from: tautech on March 27, 2020, 09:14:39 am --- --- Quote from: langwadt on March 27, 2020, 09:05:37 am --- --- Quote from: tautech on March 27, 2020, 08:18:56 am --- --- Quote from: Circlotron on March 26, 2020, 01:09:20 am ---I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap. --- End quote --- Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns. --- End quote --- if efficiency was the only object maybe but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue --- End quote --- EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold. It uses a separate piped connection and valving to accomplish it. EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses. --- End quote --- yes EGR is the exact opposite. So why would it be and advantage to scavenge any remaining exhaust gasses only to add it back via the intake to meet emissions demand --- End quote --- EGR can be disabled by the computer during peak demand input (mashing the pedal to the metal). The rest of the time, during normal driving, the emissions are then safely lowered with EGR without impacting performance. |
| tautech:
--- Quote from: SilverSolder on March 27, 2020, 04:27:00 pm --- --- Quote from: langwadt on March 27, 2020, 09:37:52 am --- --- Quote from: tautech on March 27, 2020, 09:14:39 am --- --- Quote from: langwadt on March 27, 2020, 09:05:37 am --- --- Quote from: tautech on March 27, 2020, 08:18:56 am --- --- Quote from: Circlotron on March 26, 2020, 01:09:20 am ---I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap. --- End quote --- Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns. --- End quote --- if efficiency was the only object maybe but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue --- End quote --- EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold. It uses a separate piped connection and valving to accomplish it. EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses. --- End quote --- yes EGR is the exact opposite. So why would it be and advantage to scavenge any remaining exhaust gasses only to add it back via the intake to meet emissions demand --- End quote --- EGR can be disabled by the computer during peak demand input (mashing the pedal to the metal). The rest of the time, during normal driving, the emissions are then safely lowered with EGR without impacting performance. --- End quote --- Little do you know of the negative effects on an engine of EGR in its attempt to mitigate emissions. Special oils had to be developed that better withstand the exhaust contaminants recycled through the engine that decimated ordinary diesel engine oil life and risked engine damage. There are many tricks to disable EGR that monitoring systems do not see. ;) |
| james_s:
EGR has benefits but it is certainly not without problems. It tends to really gum up intake manifolds, and I've had the EGR valves themselves get gummed up and stick. The crankcase vapor recovery also makes a mess of intakes, covering everything with hard black crust. |
| tautech:
--- Quote from: james_s on March 27, 2020, 06:43:20 pm ---EGR has benefits but it is certainly not without problems. It tends to really gum up intake manifolds, and I've had the EGR valves themselves get gummed up and stick. The crankcase vapor recovery also makes a mess of intakes, covering everything with hard black crust. --- End quote --- Another factor that further adds to intake gumming is the tiny oil leakage from turbo seals and when added to crankcase vapor and exhaust soot further exacerbates intake manifold deposits that in the longer term impact of motor performance by not letting it breathe properly. Modern advancements in EFI and common rail injection systems have much reduced the need for EGR based emission control. |
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