Quote:
Originally Posted by BigfootBushy
Not trying to upset anyone but if there is no pollution benefit from EGR, why is it being fitted to heavy diesels to help them meet emission targets. I was under the impression that by using exhaust gas in the charge air was to give a more complete burn. There is also a lot of discussion within the truck industry about the increased cooling demands of EGR engines.
I am happy to be corrected if this is wrong
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Exhaust Gas in Inert meaning it gives no flamable benifit, does not assist with burn, just fills the combustion chamber with inert Gas which doesn't burn, lowering exhaust temps.
Secondary Injection assists with with removing any hydrocarbons which are not burnt in the combustion and make it through to the exhaust, introducing oxygen enriched air to the exhaust deals with this _ This is a cold start function to deal with enrichment of mixture in petrols.
EGR pollution control gives maybe 10% benifit to pollution control where as the Petrol EGR will have 100% for
eg. It's NOx which the EGR is designed to deal with, Which is an issue with high Exhaust temperatures introduced with running a leaner mixture (petrols)
It was orginally fitted for pollution control but later to find that it did not have the same outcome as with a petrol engine, however could be used to cool the Variable vane turbos.
Cools the turbo but heats up the cylinder head.. this is the cooling issue you refer to, and is an issue as seen with older Generation turbo diesels removing the EGR system decreased temperatures.
It's a fine line with diesel EGR, run without it you see the higher exhaust temps, run with it you run higher engine temps. Going to be more of an issue with the next generation of diesels just around the corner.
Can certainly see how they imposs issues with larger earth moving equipment.