GBMUD Posted April 22, 2009 Share Posted April 22, 2009 I removed the EGR valve yesterday, but I am puzzled as to what it does and when. Obviously I know it allows exhaust gas into the inlet manifold, but when? Under what conditions? And what does that actually achieve? The exhaust valve is controlled by the big diaphragm on the top. There is also a butterfly in the unit, controlled by the smaller diaphragm on the side of the unit. This appears to default open, so when does it close and why? What does it do for me? Both valves are apparently operated by vacuum. Thanks Chris Quote Link to comment Share on other sites More sharing options...
TomG Posted April 22, 2009 Share Posted April 22, 2009 As far as i understand it's to control NOx emissions (NOx isn't tested as part of MOT on diesels) i think the valve closes (recirculates) on cruise and hot idle. It's open (no recirculation) on acceleration & full throttle so no difference to performance. EGRs have been known to clog up the inlet manifold with soot http://en.wikipedia.org/wiki/Exhaust_gas_recirculation Quote Link to comment Share on other sites More sharing options...
Anderzander Posted April 22, 2009 Share Posted April 22, 2009 I don't know the conditions - but essentially they are to reduce emissions. Always seems to make a mockery of having an intercooler to me. Quote Link to comment Share on other sites More sharing options...
Matt Neale Posted April 22, 2009 Share Posted April 22, 2009 Chris, Google is your friend here: EGR Valve 1 EGR valve 2 EGR Valve on Wikipedia Matt Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted April 22, 2009 Share Posted April 22, 2009 NOx emissions form at high temperatures in the engine. Advancing the injection gives higher temperatures, higher pressures and better efficiency. Exhaust gas has (among other interesting properties) a high specific heat capacity, but it displaces the fresh air charge in the cylinder, so the EGR valve opens under part-load operation to allow the engine to run more advance than it would otherwise be able to without producing high NOx emissions. Disconnect it... Quote Link to comment Share on other sites More sharing options...
Les Henson Posted April 22, 2009 Share Posted April 22, 2009 Just what does this bad boy do? Fail. Les Quote Link to comment Share on other sites More sharing options...
BogMonster Posted April 22, 2009 Share Posted April 22, 2009 What Les said ^^ Dump it - its not even fitted to later Td5 ROW vehicles. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted April 22, 2009 Author Share Posted April 22, 2009 It is already dumped, I was curious to know more about it. I am still in the dark as regards the butterfly valve, does this serve some function other than the EGR valve? Or is it simply a means of restricting the availability of fresh air to promote use of exhaust gasses? Without the EGR present the turbo seems to come on boost sooner/from lower revs. I was not expecting that to happen so I am happy that it is not just in my mind. Chris Quote Link to comment Share on other sites More sharing options...
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