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Discussion Starter #1
'ello..

EGR (exhaust gas recirc) what's all that about then? I guess it's some sort of emissions control, but any of you more spanner handy guys fancy explaining how it's supposed to work? :)

Cheers,
A
 
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The EGR device takes a certain part of the exhaust gases ot out the exhaust manifold, back into the inlet manifold. I suspect this happens only under certain conditions, as there is an EGR valve. Perhaps during cold starts, to warm up engine quicker? I see that the later 155 2L 16v don't have this device anymore, so it probably wasn't really worth it. Plus there was the downside of extra complication and reliability. My EGR valve failed a few weeks ago. (Cost about the same as a variator to replace.)
 
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If I remember correctly, EGR reduces emission of nitrous oxides (NOx). By adding a little exhaust gas to the air/fuel mixture, the flame speed is reduced. On ignition, the flame front advances from the spark outwards. Diluting the mixture slows the flame front down, which in turn reduces peak temperatures. As NOx are formed at very high temperatures only, reducing the flame temperature reduces the formation of NOx, making our cars a little more furry animal-friendly. Apparently, it doesn't affect performance (much).
 
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