Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[davethediver]

As per the title so everyone knows what the post is about   .

What exactly does it do? (in Laymans please)
Advantages and disadvantages of removing it and if you've done yours why?

Thanks Dave

[charlie]

Its a valve that controls how much(if any)exhaust gas(the stuff that comes out if the tail pipe)goes into the air intake to keep them emissions down and to help keep the combustion temp down

[cem_devecioglu]

its there to reduce the nox mixture (recirculating the exhaust gas drops the combustion temperature and the nox as a result) from the exhaust gases..nox is not measured in mot so useless..

if you disable it your engine power will very slightly increase..

[2woody]

there are various noxious gasses emitted into the atmosphere through your tailpipe.

Out of those, Nitrous di-oxide is the one that causes smog

research in the seventies showed that NOX is created at the higher combustion temperatures within hte engine, but this could be mitigated by feeding some exhaust back into the burning process ( hence EGR - Exhaust Gas Recirculation )

the valve recirculates some exhaust at critical times in the EU drive-cycle that is used to measure the emissions for new cars - a test that is way more complicated than the MOT - indeed the MOT doesn't even measure NOX.

So - removing an EGR valve makes no difference to everyday running, and won't affect the MOT. You do still need to have the valve plugged in to the electrics or your fuel injection will throw a wobbly.

( throw a wobbly is technical-speak for illuminating the "engine-death" light because it thinks the valve is no longer working )

[Kneepad]

I understand what the egr valve does. What I don't understand is how replacing cooled air from the turbocharger with hot exhaust gas can reduce combustion temperature.

Is it because there is less oxygen in the exhaust gas ?

I think I've just answered my own question.

[TheBoy]

Correct, the gas thats recirc'd via egr is inert.  Later DBW engines get around the need for EGR by lowering compression ratio, which apparently lowers combustion temp, thus less NOX formed.


Diesels, as I understand, use massive amounts of egr at cruising to help with economy - EGR can also have the effect of reducing cc of engine.