EGR removal

[2088bob]

right now i am in the process of cleaning this engine up. Have just removed the EGR system and fabricated a tidy plate to cover the opening in the plenum .Is this a good idea, retaining the egr complicates headers fabrication what are your views on this

regards 2088bob

[EverWiser]

EGR valves were a fix applied back when most vehicles were carburated. They carried over to the early generation of EFI cars but I believe the EGR valve has gone the way of the dinosaur on most cars built in the last 8 or 10 years. If you do some good tuning, emissions-wise, I doubt you'll need it.

[MegaScott]

right now i am in the process of cleaning this engine up. Have just removed the EGR system and fabricated a tidy plate to cover the opening in the plenum .Is this a good idea, retaining the egr complicates headers fabrication what are your views on this

regards 2088bob

If you believe all the hype about EGR, it almost sounds like the holy grail, you hear stuff like "reduces Nox emmissions" and "increases fuel mileage" Yada Yada Yada.....No doubt the mileage part is true to some extent, you are introducing inert gas into the engine, and essentially replacing some of the air and fuel with it, this reduces the amount of Air/fuel you need to burn in order to acheave proper combustion. The newer cars have really sophisticated schemes to measure how much EGR is going into the engine, Megasquirt is not designed to use it, and the benifits are probably small, and only useful at very low load, so removing it will have no consequence as far as your buggy is concerned, unless you live in a smog zone, where the emissions equipment must be intact.(not!)

[efahl]

They carried over to the early generation of EFI cars but I believe the EGR valve has gone the way of the dinosaur on most cars built in the last 8 or 10 years.

On the contrary, I think you'd find it very difficult to find a new car that did not have EGR. It is a crucial player in lean burn technologies (see, for instance, the new Honda i-VTEC I motor, which uses large amounts of EGR to reduce pumping losses and lower NOx emissions when running at AFRs as lean as 65:1).

Eric

[baldur]

BMW don't have EGR solenoids on their latest engines with variable timing, they just use the variable valve timing to take care of EGR.

[danielbal]

Actually, EGR’s sole purpose is to reduce NOX emissions.  The way it does this is by reducing combustion temperatures.  NOX is only formed at high temps.  And yes, 95% of all cars certified for sale in the US still have them.  I am an ASE Master Tech and have my own shop and I haven’t seen a car without it in many years.  I am not so sure it increases fuel mileage however.  I always believed it hurt fuel mileage.  How does diluting the fuel and air charge with a non-combustible gas “reduce the amount of air and fuel required to achieve proper combustion?”  EGR reduces combustion temp and therefore it would seem to me that it robs the engine of a certain amount of power and efficiency.
 
Another thing to think about,  We troubleshoot poor and stumbling idle problems all the time.  About 1/3 of the time the trouble is a stuck open EGR valve.  They are only supposed to open at part throttle cruise and the engine will hardly idle if EGR is open.
 
This is also my first post, I’ve been lurking for a while.  I have a project coming up that I am gearing up for (Ford 460) and you guys who populate this forum are awesome at sharing your knowledge.  I have a lot more confidence that I can do the conversion after seeing the help I can get here.
 
Daniel Bal

Posted by email.

[MegaScott]

Actually, EGR’s sole purpose is to reduce NOX emissions.  The way it does this is by reducing combustion temperatures.  NOX is only formed at high temps.  And yes, 95% of all cars certified for sale in the US still have them.  I am an ASE Master Tech and have my own shop and I haven’t seen a car without it in many years.  I am not so sure it increases fuel mileage however.  I always believed it hurt fuel mileage.  How does diluting the fuel and air charge with a non-combustible gas “reduce the amount of air and fuel required to achieve proper combustion?”  EGR reduces combustion temp and therefore it would seem to me that it robs the engine of a certain amount of power and efficiency.

Snip, Snip
 
Daniel Bal

I guess a poor choice of words on my part, what EGR will do for mileage is to reduce the intake vacuum, therefore decrease pumping losses. Also the addition of EGR gas allows a leaner mixture without increasing the combustion temperatures of which will otherwise tend to increase NOx emissions. Does not the combination of these two give better fuel economy?

[efahl]

Does not the combination of these two give better fuel economy?

Well, with old school EGR I don't think the volume of effluent is sufficient to really help with fuel economy much, but with the newer lean-burn implementations that is specifically one of the engineering goals (and why Honda has been bragging up their 65:1 AFR). They aren't burning less fuel to produce the same total HP, but they are reducing pumping losses quite dramatically and thus putting more of that HP out the crankshaft (so either you go faster with the same fuel, or back off and go the same speed with less).

The big trick with such lean mixtures is to get the fire started, and that's where things like direct injection, stratified charge and proper chamber swirl come into play (I may have already said this on the other thread where we were talking about egr, sorry).

Eric

[Hans]

I don't know about my wife's 2001 Corvette, but I know my '94 Defender has no EGR valve and just passed emissions with absurdly clean numbers for an early 1960's engine design with a hack-job factory EFI. (IIRC 7ppm HC and 0.00% CO)

I also know that the Jeep 4.0 hasn't had an EGR vavle since 1990. I'm using this manifold on my CJ, but I haven't gotten it ready for an emissions inspection just yet.

-Hans