the EGR debate continues

Hi,

The EGR valve may do a few things... heating fuel isn't one of them......

Cheers

HERE WE GO !

Sorry but thats the nice explanation for a naive mechanic from the manufacturer.
It's like the politicians they have to sell us something with some positive arguments,
especially when we do not have the knowledge or means to proof them wrong.
EGR Theory:
EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx).
Under normal combustion, Nitrogen(N2)Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel
combind into water(H2O) Carbon dioxide (CO2) and the Nitrogen remains unchanged. Under very
hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms
Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and
becomes Nitrogen dioxide (NO2). In the presence of sunlight, it combines with other compounds
like Hydrocarbons and forms Smog. Since exhaust gas is inert (very stable) it doesn't burn again.
So by being introduced into the combustion chamber, it will lower combustion chamber temps
enough so that the Nitrogen doesn't react with the other compounds and is passed unchanged out
the tailpipe thus not contributing to smog. Now, since exhaust gas doesn't burn, it doesn't exactly
help with combustion. At higher RPM's, this really isn't noticable, but at idle, the reintroduction of
exhaust gas will cause a very rough idle and can cause stalling if to much is introduced into the
combustion chamber.
No I looked further into it because the engine I am getting has EGR difficulties reported all the
time .. service intervals are sometimes as low as 10k for the EGR valve. Since I pretty much
have to service my engine myself and with a friend (an auto mechanic) and have no warranty
(it's an import) I was looking closely what might cause problems. I have the diagnostic tools incl.
code readers and programmer so the electronics is not the issue but I don't want to order parts
for service all the time which are swapped under warranty .. I get them swapped but have to send
them back .. so whats the point on using something which is quite useless .. a diesel/LPG conversion
might do the trick for me to reduce the smoke to a level that I do not get in trouble with EPA
even if I loose my kitty ...
Well thats my take ... and I stick to it for my own reasons. If your mechanic things differently .. fine ..
Modern diagnostics in cars detect modifications .. so blocking an EGR with a state of the art car
will create an engine alert signal .. not sure about the Japanese ... so in order to avoid that there
are a few tricks you need to know on each car... but thats no secret ..
ok .. so that my last take on that subject ...
good luck
gmd

The EGR on my 79series filled the intake full of carbon and blocks up the cat converter - took a lot of effort to clean all the garbage out. Blocking off sounds like a good idea!!!

http://www.lcool.org/technical/70_series/egr_vent/vent.htm

It's geting harder to figure out who to believe, no maybe that's not the right way of putting it? WHAT THE HELL ???

I'm not saying you guys don't know what you're talking about but this machanic I have been talking to aint no dummy!

After reading the above post about the troopy, I'm stuffed!

The 3.0 Diesel mentioned here is Direct Injection I assume.

So the fuel goes directly into the cylinder.

The EGR goes into the airstream, so any heating the EGR does will be on the air (which will eventually heat the fuel).

But what would be the point of having an Intercooler to keep the intake air as cool as possible AND having an EGR to add heat ???

I would have conclude that EGR works only by changing the chemistry of intake air rather than the temperature.

Ok if running the EGR keeps the combustion cooler why do Nissan 3.0L engines burn piston 3 and 4 ?? The same pistons that the EGR feeds into.
Why do guys that have an EGT gauge report that after disabling the EGR valve they have lower exhaust temperatures ??
I fail to see how pumping extremely hot exhaust gas back into an already hot combustion chamber will lower exhaust temperatures.
Even with the lack of bang from lack of cool clean air coming into it in cylinders 3 and 4.
Why wasn't it done to cylinders 1 and 2 as well if it made that much difference.
In my opinion the EGR is only there for the engine to pass the relevant emission laws.

nonon

I think you may have misinterpreted what this mechanic told you, pre-heated fuel will have some minor benefits to combustion efficiency, but nothing worth worrying about. Putting hot exhaust gasses back in to the cylinder via the EGR will not heat the fuel, as it ignites virtually instantaneiously when it is injected in to the cylinder. Cold air is denser allowing you to pack more oxygen molecules in to a set volume like a cylinder, but in a diesel engine these get compressed so that they reach around 600 Celsius, so that the diesel will ignite when coming in to contact with the compressed and heated air. I think there are a number of people on this forum who will be trialing it, it will be interesting over the next couple of months when people start reporting on results.

Kind Regards

Snowy

Hello

The Gregory's Worksop Manual for the Nissan ZD30 TD says

"The EGR valve allows a precise amount of exhaust gas from the exhaust manifold to recirculate in the inlet manifold, thus reducing the temperature of the combustion process, which in turn reduces nitrogen oxide emissions. The amount of gas recirculated depends on the temperature of the coolant in the engine. When the engine is cold, idling or during full throttle operation no exhaust gas recirculation takes place."

The workshop manual and the Nissan Owners handbook do not mention routine maintenance of the EGR.

The workshop manual describes a method of testing for the correct operation of the EGR. They say to replace the valve if it is faulty.

I would not block or disconnect the EGR as it obviously reduces pollution.

Surely all 4wd owners and drivers are leaders in reducing pollution. We lead others follow.

Regards
Phil