Some thoughts on the 2.2 C5 EGR SYSTEM (Long)

cachaciero · Post by **cachaciero** » 28 Feb 2011, 10:06

Hi Mike

Go have a look at this for specific heats and gas constants
http://www.engineeringtoolbox.com/spesi ... d_159.html

Rgds cachaciero

Post by **Paul-R** » 28 Feb 2011, 11:00

That link doesn't work because of the full stop at the end of the sentence. It's a bugger being a (fellow) punctuation and grammar obsessive!

http://www.engineeringtoolbox.com/spesi ... d_159.html

Mind you, I could feel my eyes glazing over as I tried to digest a fraction of the information...

cachaciero · Post by **cachaciero** » 28 Feb 2011, 11:11

Dear me! that was quick

someone else with nothing else to do but wait for a new post

Thanks Paul I have corrected the link.

cachaciero

Post by **Paul-R** » 28 Feb 2011, 11:12

cachaciero wrote: someone else with nothing else to do but wait for a new post

Nah. It's just luck that I chose that moment to visit the forum.

Honestly...

MikeT · Post by **MikeT** » 28 Feb 2011, 19:58

cachaciero wrote:Hi Mike

Go have a look at this for specific heats and gas constants
http://www.engineeringtoolbox.com/spesi ... d_159.html

Sorry, I can't get my head round the chemistry and maths involved but if I were take a wild guess and given the CP's from that table, I think you're maybe trying to help me understand that displacing air (of which 78% is nitrogen) with some CO2 can not be the reason for the combustion heat reduction. Am I close?

According to wiki, it's yet to be discovered when, in the combustion process NOx actually forms. Seems there's three strong theories to chose from

Other sources tell me the magic temperature is around 2800F and that the amount of NOx formed is proportional to the excess oxygen available, though the info presented was limited to petrol combustion and very narrow AFR's.

All interesting stuff but still so much to learn....

Having said all that, I realise I'm taking this thread somewhat off-topic, for which I apologise.

tonto · Post by **tonto** » 28 Feb 2011, 20:26

My 1st post so go easy please Hi cachaciero
Is your car running any better since you put the EGR3 in.
I am having problems with acceleration,going up thru the gears the car is very slow to pick up speed until the turbo kicks in at about 2,300 revs..
I am hoping my egr is gummed up and that EGR3 will maybe solve the problem,which brings me to..where exactly do put I the EGR3 in,(is it before the MAF or immediately after the MAF

) Sorry I'm not very tech minded.
Thanks for this great and enlightening thread. TIA
Dave
nearly forgot c5 2001 2.2 hdi sx 110K miles

cachaciero · Post by **cachaciero** » 28 Feb 2011, 21:01

Mike

I don't see that you are talking the thread of topic it's all EGR relevant.
I keep hoping that someone who is a real Fluid Dynamics Guru will come on and give us all a master class in the combustion process

To comment on the rest of what you have said IMHO

1. The heat of combustion will be proportional to how hot the gas mix was immediately prior to combustion plus the quantity of fuel times it's calorific value. This assumes that there is sufficient oxygen to allow complete combustion of all the available fuel.
2. At some small time after combustion the temperature will be proportional to the sum of 1 minus the heat absorbed by the engine casings minus the heat absorbed by the inducted gas charge minus heat taken by any other exothermic reactions ( NOX production).
3. As some further time after detonation this gas will now be expanding and pressure will start to fall therefor it's temperature must also start to fall.

So all I am saying is that in a perfect world combustion temperature has little to do with other gases. However in the real world we know that fuel air mixing is imperfect and that if the absolute correct quantity of oxygen was admitedled for the quantity of fuel then not all fuel will get burnt, which is why an excess of oxygen is required to ensure more complete combustion.
What comes out of the exhaust however will depend on the gases inducted both in mass and how much heat they can absorb in time, this does seem to be quite a complicated area and both the gas constant and specific heat seem to be quite different for Nitrogen and Co2, this will make a differnce to the pre-combustion temperature as well as the post combustion temperature.
Inconclusion at a simplistic level it is my belief / understanding that EGR ensures a cooler burn by reducing the amount of oxygen available for the burn, this will result in a cooler burn and a less complete burn with more soot production.

Production of NOX the only thing I know about it is that there has to be a surplus of oxygen molecules to combine with Nitrogen 2800 doesn't sound out of the question, however if nobody realy understands what happens then basically all the EGR systems must be being designed with a "finger in the wind" which may explain why some don't seem to do so well

cachaciero

MikeT · Post by **MikeT** » 01 Mar 2011, 16:02

cachaciero wrote:Mike

I don't see that you are talking the thread of topic it's all EGR relevant.
I keep hoping that someone who is a real Fluid Dynamics Guru will come on and give us all a master class in the combustion process

Indeed! I suspect he/she is in great demand though and too busy.

Now to muddy (or perhaps clarify) the waters further, I found this summary...

"Using computational analysis, it is shown that lower exhaust soot emissions for the lower EGR dilution cases (45 per cent) are due to higher soot oxidation rates, and lower exhaust soot emissions for very high EGR rates (70 per cent) are due to lower soot formation rates. The trend seen in NOx emissions are primarily attributable to the inert effect of EGR dilution and varied ignition delay caused by varied percentages of oxygen in the intake mixture."

cachaciero · Post by **cachaciero** » 01 Mar 2011, 20:33

[quote="MikeT] "Using computational analysis, it is shown that lower exhaust soot emissions for the lower EGR dilution cases (45 per cent) are due to higher soot oxidation rates, and lower exhaust soot emissions for very high EGR rates (70 per cent) are due to lower soot formation rates. The trend seen in NOx emissions are primarily attributable to the inert effect of EGR dilution and varied ignition delay caused by varied percentages of oxygen in the intake mixture."[/quote]

Gulp!!!!! did you understand that.......???

cachaciero

cachaciero · Post by **cachaciero** » 01 Mar 2011, 21:05

tonto wrote:My 1st post so go easy please Hi cachaciero
Is your car running any better since you put the EGR3 in.
I am having problems with acceleration,going up thru the gears the car is very slow to pick up speed until the turbo kicks in at about 2,300 revs..
I am hoping my egr is gummed up and that EGR3 will maybe solve the problem,which brings me to..where exactly do put I the EGR3 in,(is it before the MAF or immediately after the MAF ) Sorry I'm not very tech minded.
Thanks for this great and enlightening thread. TIA
Dave
nearly forgot c5 2001 2.2 hdi sx 110K miles

Hi Tonto

Welcome to the mad house

If you are not very tech minded now then you will need to start getting tech minded to understand the car you have

If that's what you want to do fine you will find a lot of help here but if you don't then maybe a C5 is not for you as it is a complicated car and lots of garages don't really understand them either.

O.K first thing that you need to look at is swirl valve operation, 2,300 rpm is a very significant number on the 2.2 because that is the point when the swirl vave should open, effectively the second inlet valve.
Now if the system is not working properly then the swirl valve will likely be open as the default, failed electro valve, or no vacuum is open. If this is open the characteristics will be exactly as you describe, The second valve needs to be closed at low revs otherwise the engine is gutless.

You need to locate the swirl valve operating arm and check that with the engine stopped it is forward and once the engine is started at idle it should be to the rear. If this doesn't happen then as a simple test take the operating arm of the cank and tie the crank to the rearward shut position using a bit of string wire or cable tie, then go drive the car you will find a lot of difference

.
Now I could write a lot more about this but it has been done to death on this forum, just do a search using my name and swirl valves and you will get chapter and verse on how to diagnose problems with this system, any specific questions just come back and ask.

Now as regards EGR3 well you have two ways of going ,
1: disconnect the big fat air pipe that goes into the manifold and inject directly into the manifold with the engine running at about 1.5 2K rpm, suitable size stick holding the pedal, doing it this way will allow you to feel air coming out of the rubber pipe this is from the turbo and should be a reasonable flow, proves your turbo is working

2: Now when I did mine I couldn't see any reason why I could not remove the air cleaner top rotate it 90 degrees and inject there, this way the MAF get cleaned as well as any crud in the air side of the turbo so that is what I did seems to have worked.
My impression was that after one can the tickover was a bit smoother as was pickup at low revs as for improvment in fuel consumption well jurys still out on that but if there was any it is small at least on my normal journeys.

cachaciero

KevMayer · Post by **KevMayer** » 01 Mar 2011, 21:11

Have you noticed any change since using the EGR3?

There seems to be a noticable improvement in the way my C5 is running. Although, at 141K miles, I've actually squirted in 3 whole cans of EGR3 up to now (on 3 seperate occassions).

I've got one more can to squirt in, just for good measure.

I think it must have cleaned out the EGR system because while I applied the third can today I actually got some of it blowing back out of the inlet pipework. This back pressure can have only come from the EGR and, this would explain why you sometimes see oily deposits in your air ducting on the air filter side of the crankcase breather connection.

MikeT · Post by **MikeT** » 02 Mar 2011, 11:51

cachaciero wrote:
MikeT wrote: Using computational analysis, it is shown that lower exhaust soot emissions for the lower EGR dilution cases (45 per cent) are due to higher soot oxidation rates, and lower exhaust soot emissions for very high EGR rates (70 per cent) are due to lower soot formation rates. The trend seen in NOx emissions are primarily attributable to the inert effect of EGR dilution and varied ignition delay caused by varied percentages of oxygen in the intake mixture."
Gulp!!!!! did you understand that.......???

Sort of, but I had the benefit of reading the chapter it summarises so it made sense around the tenth reading for me.

It explained how EGR dilution retards ignition and flame propogation (lowering air charge and combustion temperatures), affects the amount of pollutants created on ignition and how much is consumed in the burn.

At least, the effects of oxygen content on combustion temperature is now clearer to me.

tonto · Post by **tonto** » 03 Mar 2011, 19:45

Hi cachaciero

I checked out your old post re swirl valves,very interesting.
Well..Had a look at the way the swirl valve behaves at no start and started.
The wee metal rod is attached to both ball joints and is moving as you say,so am I taking it for granted that it is working ok.?
I bought a can of EGR3 today and squirted it in as you suggested,and the engine management light came on along with antipollution fault on the screen. Anyway took it for a spin,did not notice any difference in acceleration maybe due to the fact the engine management light was on.
I tried disconnecting the battery and doing a reset,but the light just stayed on....One good result tho,I went out to the car about an hour ago and.....The engine management went out ,took it for another spin and did not notice any real difference.Do you think another can of EGR3 would help.Any suggestions would be welcome TIA
Dave

cachaciero · Post by **cachaciero** » 03 Mar 2011, 21:16

tonto

Re swirl valves, the problem with the system is that it is a vacuum capsule pulling against a spring a partial loss of vacuum and the arm may move but not fully, I would suggest that with the engine running you apply a bit of finger pressure to the ball joint just to check that the valves are indeed fully closed.

As regards the EGR3 cleaner I really don't know, the use of EGR3 is a new subject on here and is effectively an experiment by myself, kevmayer and now you. I think that both kev and myself feel that for a car with about 100K on the clock that has never been treated then at least two cans will be required to stand any chance of removing all the crud which can build up in the inlet side due to EGR operation.

However at least in my case I am looking for an improvement in fuel consumption rather than performance per se and if I could see an improvement of 1-2 mpg I would consider the experiment worthwhile.

In your case I am not convinced that your lack of low down performance is due to a coking of the inlet tract simply because you appear to have significantly poor performance low down.

Your experience of getting the anti-pollution light on after use mirrors my own, out of interest where did you inject the fluid ? Let me guess from the top of the air cleaner?

cachaciero

tonto · Post by **tonto** » 03 Mar 2011, 22:28

Hi cachaciero

Thanks for the reply,Yes I loosened the 4 screws on top of the air filter,loosened the jubilee clip behind the MAF and turned the top of the air box sideways and injected the EGR3 directly into the MAF.(hope that was the correct thing to do) Tomorrow I will check that the rod with the balljoints is moving as it should, Should I notice a change in engine speed or anything when I apply a little pressure to the balljoint.
I had to go out again tonight and I must say I felt the engine was pulling slightly better than it has been,the engine seems to run out of revs tho at about 3500 to 4k,Tomorrow after I have injected another can of EGR3 I will take it up the city bypass and try and give a bit of welly (if I can get a clear run) and hope it might clear itself a bit better.I will post again with better news I hope...Thanks..PS. is it possible the s/valve diaphram is holed.
Dave