Technical EGR Valve Operation

[s130]

Well, I've just replaced my EGR valve and cleaned the old one up.

For cleaning I used diesel fuel but I suspect that parafin and possibly brake cleaner will be OK.

Now for the puzzling operation details/questions.

When I split the old valve, solenoid from valve body both the valve body valves could easily be moved/depressed and returned OK to the sprung closed position.

The solenoid plunger, standing about 5mm proud of the housing, with a spring tension a little less than that required to move the sprung valve rod, could easily be depresssed into the solenoid housing. Using some grips and protective rubber I could NOT extract the solenoid plunger any further than it's 5mm rest proud position.

Connecting the old solenoid on its own and running the engine, or using FiatECUScan to activate the solenoid the plunger did NOT extend, however I could not easily depress the plunger.

So this makes me think that the solenoid is used to lock the valves in a closed position and that the EGR flow is based on positive exhaust pressure forcing the valves open unless they are positively held closed.

Any comments out there?

 

[s130]

Any comments out there?

YES I AM a silly boy.

Worked it out whilst going to sleep and just checked.

Valve is positively opened by the solenoid plunger. What fooled me is that the plunger is sprung loaded so when the solenoid is removed from the valve casing the plunger is fully extened. When assembled the plunger is actually pushed back into the solenoid till powered and then the plunger is forced forward to open the valve.

FYI the coil resistance is about 8.3 ohms.

 

[PaulD78]

FYI the coil resistance is about 8.3 ohms.

I take it this value is from the new solenoid

 

[s130]

Yes from the new, but I suspect the old was the same as it appeared to work ok.

The old one when testing took about 1.5Amps and 12/1.5 = 8.

 

[s130]

EGR Valve change update.

When I replaced the valve I put in the restrictor plate P/N:71751468

After doing this I noticed a small change in lift-off noise when the turbo is gently running. From new some 30K miles ago there was no noise. Post 30K miles there was a sound, rather like a panel or supspension creek at certain rpm & loads. So I eventually ignored this noise. I attributed it to turbo waste gate noise.

After fitting the restrictor plate the noise went from creek (100%) to creek (50% or less). In effect the noise double pulsed. Noted but not worried about.

A while later I found another noise change.

In the Croma when gently pulling a 2K rpm you normally hear the turbo as a gently shhh sound. Then I strated to hear shhhh....shhh...shh a gently subsiding quiver in the noise.

Suspecting a possible EGR gasket/plate leak I remove the EGR valve and plate. One could easily see very fine trace lines of soot across the faces.

So a possible leak. I replaced the units with Hylomar Blue not setting sealant and twas better but not perfect.

I now have on order two new soft metal crushable gaskets (I already have two in stock) and the later restrictor plate/gasket P/N:55225287

When these arrive I'll make a decision on the next step(s).

Go back to no restrictor plate or try the new restrictor plate.

What is bothering me about all of this is as follows.

1) restrictor reduces soot/crap being pushed back into the inlet manifold that over time could cause the swirl valves to gum up/sieze

2) restictor plate appears to benefit power/torque as by its introduction the fuel/air ratio is improved (note EGR flow is NOT metered)

3) exhaust gasses under pressure enter the EGR valve. When closed no pressure is exerted on the post valve and solenoid/inlet chamber. However when the valve is open the restictor plate will/could possibly increase the EGR chamber pressure which could add additional gas loading on the actuator valve seals.

So now I'm as confused as ever. I got to 41.5K miles on my original EGR valve/setup but did notice some lethargic moments in later life. No EGR valve failure as such.

Now I'm restarting the cycle and there appear to be other interesting factors appearing.

I'll keep you all posted as to what, how, why etc. I end up doing/experiencing.

 

[Radlet6]

The later one comes with a rubber sealing bead molded onto the face. I fitted mine as is with no bother.

 

[s130]

The later one comes with a rubber sealing bead molded onto the face. I fitted mine as is with no bother.

Interesting. Hopefully the bit will be at the dealer tomorrow.

Assuming a perfect gas seal we are now left with some questions / decisions.

Clearly the early EGR valves had issues, hence the four/five part number/design changes. During this 'change' period the restrictor plate was also introduced to (assumption here) reduce soot contamination without completely shutting off the EGR path and thus causing an EGR error. (note older ECUs, like the Stilo JTD, could have EGR completely blanked with no issues or ECU errors).

With no restrictor/(swirl) plate when the valve is open there will be less gass pressure in the exposed solenoid post valve chamber that can cause soot etc. to be pushed up into the solenoid internals. With a restrictor plate on the solenoid chamber outlet then there could ?????? be increased chamber pressure that could lead to addition solenoid seal loading.

HOWEVER, with the turbo running then the whole inlet manifold is pressurised so when the EGR valve is closed the solenoid chamber is under increased pressure anyway. I would expect the EGR to be closed when the turbo cuts in at around 2K rpm otherwise any boost pressure will be lost back into the EGR/exhaust stream. This overlap could possible account for the little kick that many see around 2K rpm.

My head hurts!!!!!!!!!

 

[Doofer]

Am I right in thinking that the EGR valve takes exhaust gases from before the particulate filter? If so that's idiotic - why didn't they run a pipe from the clean end of the filter? It's no wonder it and the inlet system get gooed up.

Or does it need the back-pressure caused by the filter to squirt the air in? Or possibly nobody thought about the sooty issues that would result.

 

[s130]

The EGR feed is taken directly off the exhuast manifold/turbo inlet pipe. Yes full of crap and pre turbo.

I posted a long while ago about my design modification to blank off the exhaust EGR feed and connect a small cone filtered cool air feed into the base of the EGR valve. The other solution is an additional feed pipe from the top/side of the air filter. This I belive was before I knew about the restrictor plate.

Whole design idea of feeding soot into an inlet manifold seems totally stupid to me. Before you know it we'll be needing chimney sweeps to clear our inlet manifold for us.

 

[s130]

Update:

This weekend I took the EGR valve off, removed the restrictor plate and removed all the Hylomar.

I then reffited with the later restrictor plate P/N:55225287 which has an integral rubber/silicone sealing strips on both sides.

The lift off noises and the shhhh quiver sound still exist.

I'm now concluding that the quivering shhhh is actually some form of feedback/noise effect from the restrictor plate. I'm quessing that there are some swirl effects going on.

As the Croma now pulls like a train with no hesitation or flat spots I'm going to accept the percieved? changes. MPG looks good as well.

I do of course have to option to return to the old gasket as I now have four "in stock"

I think I have more parts than many a Fiat dealers (big smiley).

It is amazing how over the years one builds up a stock of some items. I have a total of 35 valve shims to play with (8 in the 130TC) and 27 sitting in a multi-divide box coated in oil all set and ready for the 130TC's next major service. Last time a bought a shim some 7+ years ago I think they were £5+ each.

 

[s130]

The EGR feed is taken directly off the exhuast manifold/turbo inlet pipe. Yes full of crap and pre turbo.

I posted a long while ago about my design modification to blank off the exhaust EGR feed and connect a small cone filtered cool air feed into the base of the EGR valve. The other solution is an additional feed pipe from the top/side of the air filter. This I belive was before I knew about the restrictor plate.

Whole design idea of feeding soot into an inlet manifold seems totally stupid to me. Before you know it we'll be needing chimney sweeps to clear our inlet manifold for us.

NOTE! The clean air mod is NOT suitable for a Turbo Diesel so please don't try it.