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Old April 1st, 2008, 13:12   #1
greenskeeper
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Default case relief valve psi

So I saw a few posts on the case relief valve recently. Decided to take a look at mine.

It was in pieces, or at least all the "guts" were out of the valve.

I reasembled everything and the car ran wierd. It was really noisy and the timing peaked at 30 degrees even at only 2500rpm. I think the max timing should be 18 degrees? I only drove like this for about 1/4 mile before diesel started puking out the front of the car!

The seal at the top of the IP blew out. Luckily I was able to take the cover off and reasemble with no leaks.

I punched the valve without the guts to bring the center piece back flush with the top of the valve.

So;

After I reasemble the valve, how do I set it to the correct pressure? How do I test the pressure? What is the pressure for the valve? Is there a measurement for how far the center of the valve should be depressed when looking from the top? That's the only thing I can figure unless I can somehow test the pressure? Maybe resort to getting a new valve?
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Old April 1st, 2008, 13:33   #2
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That relief valve isn't a fixed pressure. It, and the restriction in the return banjo bolt, act together to give a somewhat-linear pressure gradient wrt rpms.

No-one has ever been able to tell me what the pressures for an electronic pump are, but if memory serves the older M- pumps are something like 120psi at full revs.
As this pressure is leaked-off by the n109 to fine-tune the timing I'm not sure just how critical it is, even.
n109 duty cycle is worth looking at, tho...
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Old April 1st, 2008, 13:51   #3
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EDC controlled VE injection pumps should peak at 10 bar at redline. The pressure can vary with pump rpm and injected fuel quantity.

The pressure can be adjusted by moving the internal slider and increasing spring tension. This would be of some benefit on engines run at high rpms for extended periods where air bubbles can form and reduce the high stage efficiency in terms of filling the compression chamber.

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Old April 1st, 2008, 14:39   #4
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When I took the valve out, the center was depressed quite a bit. Maybe too much to cause the guts to come out?

Then when I reasembled the guts the pressure was way too high causing the seal to fail?

Currently the valve is intact but the center is almost flush with the edge - but I haven't blown a seal yet.

I am wondering what the ideal setting is for that valve and perhaps now I have it too low?

This is a new pump from vw that I have had on the car for about 40k miles without issue.
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Old April 1st, 2008, 14:51   #5
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It sounds like your return line is clogged if you are puking this valve. Your pump timing is critical to the case pressure that controls it. If you saw 30 degrees advance, with proper case pressure, you should get vagcom and retard/correct your timing.

Clean or replace your thermostatic tee on the fuel filter. Or get an old TD fuel filter and straight nipple to eliminate the tee.

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Old April 2nd, 2008, 01:16   #6
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Interesting, Jeff. So how close to the optimum advance curve would/could one get based purely on case pressure and timing piston spring/shim? Is it possible to massively exceed requested advance at all levels of speed/load?

Or conversely, is case pressure sufficient to offer *some* advance even if the n109 is being driven towards zero advance?
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Old April 2nd, 2008, 02:59   #7
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Quote:
Is it possible to massively exceed requested advance at all levels of speed/load?
This is what happened to me with the valve reassembled. 30 degrees advance at light load and only 2500rpms!

Now the timing appears normal (17 degrees at full load, full rpm) with the valve reasembled but with the center almost flush with the edge.

The return line is clear - no obstructions.

What I'm trying to determine is how that valve should be set...how much pressure is the correct amount without blowing seals or messing up the timing.
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Old April 2nd, 2008, 06:12   #8
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New ones are flush. That's wher I set ALLof them and I have yet to have a problem at that spot.
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Old April 2nd, 2008, 12:54   #9
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Thanks.

With mine flush, I am only getting 12 degrees of advance at the maximum.

So I took out the valve and punched it a tiny bit lower into the top of the body. Now I am getting 17 degrees advance at the max - sound about right?

The mechanical timing is at the top of the 3 line chart. adaptation is at 33000 as per jsrmonster which is about 2.5 degrees of advance at idle.

I'll assume the pump pressure does something to the timing ability of the pump?

Originally the center portion was well recessed from the top of the valve, but perhaps the guts were out so it didn't make a difference until I pulled the valve and unknowingly reasembled? Maybe a faulty valve (too far recessed) from the factory causing the guts to blow out the first time it was run?

Just thinking aloud at this point!

All seems well as far as I can tell with how I have it set now.
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Old June 18th, 2008, 01:36   #10
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Anybody have a measurement for the depth of the center part of the valve (outside the IP)? Would be a big help in setting mine correctly.
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98 JETTA TDI (SOLD) PP764s, RC3, 5deg advanced, 0.68 5th
97 F-250 Crew Cab 4x4 7.3L PSD E4OD (stock)
99 F-250 Crew Cab 4x4 7.3L PSD ZF-6 (4" turbo back, Hydra chip)
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Old July 7th, 2008, 11:31   #11
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I'm asking about the recessed center part depth where you put the 10mm wrench to remove - don't even have to remove from the car to get a quick measurement...
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