Fuel Rail Pressure Limiting Valve

[camoto]

I am just wondering if anyone has had to replace one of these?

Ever since going to APR Stage II+ (and still with Stg 3) I get a slight surging in higher RPM's in higher gears. I pulled logs today and noticed during the surge my fuel rail actual pressure held steady until about 5000 RPM then it spiked to 127, fell down to 115@5600 RPM then spiked up again to 128@6000 then crashed to 109@6320 and back up 126@6600.

Something about this screams pressure limiting valve to me, but it's just a hunch.


The other odd thing is that I was under the impression that the APR S3K04 93 Octane file was supposed to specify 130 bar, not 120 (can anyone confirm this?)

[Operator]

I went with this when I installed the K0R: http://hpfpupgrade.com/Products/Show...nce+Rail+Valve

Not sure if you've read through this yet:
http://www.audizine.com/forum/showth...l-Issues/page3

[NorcalPB]

I did some research on this last night too. I think even if you have the upgraded valve from the later b7's, at stage 2+ it's probably best to get the RS4 valve or one of the aftermarket ones to ensure that flow is not limited. Plus you can be all like, "I have RS4 components in my engine, it is for teh moar power". And I know everyone here wants to say that lol.

[camoto]

I went wit this when I installed the K0R: http://hpfpupgrade.com/Products/Show...nce+Rail+Valve

Not sure if you've read through this yet:
http://www.audizine.com/forum/showth...l-Issues/page3

Wow. No I didn't see that thread until now. APR has my logs and it will be interesting to see what they say. I think I'll be upgrading this either way. The only thing that makes me wonder is that I have a 2007.

What about requested pressure? Does 120bar seem correct?

Thanks!!!!

[bman005]

The upgraded valve is a good idea for sure! I'll be doing that come spring time.

[Mc Suly]

I got 145BAR from HPFP Upgrade .com

Going in 2 weeks.
I'm low on $$ since i had to pay $400 to renew my papers & license llol

[shiro1745]

Wow. No I didn't see that thread until now. APR has my logs and it will be interesting to see what they say. I think I'll be upgrading this either way. The only thing that makes me wonder is that I have a 2007.

What about requested pressure? Does 120bar seem correct?

Thanks!!!!

definitely let us know what APR has to say about this. and just to keep things in one place maybe you should just post in the other thread pointed above. just saying ..

[Operator]

Wow. No I didn't see that thread until now. APR has my logs and it will be interesting to see what they say. I think I'll be upgrading this either way. The only thing that makes me wonder is that I have a 2007.

What about requested pressure? Does 120bar seem correct?

Thanks!!!!

I don't have the specs right now, but 120bar does seem a bit low for the K04. Even at Stage II+ I thought the request was higher than that. Even Audi changed from the 116bar valve for OEM......

[camoto]

I already ordered the Valve from HPFPupgrade. I plan on changing it out no matter what but I want to see what APR says first. I'll post a full follow up in the other thread if/when I know more.

[jimrobbington]

Pretty sure most stage 2+ files request 130 bar. Your valve is dumping at 126, then rebuilding, then dumping. It forces hot fuel back through the hpfp. You will not feel fuel cuts this way, but you hit a fueling wall. Definately swap that out asap and you should have no more problems!

JR

[plokm]

you will need a long extension and a crow foot

[camoto]

you will need a long extension and a crow foot

A 17mm and a 14mm, right? Do you have torque values?

[CorneliusRox]

you will need a long extension and a crow foot

just to get the return fuel line off? it looks like everything could be done with open ended wrenches (just curious).

Also, has anyone just plugged this instead of running a valve? If the system goes by what is requested, I dont think it would be an issue?

[golfvdude]

just to get the return fuel line off? it looks like everything could be done with open ended wrenches (just curious).

Also, has anyone just plugged this instead of running a valve? If the system goes by what is requested, I dont think it would be an issue?

It is located under your intake manifold. A regular wrench will be difficult to use. Locate your valve and you'll see why the crow feet will work better.

[plokm]

you will need to remove a few screws to allow you to shift the fuel rail around so you can access the valve better

[CorneliusRox]

dang, I was looking for it. do you have to take off the throttle body to get to it?
seems like taking off the intake mani would be easier than trying to fish around it

[golfvdude]

dang, I was looking for it. do you have to take off the throttle body to get to it?
seems like taking off the intake mani would be easier than trying to fish around it

http://www.audizine.com/forum/showth...l-Issues/page5

Post #173. I put a basic outline on what needs to be done. It really is a simple task once you locate all the components. Didn't take me long to do. Probably 30-45 mins the first time you do it.

[plokm]

dang, I was looking for it. do you have to take off the throttle body to get to it?
seems like taking off the intake mani would be easier than trying to fish around it

removing the intake mani might take longer because you have to remove alot of screws that is hard to find and get too

[CorneliusRox]

well thanks for the info. I suppose, taking the TB and intercooler hoses off will free up a ton of space.

Has anyone tried just plugging the valve instead of replacing it? I have done it on CR diesel's with no issues since the ECU requests how much it wants.

[jimrobbington]

Has anyone tried just plugging the valve instead of replacing it? I have done it on CR diesel's with no issues since the ECU requests how much it wants.

That seems like it would work, but, I mean, they had to have known what they were doing putting that in there.

JR

[DRAKLORE]

I'd imagine if
You plugged it, it would
Work fantastically! Untill your fuel system fails and there's noplace to safely bleed that extra 10000 psi...

[CorneliusRox]

I'd imagine if
You plugged it, it would
Work fantastically! Untill your fuel system fails and there's noplace to safely bleed that extra 10000 psi...

agreed. I think it is and should be a last resort bleed off so you dont have rail flying all over when it bursts. The guy I helped with it didnt want to shell out the $250 for the higher pressure valve. So far no issues, and he is at 36000psi I believe. Yeah, no spelling error. CP3's are one hell of an injection pump (HPFP) system.

[b7kevin]

Anyone have a chance to swap the valve out with pictures

[camoto]

FYI - Still no report from APR on my original issue. I have the valve on order (it's being shipped now). If I get the valve before I hear back from APR I might just say screw it and install it before hearing their assessment on my logs.

I'm slightly disappointed (but not surprised) that it takes so long to hear back. Not even a "hey we have your logs but we are busy, we'll get back to you by XXX".

[camoto]

OK so I just called, asked for customer support and asked all of the questions I had about what is going on with this other than waiting for an analysis and got some acceptable answers.

1.) the fluctuations I am seeing are "on the high side" of unacceptable and my problem "could" be the PRV.
My take: I will change the PRV
2.) my specified pressure of 120 bar is not abnormal. It all comes down to what the vehicle is requesting. It could have been a number of factors.
My take: This is probably why the surging is more apparent in cold dry air. The ECU probably requests 130 bar in cold dry air, exacerbating the PRV issue.

I will change the valve out (when it arrives) and pull logs again and post my results. Wish me luck.

[CorneliusRox]

good luck!

[camoto]

Update:
Got the valve in the mail today. I originally was going to pay to have it installed but after looking at it, I was convinced I could do it myself.

Here's what I did:
Pulled fuse 28
Idle car until dead
Using a narrow 14mm flare nut crow's foot, loosen fuel line coming out of the valve
remove the three screws on that same line, loosening the entire line so you can move it out of the way
loosen the valve with a 17mm narrow flare nut crow's foot
unscrew it by hand (this is a really tight fit)
using about one layer of electrical tape, tape the new valve to the end of an extension (so it's still floppy, like a universal fitting)
screw the new valve in like this, then using the crow's foot, tweak it a bit
now "unscrew" the tape from the valve
put the clamps back on and the line
torque everything
put fuse in, turn on ignition, leak test
start car, let idle, leak test
run car up under load, check for leaks

(that's right, I didn't remove the throttle body....)

with all of those steps it took about 90 minutes and was only mildly stressful. It's important that you take your time, have the right tools and maybe a friend to hold the light.

I wasn't able to get a full logging run in, but I did get some partial runs (traffic). The pressure does not appear to be swinging in extremes any more and appears to be holding a LOT better. Also, I didn't experience the excessive surging, but I will need to get a real 4th gear run in to redline to really know for sure.

overall a minor success I think. If the problem comes back, I'll post about it, but honestly, my gut tells me it's resolved.

thanks for all the help and thanks to hpfpupgrade.com for the valve!!!

[golfvdude]

Thats great to hear! Glad you did it and not pay someone as it is fairly easy to do. I took off the throttle body and it took a little less time but either way, there's no snag so to each their own! Please give us some logs when you get a chance. It would make me feel better about my investment....hehe

[camoto]

This was the best run I could get in without killing a family of 8 in their minivan. I just ran out of runway to get a decent run in but this was 4th, and it looks way different:

[p1nk50ck]

obviously right now, since you're testing, your fuel mileage will probably be crap, but can you please give us an update in a couple weeks or so, to let us know if you're getting significantly worse gas mileage or not after the fuel valve?

i assume it'll only flow what it's requesting, and it's really only "starving" at the upper RPMS, so i would assume that there shouldn't be a change.

[camoto]

Sure thing. Most of my driving is commuting in bumper to bumper traffic, so I am usually idling along, but I will post a couple of updates. I definitely would like to get the full 4th gear pull logs up for everyone to see. Honestly, I am a little disappointed that APR doesn't advise customers of the probability of this issue so I don't mind getting the word out.

[Ves]

^ this is good to know considering i am planning on going the apr route. very curious to see if the valve changes your low rpm gas mileage!

[CorneliusRox]

The valve change should not effect gas mileage at all. Your normal MPG isnt based on pinning it, and that is pretty much the only time the PRV will be used to it's potential. :-)

[CorneliusRox]

just thought I would throw this in here to show where the PRV is. Looks like the easiest way to get at it would be taking the mani off.

[camoto]

just thought I would throw this in here to show where the PRV is. Looks like the easiest way to get at it would be taking the mani off.

Depends on how you define "easy"! Personally, I didn't find it that difficult changing it out the way I did it, but if you have limited patience and aren't comfortable working in tight spaces, you are probably correct.

[CorneliusRox]

Depends on how you define "easy"! Personally, I didn't find it that difficult changing it out the way I did it, but if you have limited patience and aren't comfortable working in tight spaces, you are probably correct.

agreed. I just didnt see it when I looked (at night, for 1 minute lol) so I ran across this and thought I would post it for anyone else.

[DRAKLORE]

If your short on patience than I really don't suggest removing the intake manifold...

[viziers]

If your short on patience than I really don't suggest removing the intake manifold...

True that! Although I have modified most of the stuff around the intake manifold to make it easier to take it out..





vizi

[lIRATIl]

Any way to do this without the crows feet? And did you use any extensions on the crows feet?

[camoto]

Any way to do this without the crows feet? And did you use any extensions on the crows feet?

If you can do this (without taking the manifold off) without a good thin crow's foot and an extension, you should be a mechanic for a living. I don't see how you could ever get in there with anything else. Look at it on your car and put your hand in there and you'll see what I mean.