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Discussion Starter · #3 ·
FV-QR

Quote, originally posted by Hendrik »
AFAIK, the RS4 valve has a limit of 136 bar...

The RS4 fuel return valve replaces the OEM one. The OEM one opens a return valve at 130bar and allows pressure to drop to as low as 127bar before building pressure back up again. On the RS4 valve the pressure is designed to go to 136 bar and then the return valve opens, but closes again at 130bar. All depending on requested rail pressure.
REVO Stage 2+ requests 130bar and then higher in the rev range 132.5bar around the mythical 5krpm mark.
Before I had the valve, my actual rail pressure never managed to meet requested pressure apart from the point where I let off WOT. This POSSIBLY could point to a performance dip if the ECU detects the inability to meet requested pressure and then back off the power.
 

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Re: (staulkor)

Quote, originally posted by staulkor »
How difficult is it to get to the valve? I was thinking about upgrading as I am a few bar lower than requested in upper RPM.

ECS and world impex or whatever it's called carries it. It's 100 bucks shipped.
I'm running one. I get well over the Revo requested fuel pressure amount. My LPFP duty % valve went down drastically.
 

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Re: FV-QR (LEWXCORE)

Putting this on will give an extra 73ish psi. My math isn't the greatest off the top of my head. Lol.
Running a 630cc injector at 3 bar is completely different at 4bar.
I'll be getting on the dyno shortly to see if it has effected my power curve. The car feels much more responsive with it.
 

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Re: FV-QR (LEWXCORE)

Quote, originally posted by LEWXCORE »
so our fuel rail is for 130bar, the rs4 is for 136bar, doesn't seem like it should make a huge difference... other options anyone? arin?

most folks average 120-127bar on the stock valve. Even if the request is 129.99.
With the rs4 valve Im well over the requsted amount
 

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Re: FV-QR (LEWXCORE)

Quote, originally posted by LEWXCORE »
so our fuel rail is for 130bar, the rs4 is for 136bar, doesn't seem like it should make a huge difference... other options anyone? arin?

It depends how far you are pushing everything but I think you may find you'll run out of high pressure fueling, essentially maxing out the hpfp. Adding the 136 may not really help as you may not even be able to achieve above 130 depending on how much fuel you are using.
 

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Re: FV-QR ([email protected])

i'd like to see more info on this especially from people who are actually running the valve. Any downsides to running the valve? Increased stress on HPFP? Are there noticeable gains to be had if you aren't currently experiencing problems? Are people with problems masking their real problem with this? This seems to be a mod that hasn't really been talked about much when it appears to have a plausible worthwhile advantage.
 

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Discussion Starter · #17 ·
FV-QR

There is also a by-product of fitting the RS4 valve and this is that it alters the pressure in the in-tank low pressure pump. The OEM low pressure fuel pump before the valve was fitted started off at 4.5bar pressure, but gradually dropped to around 3.4bar pressure at higher revs when WOT. After the RS4 valve was fitted the in-tank pressure stabilised at between 4.1-3.9 bar across the entire run whilst WOT. This too could point to where you would get a drop in power around 5krpm as the in-tank low pressure fuel pump drops below 3.5bar around those revs, which is outside normal parameters and MAY cause fuel cuts or the ECU to back off the power.
The RS4 valve can cope with up to 150bar of pressure requests (GIAC Extreme Beta file testing), which is the limit of the high pressure fuel pumps anyway.
I must stress that all this is from readings taken from live logging on my car, but the diagnosis is subjective although compelling in the logic.
The valve costs under £50, but is a pig to fit as it is located under the intake manifold and at an awkward angle to reach with spanners. I for one think it was worth it, just for peace of mind that it eliminated another variable from the "power dip syndrome"
 

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Re: FV-QR (CupraK1)

Were you able to change the valve out without removing the intake manifold? I might have to run some logs to see what kind of values i'm getting right now and then just try this valve to see what happens afterwards. I'm not really convinced yet that i NEED it or would benefit from it though.
 

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Re: FV-QR (ndifadvokit)

Quote, originally posted by ndifadvokit »
Were you able to change the valve out without removing the intake manifold? I might have to run some logs to see what kind of values i'm getting right now and then just try this valve to see what happens afterwards. I'm not really convinced yet that i NEED it or would benefit from it though.

Pretty damn hard to remove it when the intake manifold is on the block. It's soooooo much easier with the manifold off.
 

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Re: FV-QR (CoNGLoMeRaTeGTi)

Quote, originally posted by CoNGLoMeRaTeGTi »

Pretty damn hard to remove it when the intake manifold is on the block. It's soooooo much easier with the manifold off.

When you say it's hard to do it do you mean it's in a tough place but if you can manage to reach it it comes out easy or do you mean it will take me longer to change it that way than remove the whole manifold? I personally thought it was pretty easy to remove my intake manifold but it wasn't a 30 min job. How are you liking your rs4 valve? Would you recommend it?
 
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