RS4 Fuel Pressure Regulator Return Valve (135 bar) for APR K04 Upgrade? - BPY Engine Code

[Ignignokt]

I dug up an old thread that had this part (079 130 757) listed as being recommended. Is that still the case? I'm getting my parts together and this is one that stuck out.

I'm currently APR Stage 2 and have all supporting K04 mods installed except the injectors and turbo (obviously).

 

[ROH ECHT]

Need to list the K04 tune you plan on going to. Most canned tunes require only the oem fprv 130 bar fprv. Even APR doesn't require you upgrade the fprv. The RS4 is a 135 bar fprv.

However, some custom tunes allow one to use a HPFP upgrade that can produce more rail pressure and thus would require a higher pressure limiting valve on the rail. Such as a company that makes stages of hpfp upgrades; https://www.vismotorsport.com/20tfsihpfpupgrade

I had a tune once that had a 142.5 bar rail target. That is when I installed a 145 bar fprv. APR's stage 3, or S5 4.2L FSI V8, fprv is a 155 bar and would work for tunes when more than 130 bar target is set as the rail pressure target.

APR says their hpfp upgrade produces a bit more than a 40% increase in rail pressure.
Autotech says 50%.
VIS says their stage 1 = 55% more piston area.

So, any of these will suit canned tunes for a K04 w/hpfp upgrade, and no fprv is needed for canned tunes. I am back to my original GIAC K04 H.O. tune (requires an upgraded fprv)...and target never exceeds 140 bar per the H.O. tune.

 

[Ignignokt]

Need to list the K04 tune you plan on going to. Most canned tunes require only the oem fprv 130 bar fprv. Even APR doesn't require you upgrade the fprv. The RS4 is a 135 bar fprv.

However, some custom tunes allow one to use a HPFP upgrade that can produce more rail pressure and thus would require a higher pressure limiting valve on the rail. Such as a company that makes stages of hpfp upgrades; https://www.vismotorsport.com/20tfsihpfpupgrade

I had a tune once that had a 142.5 bar rail target. That is when I installed a 145 bar fprv. APR's stage 3, or S5 4.2L FSI V8, fprv is a 155 bar and would work for tunes when more than 130 bar target is set as the rail pressure target.

APR says their hpfp upgrade produces a bit more than a 40% increase in rail pressure.
Autotech says 50%.
VIS says their stage 1 = 55% more piston area.

So, any of these will suit canned tunes for a K04 w/hpfp upgrade, and no fprv is needed for canned tunes. I am back to my original GIAC K04 H.O. tune (requires an upgraded fprv)...and target never exceeds 140 bar per the H.O. tune.

That's some good info. I'm going with APR's K04 tune. My IE-upgraded HPFP claims +50% output.

The part looked to be more of a "nice to have" instead of a must. So, I figured I'd ask around. Thanks!

 

[ROH ECHT]

IE hpfp is good, APR K04 tune should be a 130 bar max...matching the oem fprv. If you eventually see the rail pressure actual not able to reach the 130 bar target, it may be one of a few things; fprv failing, injector/s leaking, or the hpfp is failing to make pressure...and if it's not the fprv or injectors, then the hpfp itself may be failing, or the cam's tri-lobe may be worn at its peaks.

You haven't installed the hpfp yet at stage 2, and are you aware of the need to change the future CF(cam followers) much more often? When you first upgrade the hpfp, install a new cam follower. It should last 10k miles and then change it. You will be changing the CF often, so you may want to consider swapping the hpfp bolts over to the hpfp stud conversion kit; ( https://www.urotuning.com/products/fuel-pump-bolt-to-stud-kit-2-0t-fsi-hpfp?variant=8385058406455 ). Inspect the black DLC(diamond like coating) that contacts the tri-lobe to determine if the next cam follower change can be extended or not by assessing how much of the black coating is missing. I typically change the cam follower when any of the coating is worn away.

I believe I have vids for both the cam follower change and tips for the hpfp stud kit; https://www.youtube.com/user/zoomdis/videos

 

[Ignignokt]

IE hpfp is good, APR K04 tune should be a 130 bar max...matching the oem fprv. If you eventually see the rail pressure actual not able to reach the 130 bar target, it may be one of a few things; fprv failing, injector/s leaking, or the hpfp is failing to make pressure...and if it's not the fprv or injectors, then the hpfp itself may be failing, or the cam's tri-lobe may be worn at its peaks.

You haven't installed the hpfp yet at stage 2, and are you aware of the need to change the future CF(cam followers) much more often? When you first upgrade the hpfp, install a new cam follower. It should last 10k miles and then change it. You will be changing the CF often, so you may want to consider swapping the hpfp bolts over to the hpfp stud conversion kit; ( https://www.urotuning.com/products/fuel-pump-bolt-to-stud-kit-2-0t-fsi-hpfp?variant=8385058406455 ). Inspect the black DLC(diamond like coating) that contacts the tri-lobe to determine if the next cam follower change can be extended or not by assessing how much of the black coating is missing. I typically change the cam follower when any of the coating is worn away.

I believe I have vids for both the cam follower change and tips for the hpfp stud kit; https://www.youtube.com/user/zoomdis/videos

Thanks again for the fueling info. It's one thing I've never really given much thought to until now.

I've had the pump installed for a couple years and been Stage 2 for 5 or 6. I had the stud conversion and ditched it bc it made CF inspections & changes a gigantic PITA. Not a fan at all. That won't matter for much longer anyway bc I have the TSI roller conversion waiting on me to install. Will probably do the cam chain and tensioner while I'm in there.

 

[ROH ECHT]

I had the stud conversion and ditched it bc it made CF inspections & changes a gigantic PITA. Not a fan at all. That won't matter for much longer anyway bc I have the TSI roller conversion waiting on me to install. Will probably do the cam chain and tensioner while I'm in there.

I only recommend the stud kit because I went K04 over 100k miles ago. Even though I was careful with the 10Nm torque for the bolts(actually only did them at 9Nm, actually did 80 in*lb)...each time I went to loosen them for a CF change, the bolts would pop when they would loosen. Eventually the threads in the cover were all stripped out and the cover is about $700-$800 usd to replace...plus the pain if swapping it. I too found the studs a pita as they were too long. This is why I did a vid showing I cut them shorter for easier hpfp removal, LOL.
The roller conversion is the best option of course.

So you installed the IE hpfp a couple of years ago without upgrading the tune? That's a bit of wear without the reward isn't it? The piston collar nut has seals in it that the piston go through and they wear...usually within 100k miles...my first lasted 90k miles. I see IE says their seals are tough, so hopefully it hasn't mattered. In the next few years we may begin learning more of the IE lifespan from others with it, right?