Noise after fueling changes

[EDIT FIXED ISSUE - solution at bottom of this post]

 

Looking to hear from others who have modified their fuel system.

 

Specifically, has anyone attached braided fuel lines to the stock hard lines and NOT had excessive noise in the cabin resonating through lines? Wondering if 'soft' lines are a must to reduce noise transmittance.

 

 

 

Diagram of the setup pictured above

 

 

I removed the aging stock FPR due to some inconsistent fueling while tuning.

I went with the the STI FPR mentioned in this post:

http://legacygt.com/forums/showthread.php/famous-stumble-fixedi-232816.html

 

That FPR was not a direct replacement and I needed to remove the dampers to make it work. Immediately got that 'water hammer' noise from the injectors that sounds like engine knock in the cabin.

 

Picked up a Radium Fuel Pressure Damper, which took care of the knocking but now I have 'vibrating' coming into the cabin at 2000-2500 RPM. This is my main problem. Most of the fueling issues have been resolved, and the fuel delivery appears smoother and more consistent with the current setup.

 

On the stock setup; Does anyone know about this damper that is after the FPR? Is it possibly a check valve? I can hear the fuel system 'filling up' when I turn the car to ON. Wondering if the OEM system keeps the lines full and my mods have allowed the lines to drain back and empty. As an example, It almost sounds like someone is spraying a pressure washer on the door panel while the lines pressurize.

 

 

Stock Diagram

 

Wondering if I should try to replace that second damper after the return, and if I should replace that hard connection (blue) on the supply, back to a soft push loc type hose.

 

[EDIT - ADDED MY FIX]

 

I changed one thing at a time until the noise was gone. The blue hard connection was not the source. My broken fuel pressure gauge was not the source - swapped in a plug (seen sticking out of the green Radium damper in pic)

 

So the solution WAS the damper between the FPR and the Return Hardline (bottom connection). Was replaced into the OEM location. All kinds of noise went away once I put this damper back in. The pump priming 'spray' sound is gone, the rattle is gone, and the 'air sound' which is similar to the priming sound (when you turn the key to ON before starting).

 

 

Hope this helps someone else troubleshoot their issue. My stumbling issues have cleared up with the OEM STI FPR, I've seen improvements in my logs, but I haven't done a super-scientific isolated 'before and after' to back up the feeling of improvement. The logs show more consistent fueling and was able to set my fuel injector scale closer to the recommended value. Recommended was 3000, the car wanted 3250 to over compensate for low fuel pressure. Now I've settled on 3060, which is giving better long term fuel values (+3 to 5%)

 

I'm just happy to have a fresh FPR in there and be rid of the extra noise - was driving me crazy.

 

Before I changed out the FPR I was at about 35 psi, after I was at about 42 psi. I think this helped smooth everything out. The Radium fuel damper is nice, it took away the injector knocking immediately (water hammer effect). I got the normal range one, not the extended range.

 

For reference - fuel mods are:

ID1000 Top-Feeds

DW65c

Radium Engineering Vacuum referenced FPD

-6AN fuel lines

OEM STI FPR

I have the 04 sti regulator in my obxt i used the thread you referenced as a guide, i also used the xact part #'s for the regulator and fittings, along with some rubber fuel line hose..... I removed the entire stock unit and only reinstalled the 04 sti fpr and a fitting for my snap on gauge. No problems or extra noise.

I also performed said mod. The first time I started the car I could hear pulsing in the car so I took one of the dampers off the old fpr and it went away.

Then awhile later I took the damper out and changed the length of some of the fuel hoses ro clean up the install. The noise is all but gone. It can be heard faintly at idle if you know what to listen for.

I've been running without any dampers and haven't run into any issues.

Thanks for the replies. Good to know you guys removed all those bits as well.

I will keep tinkering with it.

 

Maybe some of my hardlines are not held securely somewhere in there, and some new vibrations are making that evident.

It sounds like they are vibing against the firewall, or in a little deeper under the dash. Haven't looked too hard, but I don't think that is a very easy spot to access.

 

I've seen a few posts on fuel noise, they all seem a little different, but I'll post an update if I get it solved. Thanks again.

Could be some kind of harmonic resonance type if thing...just experimenting with the length of fuel lines could do it.

I mounted mine upside down for ease of install and shortes hoses/cleanest install..

Interesting. Was curious if they needed to be installed upright.

Mine has been upside down for 30k miles no stumble and it runs its ass of 0-60 in 4.6 with a 16g and 5eat ;-)

Op, I've had that issue with mine for a while now...ever since I did the fpr mod.

However, my noise is at idle and disappears around 1000-1500. It is random when it starts and stops, but occurs more frequently when the engine runs longer.

I've noticed that just moving the position of the damper makes a huge difference in the volume and frequency.

I've been running it that way for over a year, it doesn't get worse and I have had no issues with the setup aside from the noise.

I shot this when I first installed to see if it was common. It's hard to distinguish from video but you can hear it cut out at :21 and back in around :28.

Similar noise? It sounds like air rushing through tubing at the engine's pace.

I shot this when I first installed to see if it was common. It's hard to distinguish from video but you can hear it cut out at :21 and back in around :28.

Similar noise? It sounds like air rushing through tubing at the engine's pace.

 

I've since fixed the issue, but..

Yes, it was quite similar to that sound. Hard to tell over video, but I'm pretty sure mine was significantly louder. It actually got a little worse, and stayed that way. It was a couple of different sounds, one was the 'air sound' but louder and the other was a hideous dash rattle, even though everything was tight. Range was larger than I had initially stated as well, about 1500 - 3500 rpm.

 

Going to edit my initial post and add my solution, in case anyone else runs into this oddity.