Jump to content

PRV and Fuel pipe resonance


Recommended Posts

Trying to get rid of the dreaded resonance, as cheaply as possible.

However there seems to be some conflicting info on the various suppliers websites.

Firstly i've seen that changing the existing (cloth braided pump) to PRV pipe for a rubber one, could cure this but could lead to petrol smells in the boot.

  • Anybody fitted, or has a, rubber pie and experienced petrol smell and has it cured resonance?

Secondly, Some sites say supplied ready to fit others say the unit  needs to be calibrated with a gauge.

  • Anybody fitted a Diaphragm PRV straight out the box without the need to calibrate.
  • Was the new PRV a direct replacement or was additional pipework required 

Currently have Bosch pump (TR Shop), new pipe work, refurbished PRV, MU etc.

Thanks

Dave

Link to post
Share on other sites

Dave. 

 

Prestige (Malcolm)’s diaphragm prv is preset to the right psi straight out of the box.  I’ve just asked him the same question!  He says it’s a straight bolt on job.

 

cheers

 

dave

Link to post
Share on other sites
8 minutes ago, cookie said:

Trying to get rid of the dreaded resonance, as cheaply as possible.

However there seems to be some conflicting info on the various suppliers websites.

Firstly i've seen that changing the existing (cloth braided pump) to PRV pipe for a rubber one, could cure this but could lead to petrol smells in the boot.

  • Anybody fitted, or has a, rubber pie and experienced petrol smell and has it cured resonance?

Secondly, Some sites say supplied ready to fit others say the unit  needs to be calibrated with a gauge.

  • Anybody fitted a Diaphragm PRV straight out the box without the need to calibrate.
  • Was the new PRV a direct replacement or was additional pipework required 

Currently have Bosch pump (TR Shop), new pipe work, refurbished PRV, MU etc.

Thanks

Dave

Hi Dave!

This is my experience based upon 37 years of Bosch pumping. I am not convinced by some of the PI specialists who use a solid PTFE hose rated at 1000 psi from pump to PRV which gives the dreaded harmonic hammering and you have to use one of his PRV's' to cure this problem,he is based in Wales??????. My system is based upon info that I was told by a Bosch engineer in the 1980's. He told me the pump type to use and the Bosch pre- filter type + the bore size of pipework from tank to pump and the type of high pressure hose pipe and rating to use. Bosch pumps need a flood supply of petrol, nothing less than 3/8" bore certainly not 1/4" as original. The hose that I am now using is the Gates type' Barricade Fuel injection rated at 223 psi WP, which is fully flexible and has never shown any signs of harmonic hammering or its predecessor. The Gates hose is fully ethanol resistance to 85%. If you want more info PM me.

Bruce.

 

Link to post
Share on other sites

The resonance is caused by the PRV plunger moving in and out at high frequency with this frequency coinciding with the resonant frequency of the fuel piping - more likely to happen with old piping that has gone stiff or braided piping which is oftern inherently stiffer.

Sometimes twisting or flexing the highpressure line between the pump and prv can be enough or swapping to a different length pipe may help.

The diaphagm PRVs are seemingly less prone to this affliction. My experience with them that although notionally set at the right pressure out odf the box, my 6 misfired at full throttle & 5000+rpm. When I checked it the pressure measured at teh metering unit (which is where it is meant to be measured) was 95 psi. Easily adjusted to 105psi. The diaphragm PRVs can be adjusted without petrol leaking everywhere - unlike the the Lucas PRV which is adjusted through the end with the PRV to tankl return rremoved which results in significant fuel spillage if you do it with the pump running. (you could do it with the pump turned off, reconect and check & repeat until you get it right)

I did experiment with a chaepo diaphgram PRV (£18) sold as an after market one for the Nissan 3000z from eBay which performed fine, but swapped to one of the "proper" diaphragm PRV's prior to a long continental journey.  Had to get a few plumbing adaptors but it worked well enough. The only gremlin was that the £18 prv came with a free pressure guage which blew apart when subjected to 100+psi. However once blanked of it was fine.

Link to post
Share on other sites

Dave,

I have the same Gates Barricade fuel injection hose Bruce uses.

I was not able to source a ready to fit pipe, including fittings, so ordered the Gates hose which I had pressed with ferrules on my existing fittings in a local hydraulic hose shop (the shop will supply the ferrules). 

I ordered a new item from Moss about 1 year ago, but that was made with hose from the wrong quality (to my opinion); I have provided Moss with the relevant data, not sure what hose they use now but I think they appreciated the input and changed the hose type.

Waldi

Link to post
Share on other sites

Changed my fuel lines to Gates Barricade and installed a loop in the return line to the tank - got rid of the smell and resonance. I set my PRV with  compressed air and  the PI system  operates now correctly.

Link to post
Share on other sites
  • 2 years later...

Since ‘completing’ the 4 year restoration of my 5 I like many others had an horrendous hum from the rubber hose exiting the Moss Bosch type pump with pre filter, standard prv fitted on the chassis with pump in wheel arch. The noise could be heard about 20 yards away with the engine running! Read all sorts of remedies but decided to start with the simplest and cheapest options to see what happened.

I decided to maximise the fuel flow from the tank, so bought a big bore exit union from tank to filter, from Carl at TR Trader. I binned all the banjos and replaced with appropriate straight or elbow unions. Changed the hose between the filter outlet and pump inlet from a 90 degree arrangement to a curved route.….. and RESULT!  All I can hear now is a wonderful exhaust note. BTW I did also have an in-line tap between tank and filter which was also reducing flow.

Happy days,

Tim

 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.