fpr question

[alan b]

ok do ive got a new for finaly, it s an in line one. but i have no blanking plate for the rail, but if my std reg is 2.5 bar and i want to run 3.5 bar, can i just leave the old one on? as the new one after it will be holding higher pressure anyway? or is there something totaly obvious im missing here!?

[GRUNT 16V]

Ehh???

[Paul]

no it will hold 2.5bar at the rail then 3.5 bar from the rail to the new fpr. so effectively be a complete and utter waste of time and effort. Buy a blanking plate, chirs astley sells them i think, or eBay has them on.

Paul

[meritlover]

no it wont,
if the return is fitted after the 3.5b reg then the back pressure will be at 3.5b in the fuel rail. because the std reg is set a bar lower, it will be wide open trying to dump as much volume as it can to the return. so essentially its doing nothing more than a piece of pipe. but the pressure should be be 3.5

[16v Nova Kev]

or is there something totaly obvious im missing here!? spelling for a start lol

[Paul]

no it wont,
if the return is fitted after the 3.5b reg then the back pressure will be at 3.5b in the fuel rail. because the std reg is set a bar lower, it will be wide open trying to dump as much volume as it can to the return. so essentially its doing nothing more than a piece of pipe. but the pressure should be be 3.5

Are you sure?

[meritlover]

yes. think about it

[meritlover]

if you have an OE regulator with a return to the tank and you were to plug the return. the pressure would shoot up to match the discharge of the pump regardless of what the reg was set to.

its the same thing when fitting a higher pressure regulator downstream of the OE one.

[16v Nova Kev]

i dont get it does is the oe not restrict it to 2.5

[alan b]

well think about it a 2.5 bar reg and a 3.5 bar reg are just like two restricters, and the 3.5 bar one just restricts more? i mean the 2.5 bar one will stay open because the pressure in the return after it will be 3.5 bar ? therefore making the pressure in the rail 3.5 bar?

[meritlover]

i dont get it does is the oe not restrict it to 2.5

it doesnt restrict it to 2.5, it 'vents' to the return at 2.5 (a bit like a relief valve) it controls the back pressure in the fuel rail not the pressure going into it.