CP3x2, race valve or shimmed fprv?

Harbin_22

Active member
Dec 4, 2010
3,858
7
38
Southern Indiana
I want to bottle test the fprv, do I need to just plug the line from the "T" and bottle it from the fuel block. Will it be the same kinda test results? Is it necessary if I am holding rp fine? The only log I have done had the fprv in with 40% @ 2100us was within 200psi. Is that about right, or should it be right on?
 

carter_44

...
May 11, 2010
575
0
0
AZ
My stock FPRV was opening on WOT runs so I did the PPE race valve. The name is misleading as it is not a valve at all but a plug. So, it has its benefits of not letting rail pressure release on hard runs but there is no safety valve to release rail if necessary. Running dual CP3s I would want to shim if possible. If your FPRV isn't opening on WOT runs then shim will work fine. If it is already weak you may want to race valve or get a new FPRV and shim it. I didn't worry much about the shim on mine as I am running stock fueling with lift pump only and didn't figure I was going to spike pressure enough to cause problems but you never know.
 

PureHybrid

Isuzu Shakes IT
Feb 15, 2012
3,492
472
83
Central OH
A shimmed FPRV over time can weaken to the point where fuel gets past it... Ben has proved this

He is probably right, but Bosch put the safety valve there because of a potential hazzard. I'll keep my shimmed valve with a "weakening" spring, I have a spare shimmed one in the tool box anyways :thumb:
 

Kennedy Diesel

New member
Mar 13, 2009
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I want to bottle test the fprv, do I need to just plug the line from the "T" and bottle it from the fuel block. Will it be the same kinda test results? Is it necessary if I am holding rp fine? The only log I have done had the fprv in with 40% @ 2100us was within 200psi. Is that about right, or should it be right on?


Remove the U shaped hose from the port on the rail itself. Plug the hose as this would now be open to main return fuel. Add a hose to the nipple on the rail and go out and beat on it a bit. Should not discharge ant more than what was standing in the nipple.


What if the plating ever flaked off? Shimming is under about 50 cents total vs 35 bucks. Thats the reason I did it.

Cheap, simple, effective to shim it




A shimmed FPRV over time can weaken to the point where fuel gets past it... Ben has proved this

I see no merit to this statement UNLESS you are exceeding the shimmed pressure and activating the valve. It is my opinion that the springs weaken due to the excess heat of the fuel flowing through the valve.


He is probably right, but Bosch put the safety valve there because of a potential hazzard. I'll keep my shimmed valve with a "weakening" spring, I have a spare shimmed one in the tool box anyways :thumb:


Well said. With the set pressure raised severel thousand psi above stock (shimmed) the valve should never actuate. If it does it is due to a pressure cycling issue either caused by a shortfall or regulation issue.
 

x MadMAX DIESEL

<<<< No Horsepower
Dec 30, 2008
7,535
1
38
34
Lexington, Ky
I wouldn't shim it even until you start popping it often. Llys were the trucks that really had trouble blowing them open.

Sent from my PC36100 using Tapatalk
 

Kappa9012

MAN.... I Broke it again.
Aug 5, 2008
694
0
16
Peoria Il
if you're not dropping rail with a shimmed valve then why go plugged... i'm not a fan of having a diesel filled pipe bomb under the hood of my truck..