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  1. #1
    ABBOTT's Avatar
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    RRFPR Psi Gauge vs Riva Rail Gauge Readings

    Readings on the Riva Rail are consistently 5 psi less than Regulator Gauge.

    Is this normal and should I set 58 psi to the rail reading or to the Regulator reading?

    58 on rail gives me 63 on Regulator and 58 on Regulator gives me 53 on rail.

    Thanks.
    Last edited by ABBOTT; 04-07-2017 at 07:42 PM.


  2. #2

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    I have a problem with this to I think Riva gauges are cheap I had bought a inline I put right before rail and the fpr said 47 and the inline said 58 even switch gauges and same thing and even put 2 Riva gauges and same so I would buy a nice oil filled and use that and believe that one I don't ever trust the Riva reading

    Again buy a nice oil filled and use that psi as your setting

  3. #3
    ABBOTT's Avatar
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    Well I think they are the exact same gauges since the Regulator and the rail both are Riva's.

    I'm just wondering if the drop at the tail end of the rail is normal since fuel is flowing in three places before that point.

    If that's the case then I'm thinking as long as I have 58 being pushed at the Regulator side, then that achieves the needed pressure for the Injectors to flow at a given rate and never come up short (like slurping through a straw) based on what the ecu is telling the Injectors to load and be fired per the tune specs. Because when I simply press the start/stop one time (activates fuel pump) but not crank, they both read almost dead on.

    I could be wrong in my assumption though.

  4. #4
    JT jpt7779's Avatar
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    IMO your hose routing is the issue. I assume you have the routing like this: tank to RRFPR to rail which has dead end gauge on the rail end, correct?

    A much better solution to avoid the issue you are having is this: tank to front of rail, end of rail then flow to the RRFPR. This keeps constant pressure through out the rail evenly to all 3 injectors.

    RRFPR return to tank is the same on both configurations.

    Simple solution that works great, especially on high boost, high rpm setups.

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  6. #5
    ptscon's Avatar
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    Quote Originally Posted by jpt7779 View Post
    A much better solution to avoid the issue you are having is this: tank to front of rail, end of rail then flow to the RRFPR. This keeps constant pressure through out the rail evenly to all 3 injectors.

    If pressure is 58 PSI at rail exit after passing 3 injectors, wouldn't that mean pressure at entry must be higher?

    #3 would see the highest and consume a bit, #2 lower and consumes a bit, #1 lowest and consumes a bit ...with end result 58 psi

  7. #6
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by ptscon View Post
    If pressure is 58 PSI at rail exit after passing 3 injectors, wouldn't that mean pressure at entry must be higher?

    #3 would see the highest and consume a bit, #2 lower and consumes a bit, #1 lowest and consumes a bit ...with end result 58 psi
    The injectors open sequentially, not all at once. But yeah, there is a pressure drop.

  8. #7
    ABBOTT's Avatar
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    Quote Originally Posted by jpt7779 View Post
    IMO your hose routing is the issue. I assume you have the routing like this: tank to RRFPR to rail which has dead end gauge on the rail end, correct?

    A much better solution to avoid the issue you are having is this: tank to front of rail, end of rail then flow to the RRFPR. This keeps constant pressure through out the rail evenly to all 3 injectors.

    RRFPR return to tank is the same on both configurations.

    Simple solution that works great, especially on high boost, high rpm setups.
    You are correct and I forgot that you've sent that routing to me before. I will change it up. Not worth the risk imo. Thank you sir.

    Surely others have seen this issue that have the routing like this (which is the way Riva instructs it in their directions). Or maybe not because most don't use two gauges - which is the only reason I caught this.

    Could be dangerously lean in some areas for those that run on the edge. Or flat out confusing because someone can see 58 at at RRFPR but see AFRs too high and throw more fuel at it via the map to compensate.......your suggestion (JPT) eliminates that whole issue via rerouting and putting the RRFPR after the rail. Totally forgot about that.

    Thank you again.

  9. #8
    JT jpt7779's Avatar
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    Your welcome. Realize that with this looping setup, it is completely normal to see the pressure drop after shutting off the engine, as the fuel returns back to the tank from the FPR.

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  11. #9
    ABBOTT's Avatar
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    10/4 Roger that. Appreciate it. Fixing now.

  12. #10
    JT jpt7779's Avatar
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    Here is my setup and I don't have a pic of Riva RRFPR, but it has a fuel pressure sensor on the left (Motec logging), the hose from the back of the fuel rail on the right, and the return to tank on the rear. Small stone filter and rising rate to the Wilson Intake Manifold. Set to 58 psi.

    Lambda/ AFR and EGT's are rock solid consistently with this setup. Simple and works - Thanks Evan Kassing!!
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