Oil pressure drops as rpm rises

Discussion in 'PSI Superchargers Tech Questions' started by Winr, Oct 12, 2020.

  1. Winr

    Winr Member

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    This issue just arose. As the RPM increases my oil pressure drops. I hadn't noticed this until this past weekend. But it follows a recent oil change. We put oil and a new Filter (HP 6) In the motor prior to our last outing. When we fired it up at the shed we had low to no oil pressure. We pulled the mag and primed the pump and then had the typical 80 psi at idle. On my last pass at the track (1/8 th mi) the pressure went away at the end of the pass ( aborted 6.70 run). Got it back to the pits, looked
    It over and fired her up...80 psi at idle but pressure dropped as we brought it off idle. It would return to 80 psi at idle. As this hasn't been seen prior I dont think its a pan to pickup issue but possibly a bad filter. Anyone have a similar experience with HP6 filters? Or other thoughts?
    Combo is
    KB Hemi block and cast pump
    10 qt Brad Penn(Penn Grade) Nitro 70 (8 qt in pan 2 qts lines and filter)
    Dual baffled Dragster/ Funnycar pan
     
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  2. Templar Motorsports

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    Are all your fittings tight? I had this happen to me once. Oil presser fine at idle. But as the RPM came up it would start to loose pressure. Ended up that I didn't have a line tight enough and started sucking air. It was tight enough an idle but ton enough at higher RPMs.
    Just a thought for you.
     
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  3. Winr

    Winr Member

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    I have yet to look but thanks for the bullet point on the check list.
     
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  4. jay70cuda

    jay70cuda Active Member

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    I've had small particles get stuck in my oil psi bypass and held the bypass open.
     
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  5. Blown5402

    Blown5402 Member

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    And check your oil suction line from the pan to the oil pump too. Mine would have perfect oil pressure in the shop and in the pits, and start it up, do a burn out and go low.
    Get back to the pits and it was fine, but found the suction oil line was sucking together later under higher pressure conditions and loosing oil pressure-Jim in TN
     
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  6. Winr

    Winr Member

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    Thanks
    Yep.. tonight we're going thru the oiling system and hose condition is on the list.
    When we had the oil pump drive issue (broke the mag drive slot) we had the pump off so it could be related but all oil system components are going to be inspected.
    I asked abut the filter due to a post I saw regarding using a coarse screen filter with the heaver weight (70wt) oils. This was with regard to similar condition to mine with the fine screen.
     
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  7. vwsamba

    vwsamba Member

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    Sounds like the collapsing line but also seems like you don't have enough oil and it's too thick. I would never use afram filter. Seems like most use the system 1 reusable filter.
     
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  8. Ray Hadford

    Ray Hadford Member

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    Suction stainless braid lines can be sucked flat. The internal rubber hose collapses. The only way to test is under significant vacuum and that is not reliable.

    Earls sells spring material for the larger line sizes. It is very low cost and prevents collapsing. I bought some from Summit.

    I have known of both fuel and oil lines without an internal spring collapsing. I run them on all suction lines.... oil and fuel.

    Will can add to this.. The hose he sells may not have this problem.

    Ray H.
     
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  9. Mike Canter

    Mike Canter Top Dragster
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    I agree with Ray. Most likely a hose collapsing.
     
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  10. Winr

    Winr Member

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    We went thru the system and found a fitting or two that could have been tighter (not loose but got half a flat tighter). 80 psi at idle and now only 5 psi Drop in pressure as rpm (5000rpm) so something is going on, Today was my last chance to get out this year so the engine is coming out this week and give it a once over.The comments on hose collapse got me thinking...Just got over the headache... I use a static dual line pickup. The screen is perforated .0625" steel (hole size unknown at this time) so what are the suggestions on hole size and pan to pickup clearance...there is potential that the screen and/or the pickup is being sucked to the bottom of the pan.

    Thanks for all the replies.
     
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