Turbo PRV racing engine oil tricks
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Thread: Turbo PRV racing engine oil tricks

  1. #1
    Tadpole
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    Default Turbo PRV racing engine oil tricks

    After a dormant period I am trying to test the oil scavenge/pressure system on my racing car. It is up on stands in the shed with appropriate fans etc. I have set up a remote oil tank with a flow meter in the return line, in place of the oil tank between engine and gearbox. We ran a test to try and measure the performance of the scavenge pump and the efficiency, or lack thereof, of the sump pick up, prior to fitting a modified sump and repeating the test.
    We ran it for 30 sec. at 2,4,5 and 6 K RPM then with hot oil repeated test. On the second run we had to shut down after 14 sec. at 5000 as oil pressure began to dive.
    This was consistent with big end failure at Esses hillclimb and falling oil pressure after 3-4 laps at eastern creek super sprint.
    I surmised that to much air was being sucked and the system was not getting rid of it. After various discussions it was decided to instal clear piece of hose in the pump return line. Hose and fittings were found and oil drained from test tank to instal same. THERE WAS ONLY 1.5 lts OF OIL IN THE TANK !!!!
    There had been 8 lts when we started, 6 in the tank and 2 in sump, filter, cooler and lines.
    I then drained the main tank and found 4.5 lts had found its way back there via 2 breathers from rocker covers ! The breather catch tank had a dribble.
    So my question is ; Do I have a problem ?
    The reason for the remote tank is that I can't fit the flow meter in the existing system. Incidentally the flow meter is only good for a vague guide as scavenge pump sends the oil/air through in inconsistent squirts.

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  2. #2
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    Don't really have an answer to the question but I am impressed with your set up to run the test. I assume the pressure oil pump ran a consistent stream of oil till the supply ran out. Quote "as scavenge pump sends the oil/air through in inconsistent squirts." I assume this normal for a dry sump system? Is there restrictors in the breathers from the rocker covers? The restrictors in the breather of a V8 Landrover motor are interesting. They have series of 5 baffles that block the metal outlet on top of the tappet cover with only a small slot on alternate sides of each baffle for the gases to be sucked through. The Reno 15 auto has a small air filter T'ed off the breather pipe that allows some air to be sucked into the breather pipe to reduce the amount of suction on the tappet cover. I am probably right off the track here as modern race engines are really out of my depth. But it's an interesting test set up.

  3. #3
    1000+ Posts Frans's Avatar
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    My worth. I think that you have to much sump/crankase compression.

    I have experienced it in a n/a Renault 5 engine when it was running with broken rings. Drive it at 100km/h for kms on end with no issues but don't go any higher then the oil can't return due to the sump compression air rising through the oil draining route causing the oil not to drain into the sump. The level in the rocker cover rises until it reaches the breather and then suddenly the car would loose power with a huge plume of smoke out of the exhaust and then repeat this with short intervals (this is where your oil goes as well but through the breathers to the breather tank). This engine had the new type 1300 block where the only drain was out front of the cambox at the timing gear end. Older blocks had the drain holes at 1/4 way and 3/4 way in the cambox and the drain was much better.

    I also experienced it in a turbo charged Gordini engine that I built but in this case the turbo oil drain back into the sump was hampered under high boost and because this big dia drain line was used as a sump breather as well, the escaping sump compression re-directed the turbo drain oil back into the breather tank.

    I hope this can add to your thinking because in my caseboth instances where sump compression, 1st due to broken rings and then 2nd to high boost changing the drain flow direction.

    Regards, Frans.
    Bustamif likes this.
    Old enough to know better
    Young enough to do it anyway.

  4. #4
    COL
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    A simple leak down test should prove Fran's theory which is very plausible.
    Regards Col

    1973 Renault R12 Station Wagon
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  5. #5
    Tadpole
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    Thanks Sunroof, Thank you for your interest, this is not really a modern race engine.I may have been a little unclear in my description. The dry sump pump has 3 stages, 2 for scavenge and 1 to supply oil back into engine. The flow meter is in the scavenge line and I am hoping to reduce the amount of air with the new sump. Hence the test, trying to be at least a bit scientific. This breather problem needs solving so thanks for your input Cheers Geoff

  6. #6
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    Hi Frans and Col, Thanks for the ideas. For the sake of this test I can tee in a line from main oil tank to the suction line. At least I can compare sumps, then adress the crankcase issue. The sump has two shallow dishes cast into it with a hole bored in to each from the side, then lines going to pump. The modified sump has tubes with ends blanked off and slots milled in underside fastened into the holes. The aim obviously to suck more oil, less air.
    Thank you both for your interest.

    Regards, Geoff.

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