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Oil pressure (Fact vs Fiction)

Discussion in 'Diagnosis/Help' started by Stig, Apr 17, 2009.

  1. Stig

    Stig ST162 Guru Donated!

    This is another of those topics surrounded in smoke and mirrors!

    High oil pressure is not necessarily a good thing
    1) It could mean that oil is not flowing through the motor
    2) The oil pump is wasting large amounts of power to pressurize the oil.
    3) The motor and oil may not yet be warmed up properly
    4) The oil pump relief valve could be jammed

    Myths
    Contrary to popular belief, race engines DO NOT have tighter clearances or run at higher pressure -Race engines have looser clearances to cut down on friction and flow more oil through the bearings - helps clean them and cool them.
    Adding xyz to the oil will give me more power - because it says so on TV!
    A special oil filter " " " " "

    Fact
    White metal bearings work properly at around 30-40psi - anything more is wasted energy.
    One reason race engines idle so high is to try and keep pressure to the bearings, at normal idle they will seize up!
    At 10 000 rpm they will only make around 30psi of oil pressure, and save the extra power for the wheels.
    Race engines also have a warning light on the dash set at around 10psi, which I think should be a feature on all cars. Forget 2 rev counters, voltmeters etc
    A hard working engine can generate oil temperatures as high as 160 deg/C, the exhaust will glow red above 900 deg/C.
    The viscosity (thickness) of the oil reduces greatly with an increase in temperature.
    3S motors are known to have a problem with oil surge, ie sloshing around,
    when that happens the oil pump sucks air and pressure is lost which causes bearing failure.
    A good tip is to keep your oil level slightly above the full mark.

    When the sender fails or the feed to the gauge is disrupted, it will show a high reading and not move around as normal

    Mineral Oil
    Normal Mineral oils break down at temperatures higher than 120 deg/C.

    Synthetic oil
    Synthetic oils have a higher working temperature and are made to withstand temperatures in excess of 160 deg/C.
    The change in viscosity is also not as great as with mineral oil.
    Synthetic oils available to the public are not true synthetic oils, they are blends of mineral & synthetic. True synthetic oil is only available to top race teams and the aviation industry. They do not make a motor make more power but do enhance reliability.

    Additives
    Generally speaking they are a waste of time & money, there are stories up the wazoo about miracle additives and I've heard most of them.
    However I have seen one product, "Prolong" make a significant difference (15hp) on the dyno in a race car engine & box. It did also lower the running temperatures slightly. Unfortunately it is not available here in NZ & there may be others capable of doing the same.
    There is an additive "seal restorer" which can soften hardened seals and prevent leaks and smoking, it does work, but takes weeks before any effect is seen.

    Engine bearings
    Which type do I use?
    Truth is it shouldn't make much difference - If the clearances & pressure are correct.
    The journals run on an oil film and the bearings are "shims" used to adjust the thickness of the film and also absorb any filings or dirt that can't travel in the oil film out of the journal to ultimately be absorbed by the filter.

    The bearings will only rub if the oil film breaks down (faulty oil pump, crap oil, blockage etc), large pieces of junk become jammed between the journal and bearing shell (dirty motor, faulty filter) or the rod pressure overcomes/squashes the oil film (detonation, NOS/turbo/nitro etc power increases) or almost unheard of - a fracture in the bearing shell.

    I've seen many cases where used bearings were fitted into race motors in an emergency and went on to outlive the other "new" bearings. We also often used old bearings to get that extra thou or two which often makes the difference between average and freak motors.

    Bearings are a good way to "read" what's happening inside a motor and all top race teams have their oil analyzed as well to determine where/what wear is taking place.

    Tips
    When installing a fresh engine, always prime the motor by putting a drill & 12mm socket on the oil pump and spinning it with the oil pressure sensor removed. Oil should shoot from the sensor hole, replace the sensor and spin it again to lube the cams.
    Before starting the motor, remove the spark plugs and disconnect the distributor. Spin the motor while watching the oil pressure gauge. If it does not move normally - DO NOT START THE ENGINE, find the fault and rectify it before you wreck the internals.

    When starting a cold engine, let it idle for a minute or two - why?
    Pistons, bearings, cams, pumps, heads, blocks etc are made from different metals and need time to expand and warm up to their normal operating temperature.
    Surest way to wreck any engine is to start it up and rev the crap out of it.
     
  2. Puffie40

    Puffie40 Guest

  3. Stig

    Stig ST162 Guru Donated!

    I don't believe in "breaking in", we never had the time to break race engines in "properly"
    and there was no difference in the motors that were broken in according to specs.
    An engine breaks itself in, in the first 30 min of running
    In actual fact I found that motors that were broken in quickly and driven hard from the begining
    made more power and revved better than "normal" motors, provided I followed the following
    guidelines

    My method (many will argue with me, it's your car!)
    1) Use a cheap 20/50 oil & decent filter (thinner oils break down faster, depends how cold it is outside)
    2) Prime the motor up to pressure before putting the cambelt back on (a drill on the oil pump)
    3) Spin the motor minus spark plugs to check pressure is correct and circulate oil
    4) Start the motor and let it idle for 5min (lets pistons & bearings etc expand)
    Listen carefully and shut it down if any strange noises appear - fix the noise before proceeding!
    Do not rev it for at least 3min!!
    5) Let it cool for 30min - check for leaks
    6) Start it again and let it idle till the fan kicks in (makes sure the water isn't leaking etc)
    7) Let it cool for 30min
    7+1) Start it, let it idle till warm and go for a gentle drive
    9) Use it normally, not gunning it and letting it warm up first for 100-500km
    10) Drain oil, change filter, remove & clean sump (only way to get rid of all filings)
    11) Fill with quality oil
    12) Spin without plugs till pressure is correct
    12) Use as normal
    13) Do not add any oil additives for at least a few thousand km
    14) Change oil & filter when it turns black or every 6 months (oil builds up acids which eat bearings).

    That was taught to me by a factory Honda Superbike Racing mechanic in the 70's
    I've been doing that for 30yrs and haven't broken a motor yet, once I had a big end start
    rattling on the first 5min warmup and it was changed in time to prevent further damage.

    It's important to understand that metals expand when they heat up, different metals expand
    at different rates and it takes a few minutes for the motor to "settle".
    Your motor parts are designed to work together at operating temperature (80-90 degC)
    Gunning it before everything is at operating temperature will damage whatever has not yet
    expanded fully (usually the bearings)

    Do that every time you start your car and it last far, far longer and make more power than
    the guy who revs it while cold. In fact you should never drive a car till it is fully warm
     
  4. Alexg

    Alexg Well-Known Member Donated!

    Regarding pressure sender.
    Gen1 3sge when the sender is disconnected it reads zero pressure, not high.
    Mine came off once and I had a heart attack as it was showing nothing when I was driving.

    Cheers for the info, as always. Good help
     

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