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Neil Harvey Neil Harvey is offline
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Join Date: May 2004
Posts: 406
Originally Posted by boosted79 View Post
You are assuming the stock pump gets a 100% "fill" of the volume between the gear teeth. If it does not, and porting the intake of the pump increases the "fill" then it will pump more oil. Same as porting a head increases the VE and the air the engine will pump.

If the pump doesn't fill the inlet volume completely it will pump air and you will have immediate bearing failure. A large % of the supply oil is bypassed back into the inlet side via the relief valve. The oil tank contains a large volume of oil and that oil has a direct path from the bottom of the tank into the inlet side of the pump.

The pump is under driven just over 50% and to see any cavitition the gear speed has to go up way beyond any engine speed these early engines ever need to run.

The GT3 pump has a slightly larger pressure gear diameter than the scavenge gears but we know that at 9000 RPM we have not seen any cavitition with this pump.

When opening the inlet port to the pump or the exit side of the pump has made no difference to flow in any testing we have conducted. I have read where some mod to these pumps increases flow by 15-20%, an increase we have never seen.

Once the cavity between the pump teeth is full of oil, your ability to pump more oil is based on pump speed only. What is moved from the inlet side to the exit side has to exit the pump otherwise the pump would explode under hydraulic pressure.

The pump, pumps against the relief valve to establish the running pressure, so any "pressure' the pump produces to push the oil out through the exit hole will lower the work the engine has to do to turn the pump. This is the only gain any mod to these pumps could net.

However, what is an issue is the aeration of the oil. The scavenge side is gear type which pumps air and oil and churns this into a milky mix that never gets a change to excavate the air from itself in the tank before entering back into the engine. We have found that running a lower viscosity oil in race engines helps to lower this problem.
Old 09-30-2017, 02:38 PM
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