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I have read here and some other posts about the porting/modifying these Oil pumps which increases the flow.

I'm confused how this increases the flow rate? The two parts of these pumps that can affect the oil volume out of the pump is the pump housing internal condition and the gear end clearance?????

Interested to hear how this is increased.
Old 09-23-2017, 08:15 PM
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Quote:
Originally Posted by 82 sportsc View Post
higher pressure forces Oil In gaps and moving parts that have tight tolerance .

With out pressure wouldn't we just have oil laying on the outside of parts ?

Frank
Not really you only need pressure to allow oil to enter the bearing - once the oil is in place the separating forces are created by the rotation and the pumping action of the bearing itself.

http://kingbearings.com/files/Engine_Bearings_and_How_They_Work.pdf

I would tend to agree that Porsche must have some reasons why the changed design and altered the ratios of scavenge and pressure as they changed the engine.

I am just not convinced that a 2.2T needs a Turbo or GT3 Pump even when it is modified to with E Cams and S pistons and this is what is being prom0ted in the UK at least. For the majority of engines the standard pumps seems to more than adequate.

I don't understand all of the reasons for the changes that Porsche made and not all of them seem entirely consistent as the flow requirements don't change much.

I really do fail to understand how porting a gear pump increases flow and without specific test data I will remain sceptical.
Old 09-24-2017, 01:21 AM
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Chris
You are a brilliant engineer and always enjoy your thoughts.
I did read the post on engine bearings and how they work.
My immediate thought goes to the IMS issues for several years of Porsche Engines ...including my 2000 Boxster.
The article notes the big issues are
-Oil starvation with high load (extreme would be no or low oil)
-low rotation speed (low RPM's ....hence no pressure )
-low viscosity ( thin oil easily squeezed out between components)
-elevated temp (decreases oil viscosity)

So the simplicity is........we need more oil capacity, higher RPM's , higher oil viscosity and the ability to keep the temperature of oil lower.
Also any effect to reduce the creation of air from moving parts which reduces viscosity and increases heat ....Air will heat faster than oil (I think?) and also replaces the oil film surfaces with air so less oil and increased metal to metal contact and wear.

Since our engines have a fixed oil capacity the variables we can change that will .....reduce wear to engine components hence reduce possible failure and longer life are basically controlled by the oil pump, the oil and any modifications that will reduce air mixed in oil ,lower temperatures of components, increase viscosity ( only to a point based on temperature ) improve flow and pressure to an optimum .
So an efficient oil pump that reduces air and improves flow at low RPMS and creates more pressure seems like a good thing.

That seems to be what Porsche has done ( not sure given the IMS problems ...but it's generally accepted that low mileage engines that sit and are driven like little old ladies (low RPMs ) and others are doing with their redesign of older pumps .
I am trusting that those re-engineering old style oil pumps are addressing the basics of undesirable effects.

But Chris you are correct that real proof is needed....but seems many of the ill effects are controlled by the driver .......oil type/capacity, RPMs and oil cooling. But engineering of pumps and engine components should be able to adresss other nasty effects.

Chris ...get work on these !
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Last edited by 82 sportsc; 09-24-2017 at 07:10 AM..
Old 09-24-2017, 07:07 AM
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"""I really do fail to understand how porting a gear pump increases flow and without specific test data I will remain sceptical. """

Chris,

I too do not understand how porting these pumps increases flow. My understanding is, there are 3 factors that can increase flow. Gear diameter, number of teeth and pump speed.

Lowering any restrictions would decrease the work done by the engine to turn the pump and may result in adding that work to the crank output.

This is another area of "engineering by mythology" the Porsche world has live by for years and continues to.
Old 09-24-2017, 09:42 AM
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Installing a larger pump will not hurt the running of any Porsche engine, it may increase the work done to turn that pump.

These engines need twice the scavenging that even the largest Porsche pump has, but real estate dictates the size of the pump that can be installed. The supply side of the smallest pump is well within the biggest engines requirement.
Old 09-24-2017, 09:45 AM
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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.
Old 09-30-2017, 06:36 AM
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Quote:
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.
Does this mean that at high rpm that a 911 pump will cavitate as this is the inevitable consequence of a restricted inlet port when considering gear pumps.

If you don't fill the pump due to a restriction then the pressure in the cavity will fall and ultimately the oil will start to evaporate and this will damage bearings very quickly.

The restriction to flow will also be engine speed dependent so high revving engines will be more significantly affected.

If you consider a typical gear pump with a delivery of around 100 l/min the inlet port size would typically be around SAE-12

if the inlet size were -16 then the pump size would be closer to 180 l/min delivery.

Last edited by chris_seven; 09-30-2017 at 08:20 AM..
Old 09-30-2017, 08:17 AM
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I don't know. But the only way to increase the capacity of a positive displacement gear pump besides turning it faster is to increase suction pressure or decrease discharge pressure. Maybe they open up the discharge ports or a combo of both. I would like to see what they do.
Old 09-30-2017, 02:23 PM
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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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I agree, that's why I would like to see what they do.
Old 09-30-2017, 02:55 PM
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Reduscng oil viscosity in gear pumps dpes tend to reduce flow as the 'thinner' oil is more likley to spill though the mesh but this is probably of little consequemce in practical terms.

The aeration problem is interesting and I think replacing the scavenge gear pump with a Roots design - as used by Autoverdi - helps this probelm.

Measuring the air trapped in the scavenged oil is quite difficult and beyond the scope of day to day testing.

We did produce a test rig to do this type of measurement about 12 years ago, for a leading F1 engine team, and it was used right at the end of of the old V10 era but was also used for the V8 programme.

We used a capacitive measuring technique that prodcued an accuracy of around 1% at a sampling frequency of around 1Hz and it was used to provide the basic data needed to model seperators.


The best way to reduce parastic losses, howver, is to use variable displacement pumps similar to a traditional swash plate design.

Modern VAG pumps which are Gerotor type with the outer rotor controlled by a ring which is allowed to move and is controlled by a spring that adapts the flow to to maintain a constant pressure.

There are also vane pump derivatives that provide a similar capability.

If most modern pumps are being designed with a varaible displacemenrt the Porting pumps to increase flow just seems a little pointless.

Last edited by chris_seven; 09-30-2017 at 03:37 PM..
Old 09-30-2017, 03:34 PM
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Originally Posted by chris_seven View Post
Reduscng oil viscosity in gear pumps dpes tend to reduce flow as the 'thinner' oil is more likley to spill though the mesh but this is probably of little consequemce in practical terms.

The aeration problem is interesting and I think replacing the scavenge gear pump with a Roots design - as used by Autoverdi - helps this probelm.

Measuring the air trapped in the scavenged oil is quite difficult and beyond the scope of day to day testing.

We did produce a test rig to do this type of measurement about 12 years ago, for a leading F1 engine team, and it was used right at the end of of the old V10 era but was also used for the V8 programme.

We used a capacitive measuring technique that prodcued an accuracy of around 1% at a sampling frequency of around 1Hz and it was used to provide the basic data needed to model seperators.


The best way to reduce parastic losses, howver, is to use variable displacement pumps similar to a traditional swash plate design.

Modern VAG pumps which are Gerotor type with the outer rotor controlled by a ring which is allowed to move and is controlled by a spring that adapts the flow to to maintain a constant pressure.

There are also vane pump derivatives that provide a similar capability.

If most modern pumps are being designed with a varaible displacemenrt the Porting pumps to increase flow just seems a little pointless.

Absolutely. The gain is also lowering oil temperature for obvious reasons.

The roots style gears not only help with the oil but are far more efficient creating a vacuum due to the larger area that vacate.

With our involvement in "Jeff's home built" project, we have new pump root style gears coming for these older pumps. As luck happens, the scavenge gears in the later GT3 pumps are the same diameter as the early pumps so these new gears will fit all pumpS up to 997.
Old 09-30-2017, 04:59 PM
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