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Neil Harvey Neil Harvey is offline
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Join Date: May 2004
Posts: 241
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, 03:59 PM
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