Oil Pump Question?

[Neil Harvey]

Is this a mod that is typical? Customer said it came from company that sells this mod.

Opened it up and found this along with high end clearances?

Really poor workmanship. Maybe this is a one of ? Not quite sure what the idea of this is and what it will gain with this type of pump. Looking for information on what this does and any data that supports this mod.

In case I'm missing something, any info is welcome as I am trying to understand what this does. And is this the normal quality of workmanship? Not trying to find fault, but an Oil pump is an important part of any engine and this seems really poorly done.

[Henry Schmidt]

What you're looking at is a rudimentary attempt to increase oil flow by porting the inlet and outlet port flow characteristics.
We've been doing similar, although admittedly more elegant versions of this modification since the early IMSA days. It is one of the machine shop services we offer.
Back in the 70's, there were very few options in the way of pumps so improving what we had was paramount. In the early days we did the porting by hand but now we use a fixture in the Bridgeport using a ball end cutter. Interesting enough, Porsche factory started employing these techniques in later turbo and 964 pumps.
Today we have a plethora of options from Carrera, to 964 to GT3 and even aftermarket pumps.
We still maximize the flow whenever possible, even in modern day pumps, on every engine we build.

[PeteKz]

Neil, It’s common on many oil pumps in other engines too. The porting may look ugly, but it may be functional. Can’t know just by looking at it. If the end clearance is too large, then obviously reject it. If the end clearance is out of spec, i would expect the gear/housing is too. I would not want it in my engine.

[Neil Harvey]

Figured this is what was attempted. Is there any data available by those that do this to back up the reasoning.

Trying to understand how this will change flow rates in a positive displacement pump?
I assume the pumps efficiency is what the company is trying to increase. Not here in this particular pump. As the rotational speed is set by the engines RPM, efficiency is the only adder than could be increased.

Understand that in some cases, porting and polishing could help reduce fluid frictional losses, but I think this would only have an affect in a "port" of longer length. Not in this situation. Unless there is data showing it does help.

Checking and making sure the gear clearances are tight is way more important in pumps like this. The output side oil under pressure wants to migrate back to the suction side by vacuum and pressure.

In this pump, the clearances were horrible so any added flow this pump was intended to make would be lost by clearance issues.

Is this one of these things that was done and is kept "been done" thinking it does make a difference. So much of the Porsche world is based on historical thinking that was never backed up with test data.

When I saw this, it took my breathe away. Both in the quality of the work and the idea?

[PeteKz]

I have seen data tables in several performance books, but those were for VW and American iron. If you are familiar with Gene Berg VW performance and racing, he did this mod to VW oil pumps. Given his success at racing, i would trust that he did his homework. I have not seen such information for 911 pumps.

Regarding positive displacement pumps and how that could improve volume flow, consider two things: 1. If the oil has to make a turn around a sharp corner on the inlet side, that can induce cavitation, which will reduce output. 2. As you observed, some oil leaks around the gears/housing. If the outlet pressure is reduced by making a smoother exit port, then the pressure pushing the oil back around the gears/housing will also be reduced, and reduce the leakage.

[Neil Harvey]

Originally Posted by PeteKz

I have seen data tables in several performance books, but those were for VW and American iron. If you are familiar with Gene Berg VW performance and racing, he did this mod to VW oil pumps. Given his success at racing, i would trust that he did his homework. I have not seen such information for 911 pumps.

Regarding positive displacement pumps and how that could improve volume flow, consider two things: 1. If the oil has to make a turn around a sharp corner on the inlet side, that can induce cavitation, which will reduce output. 2. As you observed, some oil leaks around the gears/housing. If the outlet pressure is reduced by making a smoother exit port, then the pressure pushing the oil back around the gears/housing will also be reduced, and reduce the leakage.

All good points.

What you are considering is the pump efficiency. I think your points are valid but maybe not in a 911 pump. I would want to see test data showing that in these 911 pumps that this mod makes any difference.

As for cavitation in these pumps, I expect to see that happening on the scavenge side but not at a level where it causes damage. Or pumps would be coming apart. On the supply side, if that happens you have major oiling issues. One of the reasons for having the tank higher than the pump inlet.

I think this could be one of these many things done that is thought to make difference but doesn't. You can put theory against this but you can poke holes in that too. Testing is the only way to know if this makes a difference.

I tested the oil flow V pressure years ago with the AV pump. Quite involved with a lot of test equipment. Did this on the dyno but the data we recorded had too many variables . The only way to do this is to control the temp, pump speed and pressure. A running engine on the dyno was not accurate enough.

What caught my eye was the quality. Maybe it does not work and maybe it does not hurt either. Its saving grace.

Did not want to find fault or disparage anyone's work. Just trying to understand the thought process. This is something we have never done, heard of and the first time seeing.